EPE Day 01 Student Explanation Copy - English Only

EPE Day 01 - Student Explanation Copy (English Only)

100 True/False statements | simple English explanations | key medical terms | exam points

EXTERNAL PHARMACY EXAMINATION - DAY 01

Student Explanation Copy - English Only

Pharmacokinetics, Pharmacodynamics & Medicine Safety

100 statements - TRUE/FALSE answer + clear, student-friendly English explanation + important medical/pharmaceutical terms + exam point. This edition is designed for students who prefer to study fully in English.

How to use this copy effectively

This is not only an answer sheet. Read each statement and decide TRUE or FALSE by yourself first. Then open the explanation and check your reasoning.

  1. Read the statement carefully - Look for absolute words such as always, never, only and every.
  2. Decide TRUE or FALSE - Before looking at the answer, try to give one short reason in your own words.
  3. Read the easy explanation - Make sure you understand the medical/pharmaceutical terms, not only the final answer.
  4. Lock the exam rule - Use the Exam point box as the corrected rule that you should remember for the examination.

Quick glossary - understand these terms first

Systemic circulation The body-wide blood circulation that carries a drug to tissues after it enters the bloodstream.
Bioavailability (F) The fraction or percentage of an administered dose that reaches the systemic circulation as unchanged drug.
AUC Area under the plasma concentration-time curve. It is a major measure of total systemic drug exposure over time.
First-pass effect Presystemic metabolism in the gut wall and/or liver that can reduce the amount of unchanged oral drug reaching systemic circulation.
Volume of distribution (Vd) An apparent volume that relates the amount of drug in the body to the measured plasma concentration. It gives an idea of how extensively the drug distributes outside plasma.
Clearance (Cl) The body's efficiency in removing a drug from plasma, usually expressed as a volume per unit time such as L/hour or mL/min.
Half-life (t½) The time required for the amount or concentration of a drug to decrease by 50% under the relevant kinetic conditions.
Steady state The repeated-dosing condition in which the average rate of drug input equals the average rate of elimination, producing a stable concentration pattern.
Loading dose An initial dose used to reach a target drug concentration more rapidly.
Maintenance dose A repeated dose regimen used to replace drug being eliminated and maintain the desired concentration or effect.
Agonist A drug or ligand that binds to a receptor and activates it to produce a response.
Antagonist A drug or ligand that binds to a receptor and blocks or reduces the action of an agonist.
Potency How much dose or concentration is required to produce a particular effect.
Efficacy The maximum effect that a drug can produce in a given system.
Therapeutic index A measure that compares toxic and effective doses and gives a general idea of the drug's safety margin.
Free drug The unbound fraction of drug in plasma. It is generally more readily available for distribution, receptor binding, metabolism and filtration.

This glossary is added to support student understanding. The original Day 01 statement wording and TRUE/FALSE answer keys are preserved.

01. Bioavailability and exposure

Big picture

  • Bioavailability is broader than oral absorption: it describes how much unchanged drug becomes available in the systemic circulation.
  • Absolute bioavailability uses intravenous (IV) administration as the reference because IV drug enters systemic circulation directly.
  • AUC measures total exposure, Cmax is the peak concentration, and Tmax is the time taken to reach that peak. These are different parameters.
A. Absolute bioavailability compares systemic exposure after an extravascular dose with exposure after an intravenous dose.
TRUEQuick reason: IV dosing provides the reference because drug enters the systemic circulation directly.

Easy explanation: Absolute bioavailability asks how much systemic exposure is obtained from a non-IV route, such as oral, IM or SC administration, compared with IV administration. IV is the reference because it delivers drug directly into systemic blood without an absorption barrier. If the oral and IV doses are different, the dose difference must also be accounted for in the calculation.

Exam point: Absolute bioavailability = non-IV exposure compared with IV exposure.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Absolute bioavailability = non-IV exposure compared with IV exposure.
B. An intravenous dose has 100% bioavailability by definition.
TRUEQuick reason: There is no absorption step before systemic entry.

Easy explanation: With an IV dose, the drug is placed directly into the systemic circulation, so there is no loss during an absorption step. Therefore IV bioavailability is defined as F = 1, or 100%. This does not mean the drug can never be eliminated later; it only describes entry into systemic circulation.

Exam point: IV administration: F = 1 (100%).
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: IV administration: F = 1 (100%).
C. First-pass metabolism increases oral bioavailability.
FALSEQuick reason: Presystemic gut-wall or hepatic metabolism usually reduces the fraction reaching systemic circulation.

Easy explanation: After an oral drug is absorbed from the intestine, some of it may be metabolised in the intestinal wall and liver before it reaches systemic blood. This presystemic or first-pass metabolism removes unchanged drug, so it usually decreases oral bioavailability rather than increasing it.

Exam point: Correct rule: Extensive first-pass metabolism reduces oral bioavailability.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Extensive first-pass metabolism reduces oral bioavailability.
D. Area under the plasma concentration-time curve (AUC) is used to assess the extent of systemic exposure.
TRUEQuick reason: AUC integrates concentration over time and is a principal exposure measure.

Easy explanation: AUC represents the area under the plasma concentration-time curve. It combines both how high the concentration is and how long the drug remains present, so it is a useful measure of total systemic exposure. A larger AUC generally means greater overall exposure, assuming the comparison is appropriate.

Exam point: AUC = overall/total systemic exposure.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: AUC = overall/total systemic exposure.
E. Cmax alone completely describes both the rate and extent of absorption.
FALSEQuick reason: Cmax is useful but must be interpreted with AUC, Tmax and the clinical context.

Easy explanation: Cmax tells us only the highest measured plasma concentration. The rate of absorption is interpreted with information such as Cmax and Tmax, while the extent of exposure is assessed mainly with AUC. Therefore Cmax by itself cannot completely describe both rate and extent of absorption.

Exam point: Correct rule: Use Cmax/Tmax for rate clues and AUC for extent of exposure.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Use Cmax/Tmax for rate clues and AUC for extent of exposure.

02. Factors affecting absorption

Big picture

  • For a solid oral medicine, the usual sequence is disintegration -> dissolution -> absorption across the gastrointestinal membrane.
  • Absorption can be affected by pH, gastric emptying, intestinal motility, surface area, blood flow, food and formulation.
  • In True/False questions, distinguish cautious wording such as may affect from absolute wording such as always or never.
A. For many drugs, the unionised form crosses lipid membranes more readily than the ionised form.
TRUEQuick reason: Unionised molecules are generally more lipid soluble, although transporters and formulation also matter.

Easy explanation: Cell membranes are mainly lipid structures, so many neutral or unionised drug molecules cross by passive diffusion more easily than ionised molecules. However, real absorption also depends on factors such as pH, pKa, surface area, transporters and the formulation, so this is a general rule rather than the whole story.

Exam point: Unionised form generally crosses lipid membranes more readily.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Unionised form generally crosses lipid membranes more readily.
B. All orally administered medicines are absorbed mainly from the stomach.
FALSEQuick reason: The small intestine is the major absorption site for many medicines because of its large surface area.

Easy explanation: The stomach can absorb some drugs, but for many orally administered medicines the small intestine is the major absorption site. Its very large surface area, villi and microvilli, and good blood supply make it highly efficient for absorption.

Exam point: Correct rule: Many orally administered drugs are absorbed mainly from the small intestine.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Many orally administered drugs are absorbed mainly from the small intestine.
C. Gastric emptying can alter the rate at which a medicine reaches the small intestine.
TRUEQuick reason: A change in gastric emptying can therefore change the rate of absorption.

Easy explanation: Many drugs are absorbed mainly after they reach the small intestine. If gastric emptying is fast, the drug may reach this major absorption site sooner; if gastric emptying is slow, onset and Tmax may be delayed. Therefore gastric emptying often affects the rate rather than simply the final amount absorbed.

Exam point: Gastric emptying mainly influences how quickly drug reaches the main intestinal absorption site.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Gastric emptying mainly influences how quickly drug reaches the main intestinal absorption site.
D. Food can never alter medicine absorption.
FALSEQuick reason: Food can change dissolution, gastric emptying, pH, interactions and sometimes the extent of absorption.

Easy explanation: Food can alter drug absorption in several ways: it may slow gastric emptying, change gastrointestinal pH, increase bile secretion, form complexes with a drug, or change dissolution. Depending on the medicine, food may increase, decrease, delay or have little effect on absorption. That is why the word never makes the statement incorrect.

Exam point: Correct rule: Food may increase, decrease, delay, or occasionally not affect absorption depending on the drug.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Food may increase, decrease, delay, or occasionally not affect absorption depending on the drug.
E. Dissolution may become a limiting step before a solid oral medicine can be absorbed.
TRUEQuick reason: Drug must normally be in solution before membrane permeation.

Easy explanation: A solid tablet or capsule usually has to disintegrate and then the drug particles must dissolve in gastrointestinal fluid before molecules can cross the intestinal membrane. If a drug is poorly soluble, dissolution can become the slowest or rate-limiting step and therefore slow or reduce absorption.

Exam point: Solid dosage form: disintegration -> dissolution -> membrane absorption.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Solid dosage form: disintegration -> dissolution -> membrane absorption.

03. First-pass effect

Big picture

  • After oral absorption, drug may pass through the intestinal wall and portal circulation to the liver before reaching systemic circulation.
  • Extensive presystemic metabolism can reduce the amount of unchanged drug that finally reaches the blood and therefore lower oral bioavailability.
  • IV administration bypasses presystemic first-pass loss, while sublingual administration can also avoid much of hepatic first-pass metabolism.
A. The first-pass effect may involve metabolism in the intestinal wall and liver before systemic circulation is reached.
TRUEQuick reason: Both sites can contribute to presystemic loss.

Easy explanation: The first-pass effect is a presystemic loss that can occur before an orally absorbed drug reaches the general circulation. Enzymes in the intestinal wall and the liver can both metabolise the drug during this journey. Therefore both sites can contribute to reduced systemic availability.

Exam point: First-pass effect can occur in gut wall and liver before systemic entry.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: First-pass effect can occur in gut wall and liver before systemic entry.
B. The first-pass effect affects an intravenous dose to the same extent as an oral dose.
FALSEQuick reason: An IV dose enters systemic circulation directly and does not undergo presystemic absorption loss.

Easy explanation: An IV dose enters systemic circulation directly, so it does not pass through an absorption step and portal first-pass route before systemic entry. The drug may later be metabolised by the liver during normal circulation, but that later metabolism is not called first-pass loss.

Exam point: Correct rule: IV administration avoids presystemic first-pass loss.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: IV administration avoids presystemic first-pass loss.
C. Extensive first-pass metabolism can reduce oral bioavailability.
TRUEQuick reason: Less unchanged drug reaches systemic blood.

Easy explanation: If a large fraction of an oral dose is metabolised in the gut wall or liver before systemic entry, less unchanged drug reaches the blood. This lowers F, the oral bioavailability. Therefore extensive first-pass metabolism is an important cause of low oral bioavailability.

Exam point: More first-pass loss -> less unchanged drug reaching systemic circulation.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: More first-pass loss -> less unchanged drug reaching systemic circulation.
D. Sublingual administration can avoid much of the hepatic first-pass effect.
TRUEQuick reason: Venous drainage from the oral mucosa largely enters systemic circulation directly.

Easy explanation: Drug absorbed through the sublingual mucosa largely enters systemic venous blood directly instead of first travelling through the portal vein to the liver. This allows much of the hepatic first-pass effect to be avoided and can produce a rapid effect for suitable drugs such as nitroglycerin.

Exam point: Sublingual route largely bypasses hepatic first-pass metabolism.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Sublingual route largely bypasses hepatic first-pass metabolism.
E. Rectal administration always avoids first-pass metabolism completely.
FALSEQuick reason: Rectal venous drainage is mixed; avoidance is incomplete and depends on the site of absorption.

Easy explanation: Rectal venous drainage is mixed. Drug absorbed from some parts of the rectum may enter systemic circulation directly, while drug from other parts may drain into the portal circulation. Therefore rectal administration may partially avoid first-pass metabolism, but it does not always avoid it completely.

Exam point: Correct rule: Rectal administration may partially avoid first-pass metabolism, not always completely.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Rectal administration may partially avoid first-pass metabolism, not always completely.

04. Volume of distribution

Big picture

  • Volume of distribution (Vd) is an apparent mathematical volume, not a real anatomical body compartment.
  • A low Vd usually suggests that much of the drug remains in plasma or extracellular fluid, whereas a high Vd can suggest extensive tissue distribution or binding.
  • Vd is an important determinant of loading dose because a larger apparent distribution space usually requires more drug to reach the same target plasma concentration.
A. Apparent volume of distribution relates the amount of drug in the body to its measured plasma concentration.
TRUEQuick reason: Vd is an apparent proportionality term, not necessarily a real anatomical volume.

Easy explanation: Vd is calculated by relating the amount of drug in the body to the measured plasma concentration. It is called an apparent volume because it is a mathematical relationship, not a physical container inside the body. A high or low Vd helps us understand how the drug is distributed relative to plasma.

Exam point: Vd is an apparent volume linking amount in body to plasma concentration.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Vd is an apparent volume linking amount in body to plasma concentration.
B. A very large apparent volume of distribution usually means that the drug is confined to plasma.
FALSEQuick reason: A large Vd usually suggests extensive tissue distribution or tissue binding.

Easy explanation: If a drug is mainly confined to plasma, its plasma concentration tends to be relatively high and its Vd tends to be small. A very large Vd usually means that a large proportion of the drug has moved into tissues or is strongly tissue-bound, leaving a lower concentration in plasma.

Exam point: Correct rule: Large Vd usually suggests extensive tissue distribution, not plasma confinement.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Large Vd usually suggests extensive tissue distribution, not plasma confinement.
C. Only protein-bound drug readily crosses membranes and produces pharmacological effects.
FALSEQuick reason: The unbound fraction is generally available for diffusion, receptor binding, filtration and metabolism.

Easy explanation: Protein-bound drug is usually not the fraction that freely crosses membranes or immediately interacts with receptors. The free or unbound fraction is generally more readily available for tissue distribution, receptor binding, metabolism and glomerular filtration. Therefore the statement has the relationship reversed.

Exam point: Correct rule: Unbound drug is generally the readily diffusible and pharmacologically available fraction.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Unbound drug is generally the readily diffusible and pharmacologically available fraction.
D. Hypoalbuminaemia may increase the unbound fraction of a highly albumin-bound drug.
TRUEQuick reason: Fewer binding sites can increase the free fraction, especially for some acidic drugs.

Easy explanation: Albumin provides binding sites for many drugs. When albumin is low, a highly albumin-bound drug may have fewer available binding sites, so the free fraction can increase. This is why total concentration may be misleading in some patients with hypoalbuminaemia.

Exam point: Low albumin can increase the free fraction of highly albumin-bound drugs.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Low albumin can increase the free fraction of highly albumin-bound drugs.
E. Extensive tissue binding can increase apparent volume of distribution.
TRUEQuick reason: Plasma concentration becomes low relative to the total amount in the body.

Easy explanation: When a drug binds extensively to tissues, much of the total amount in the body is outside plasma, so the measured plasma concentration becomes relatively low. Because Vd is amount in body divided by plasma concentration, this pattern can produce a large apparent Vd.

Exam point: More tissue binding -> lower plasma concentration relative to body amount -> larger Vd.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: More tissue binding -> lower plasma concentration relative to body amount -> larger Vd.

05. Clearance

Big picture

  • Clearance is not simply the amount of drug removed per hour. It is the apparent volume of plasma cleared of drug per unit time.
  • Total body clearance can include renal, hepatic and other organ clearances.
  • Clearance is closely linked to maintenance dosing because the maintenance dose rate must replace drug that is being eliminated.
A. Clearance is the theoretical volume of plasma cleared of drug per unit time.
TRUEQuick reason: It describes elimination efficiency and has units of volume per time.

Easy explanation: Clearance describes how efficiently the body removes drug from plasma. It is expressed as an apparent volume of plasma cleared of drug per unit time, such as L/hour or mL/min. Do not confuse clearance with the actual mass of drug removed per hour, which is an elimination rate.

Exam point: Clearance = elimination efficiency expressed as volume/time.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Clearance = elimination efficiency expressed as volume/time.
B. Total body clearance may be considered the sum of relevant organ clearances.
TRUEQuick reason: Renal, hepatic and other clearances can contribute to total clearance.

Easy explanation: Different organs can contribute to elimination. For many drugs, renal clearance and hepatic clearance are the main components, with other routes contributing when relevant. Conceptually, total body clearance is the sum of these relevant organ clearances.

Exam point: CLtotal = CLrenal + CLhepatic + other relevant clearances.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: CLtotal = CLrenal + CLhepatic + other relevant clearances.
C. A reduction in clearance necessarily shortens elimination half-life.
FALSEQuick reason: If Vd is unchanged, reduced clearance prolongs half-life.

Easy explanation: For a simple linear model, half-life is approximately t½ = 0.693 x Vd / Cl. If Vd is unchanged and clearance falls, drug is removed more slowly and half-life becomes longer, not shorter. The statement therefore gives the opposite relationship.

Exam point: Correct rule: Lower clearance usually prolongs half-life if Vd is unchanged.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Lower clearance usually prolongs half-life if Vd is unchanged.
D. The maintenance dose rate is closely related to clearance and the target steady-state concentration.
TRUEQuick reason: Dose rate must replace drug eliminated per unit time.

Easy explanation: At steady state, the average maintenance dose rate must replace the drug that is being eliminated. A higher clearance means drug is removed faster and usually requires a higher dose rate to maintain the same target concentration. A lower clearance often requires a lower dose rate or longer interval.

Exam point: Maintenance dose rate mainly follows clearance, target Css and bioavailability.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Maintenance dose rate mainly follows clearance, target Css and bioavailability.
E. Renal impairment may reduce clearance of a medicine eliminated mainly by the kidneys.
TRUEQuick reason: Dose or interval adjustment may therefore be needed.

Easy explanation: If a medicine is mainly eliminated by the kidneys, reduced kidney function can reduce its renal clearance. The drug may then accumulate and increase toxicity risk. Dose reduction, a longer dosing interval, or both may be required depending on the drug and the patient.

Exam point: Renal impairment can reduce renal clearance and increase accumulation risk.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Renal impairment can reduce renal clearance and increase accumulation risk.

06. Elimination half-life

Big picture

  • For a simple one-compartment first-order model, half-life is related to both Vd and clearance: t½ = 0.693 x Vd / Cl.
  • If Vd increases, half-life tends to increase; if clearance increases, half-life tends to decrease, assuming the other factor is unchanged.
  • Half-life helps estimate accumulation, washout and the time needed to approach a new steady state after a dose change.
A. For a one-compartment first-order model, half-life is proportional to Vd and inversely proportional to clearance.
TRUEQuick reason: The common relationship is t1/2 = 0.693 x Vd / CL.

Easy explanation: In the one-compartment first-order model, half-life depends on both how widely the drug is distributed and how efficiently it is cleared. The relationship t½ = 0.693 x Vd / Cl shows that increasing Vd tends to lengthen half-life, while increasing clearance tends to shorten it, if the other factor stays the same.

Exam point: t1/2 = 0.693 x Vd / CL.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: t1/2 = 0.693 x Vd / CL.
B. After one elimination half-life, approximately 50% of the relevant drug amount remains.
TRUEQuick reason: This follows first-order exponential decline.

Easy explanation: Half-life means the time required for the relevant amount or concentration to fall by half. Under first-order kinetics, after one half-life about 50% remains; after two, about 25% remains; after three, about 12.5% remains. The decline is exponential, not a fixed amount each time.

Exam point: 1 half-life -> 50% remains; 2 -> 25%; 3 -> 12.5%.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: 1 half-life -> 50% remains; 2 -> 25%; 3 -> 12.5%.
C. Near steady state is commonly approached after about four to five half-lives.
TRUEQuick reason: This corresponds to roughly 94-97% of the final plateau in linear kinetics.

Easy explanation: With repeated dosing in linear kinetics, the concentration approaches its final plateau gradually. After about four half-lives it is roughly 94% of the final steady-state level and after five about 97%. This is why 4-5 half-lives is a useful practical rule.

Exam point: Practical near steady state: about 4-5 half-lives.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Practical near steady state: about 4-5 half-lives.
D. Elimination half-life is unrelated to clearance.
FALSEQuick reason: Clearance is a major determinant of half-life.

Easy explanation: Clearance is one of the major determinants of half-life. If clearance decreases while Vd remains similar, elimination slows and half-life increases. Therefore it is incorrect to say that half-life is unrelated to clearance.

Exam point: Correct rule: Half-life depends on both Vd and clearance.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Half-life depends on both Vd and clearance.
E. Half-life helps predict accumulation and the time course after a dosage change.
TRUEQuick reason: It informs dosing interval, washout and time to a new plateau.

Easy explanation: Half-life helps predict how much drug remains between doses, how long accumulation takes, how long washout takes, and how quickly concentration adjusts after a dose change. A new steady-state pattern is commonly approached over about 4-5 half-lives.

Exam point: Half-life predicts accumulation, washout and time to a new steady state.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Half-life predicts accumulation, washout and time to a new steady state.

07. Steady state and accumulation

Big picture

  • Accumulation occurs when a new dose is given while some drug from previous doses is still present in the body.
  • With linear first-order kinetics, practical steady state is usually approached after about 4-5 half-lives.
  • Steady state does not mean a perfectly flat concentration: peaks and troughs can still occur within each dosing interval.
A. At steady state, the average rate of drug input equals the average rate of drug elimination.
TRUEQuick reason: Concentrations may still fluctuate within each dosing interval.

Easy explanation: At steady state, the body is not necessarily holding one perfectly constant plasma concentration. Concentration may rise after a dose and fall before the next dose, creating peaks and troughs. What is balanced is the average rate of drug entering the body and the average rate being eliminated.

Exam point: Steady state: average input rate equals average elimination rate.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Steady state: average input rate equals average elimination rate.
B. Steady state is normally achieved immediately after the first maintenance dose.
FALSEQuick reason: Repeated dosing usually requires several half-lives to approach steady state.

Easy explanation: The first maintenance dose does not normally create the final steady-state concentration. Drug from repeated doses accumulates progressively until input and elimination balance. In linear first-order kinetics, this usually takes about 4-5 half-lives.

Exam point: Correct rule: Maintenance dosing usually approaches steady state over several half-lives.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Maintenance dosing usually approaches steady state over several half-lives.
C. Under linear kinetics, time to steady state is determined mainly by elimination half-life.
TRUEQuick reason: Changing the dose changes the plateau concentration more than the time constant.

Easy explanation: When kinetics are linear, the dose mainly determines the final steady-state level, while the drug's elimination half-life mainly determines how quickly that level is approached. Doubling the dose can raise the plateau, but it does not normally halve the time needed to reach it.

Exam point: In linear kinetics, dose changes the level; half-life mainly determines the time to reach it.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: In linear kinetics, dose changes the level; half-life mainly determines the time to reach it.
D. A loading dose changes the drug's elimination half-life.
FALSEQuick reason: A loading dose raises concentration rapidly but does not normally change the drug's elimination kinetics.

Easy explanation: A loading dose is used to raise the concentration quickly at the beginning of therapy. It does not normally change the drug's intrinsic Vd or clearance, so it does not change the elimination half-life under ordinary linear conditions.

Exam point: Correct rule: Loading dose changes starting concentration, not the elimination half-life.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Loading dose changes starting concentration, not the elimination half-life.
E. Accumulation occurs when subsequent doses are given before the previous dose has been fully eliminated.
TRUEQuick reason: The extent depends on half-life, interval and kinetics.

Easy explanation: Accumulation happens when a new dose is given while residual drug from previous doses is still present. The amount of accumulation depends strongly on the half-life and the dosing interval. A long half-life or a short interval generally leaves more residual drug at the time of the next dose.

Exam point: Accumulation = residual drug from previous doses + new doses.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Accumulation = residual drug from previous doses + new doses.

08. Loading dose

Big picture

  • A loading dose is used when we want to reach a target concentration rapidly instead of waiting several half-lives.
  • The basic relationship is approximately: Loading dose = Vd x target concentration / bioavailability (F).
  • Loading dose depends mainly on Vd, target concentration and bioavailability; clearance is more directly important for maintenance dosing.
A. A loading dose is used to reach a target concentration rapidly.
TRUEQuick reason: It is useful when waiting several half-lives would be clinically undesirable.

Easy explanation: A loading dose is useful when reaching the target concentration quickly is clinically important. Without it, a long half-life drug may require several days of maintenance dosing before reaching the desired concentration. The loading dose gives a larger initial amount to fill the apparent distribution space rapidly.

Exam point: Loading dose = reach target concentration rapidly.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Loading dose = reach target concentration rapidly.
B. Loading dose is determined mainly by clearance rather than volume of distribution.
FALSEQuick reason: Loading dose is driven mainly by target concentration, Vd and bioavailability.

Easy explanation: The conceptual loading-dose relationship is LD = Vd x target concentration / F. This shows why Vd and bioavailability are central to loading dose. Clearance is much more directly related to the maintenance dose rate because it describes ongoing drug removal.

Exam point: Correct rule: Loading dose depends mainly on Vd, target concentration and bioavailability.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Loading dose depends mainly on Vd, target concentration and bioavailability.
C. A medicine with a long half-life may be a candidate for a loading dose when rapid effect is required.
TRUEQuick reason: Otherwise the target concentration may take a long time to reach.

Easy explanation: A long half-life means that maintenance dosing alone may take a long time to build up to the target level. If a rapid therapeutic effect is needed and the medicine is appropriate for loading, a loading dose may be used to avoid waiting several half-lives.

Exam point: Long half-life + urgent target effect -> loading dose may be useful.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Long half-life + urgent target effect -> loading dose may be useful.
D. A larger apparent volume of distribution may require a larger loading dose for the same target concentration.
TRUEQuick reason: More drug is needed to achieve the same plasma target when Vd is larger.

Easy explanation: Think of Vd as the drug's effective distribution space. If that space is larger, more total drug is needed to produce the same target plasma concentration. Therefore, with the same target concentration and bioavailability, a larger Vd generally requires a larger loading dose.

Exam point: Larger Vd generally -> larger loading dose for the same target concentration and F.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Larger Vd generally -> larger loading dose for the same target concentration and F.
E. Renal impairment always requires a smaller loading dose.
FALSEQuick reason: Renal impairment more predictably affects maintenance dosing; loading dose depends on Vd and the clinical situation.

Easy explanation: Renal impairment often reduces clearance, so it commonly affects maintenance dosing. But loading dose is determined mainly by Vd, target concentration and F. Renal impairment does not automatically mean the loading dose must always be smaller, especially if Vd has not changed in the same way.

Exam point: Correct rule: Renal impairment commonly affects maintenance dose more directly than loading dose.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Renal impairment commonly affects maintenance dose more directly than loading dose.

09. Maintenance dosing

Big picture

  • The purpose of maintenance dosing is to replace drug that is continuously being eliminated so that the desired average concentration is maintained.
  • The basic relationship is approximately: Maintenance dose rate = Clearance x target concentration / bioavailability (F).
  • If renal or hepatic impairment lowers clearance, the dose or dosing interval may need adjustment to prevent accumulation.
A. Maintenance dosing replaces drug removed by clearance.
TRUEQuick reason: The dose rate is linked to target concentration, clearance and bioavailability.

Easy explanation: Once a target concentration has been reached, the body continues to eliminate drug. Maintenance dosing replaces this ongoing loss so that the average concentration remains near the desired level. That is why maintenance dose rate is closely related to clearance.

Exam point: Maintenance dose rate replaces ongoing elimination.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Maintenance dose rate replaces ongoing elimination.
B. If clearance falls and all other factors are unchanged, a lower maintenance dose rate may be needed.
TRUEQuick reason: Otherwise accumulation and toxicity may occur.

Easy explanation: If clearance falls, drug leaves the body more slowly. Continuing the same previous dose rate can make drug input exceed elimination, leading to accumulation and possible toxicity. A lower dose rate or a longer interval may therefore be needed.

Exam point: Lower clearance often requires lower maintenance dose rate or a longer interval.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Lower clearance often requires lower maintenance dose rate or a longer interval.
C. Maintenance dose is determined only by volume of distribution.
FALSEQuick reason: Vd is more central to loading dose; clearance is central to maintenance dose rate.

Easy explanation: Vd is especially important for loading dose because it describes distribution. Ongoing maintenance dose rate is driven mainly by how quickly drug is eliminated, which is clearance, together with the target steady-state concentration and bioavailability. Therefore maintenance dose is not determined only by Vd.

Exam point: Correct rule: Clearance is the key PK determinant of maintenance dose rate.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Clearance is the key PK determinant of maintenance dose rate.
D. Changing the dosing interval can change peak-to-trough fluctuation.
TRUEQuick reason: Shorter intervals usually produce smaller fluctuations for the same total daily dose.

Easy explanation: The dosing interval affects how much concentration rises and falls between doses. Smaller, more frequent doses often produce smaller peak-to-trough fluctuations for the same total daily dose, while longer intervals can produce higher peaks and lower troughs.

Exam point: Dosing interval affects peak-trough fluctuation.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Dosing interval affects peak-trough fluctuation.
E. A dosing interval that is short relative to half-life can produce accumulation.
TRUEQuick reason: A significant fraction remains when the next dose is administered.

Easy explanation: If the dosing interval is short compared with the drug's half-life, a substantial amount of the previous dose remains when the next dose is given. Repeated overlap between residual drug and new doses produces accumulation.

Exam point: Short interval relative to half-life -> more residual drug -> accumulation.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Short interval relative to half-life -> more residual drug -> accumulation.

10. First-order elimination

Big picture

  • In first-order elimination, the same fraction or percentage of drug is eliminated during each equal time interval.
  • The actual amount removed per hour becomes smaller as the drug concentration falls.
  • Under linear first-order conditions, elimination half-life is approximately constant and concentration declines exponentially after input stops.
A. A constant fraction of the drug is eliminated per unit time.
TRUEQuick reason: The amount removed falls as concentration falls.

Easy explanation: First-order elimination means that the same fraction or percentage of the drug is eliminated during each equal time period. For example, if 50% is removed during one half-life, 50% of what remains is removed during the next half-life. The actual number of milligrams removed therefore becomes smaller as the amount falls.

Exam point: First-order = constant fraction per unit time.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: First-order = constant fraction per unit time.
B. Most medicines show approximately first-order elimination within their usual therapeutic range.
TRUEQuick reason: Elimination pathways are not saturated in this range for many medicines.

Easy explanation: For many medicines at usual therapeutic concentrations, elimination pathways are not saturated. The elimination rate therefore changes approximately in proportion to drug concentration, producing first-order behaviour over that range.

Exam point: Most drugs are approximately first-order within usual therapeutic concentrations.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Most drugs are approximately first-order within usual therapeutic concentrations.
C. Half-life is constant when first-order linear kinetics apply.
TRUEQuick reason: The same fraction is lost in each equal time interval.

Easy explanation: Because the same fraction is removed in each equal time interval, the time needed for concentration to fall from 100 to 50 is approximately the same as the time from 50 to 25. That repeated interval is the half-life, so it is approximately constant in linear first-order kinetics.

Exam point: First-order linear kinetics -> approximately constant half-life.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: First-order linear kinetics -> approximately constant half-life.
D. A constant amount of drug is eliminated per unit time during first-order elimination.
FALSEQuick reason: A constant fraction, not a constant amount, is eliminated.

Easy explanation: A constant amount removed per unit time is a zero-order feature, not a first-order feature. In first-order elimination, the fraction is constant but the absolute amount removed per hour decreases as concentration falls.

Exam point: Correct rule: First-order = constant fraction; zero-order = constant amount.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: First-order = constant fraction; zero-order = constant amount.
E. Plasma concentration declines exponentially after input stops.
TRUEQuick reason: This is characteristic of first-order elimination.

Easy explanation: After drug input stops, first-order elimination produces an exponential decline in plasma concentration. The curve is not a straight line on a normal concentration-versus-time plot, although a logarithmic concentration plot can become linear.

Exam point: First-order decline is exponential with time.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: First-order decline is exponential with time.

11. Zero-order and capacity-limited elimination

Big picture

  • Elimination pathways such as enzymes or transport systems can become saturated when their maximum capacity is reached.
  • In a zero-order region, approximately the same amount of drug is eliminated per unit time rather than the same fraction.
  • Near saturation, even a small increase in dose can produce a disproportionately large increase in drug concentration or exposure.
A. A constant amount of drug is eliminated per unit time during zero-order elimination.
TRUEQuick reason: The pathway is operating at a capacity limit.

Easy explanation: When an elimination pathway is saturated, it is already working at its maximum capacity. Increasing the drug concentration cannot make the pathway remove proportionally more drug, so approximately the same amount may be eliminated per unit time. This is the key idea of zero-order elimination.

Exam point: Zero-order = approximately constant amount eliminated per unit time.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Zero-order = approximately constant amount eliminated per unit time.
B. Zero-order behaviour may appear when an elimination pathway is saturated.
TRUEQuick reason: The elimination rate can no longer rise proportionally with concentration.

Easy explanation: Enzymes and transporters have a finite capacity. Once they become saturated, the elimination rate can no longer rise in direct proportion to concentration. This creates capacity-limited, nonlinear or zero-order-like behaviour over the saturated range.

Exam point: Saturation can produce capacity-limited/zero-order behaviour.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Saturation can produce capacity-limited/zero-order behaviour.
C. A constant half-life is a defining feature of zero-order elimination.
FALSEQuick reason: The apparent half-life changes with concentration in zero-order kinetics.

Easy explanation: In zero-order elimination, a fixed amount rather than a fixed fraction is removed per unit time. Therefore the time needed to remove half of the drug depends on the starting concentration, and the apparent half-life is not constant as it is in first-order kinetics.

Exam point: Correct rule: Zero-order kinetics do not have a constant half-life.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Zero-order kinetics do not have a constant half-life.
D. Ethanol is a commonly taught example of approximate zero-order elimination over relevant concentrations.
TRUEQuick reason: Metabolic capacity becomes limiting.

Easy explanation: Ethanol is a classic teaching example because the enzymes responsible for its metabolism can operate near capacity over relevant concentrations. As a result, an approximately constant amount can be metabolised per unit time over that range.

Exam point: Classic teaching example: ethanol shows approximate capacity-limited/zero-order elimination over relevant ranges.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Classic teaching example: ethanol shows approximate capacity-limited/zero-order elimination over relevant ranges.
E. Near saturation, a small dose increase can cause a disproportionate rise in concentration.
TRUEQuick reason: Capacity-limited elimination makes exposure nonlinear.

Easy explanation: When the elimination pathway is close to saturation, it has little spare capacity. A small dose increase can then add much more drug than the body can remove proportionally, causing a large and sometimes unexpected rise in plasma concentration or exposure.

Exam point: Near saturation, small dose increases may cause large concentration increases.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Near saturation, small dose increases may cause large concentration increases.

12. Agonists and antagonists

Big picture

  • An agonist binds to a receptor and activates it, while an antagonist binds but blocks or reduces agonist action.
  • A reversible competitive antagonist competes at the agonist binding site, so increasing agonist concentration can sometimes overcome the block.
  • A partial agonist activates the receptor but produces a lower maximum response than a full agonist in the same system.
A. A full agonist has affinity and can produce a maximal receptor response in the test system.
TRUEQuick reason: It has intrinsic efficacy in addition to receptor binding.

Easy explanation: A full agonist must be able to bind to the receptor (affinity) and activate it effectively (efficacy). In the test system, it can produce the maximal response when enough receptors are activated. Binding alone is not enough to make a drug an agonist.

Exam point: Full agonist = affinity + sufficient efficacy to produce the system's maximal response.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Full agonist = affinity + sufficient efficacy to produce the system's maximal response.
B. A reversible competitive antagonist can shift an agonist concentration-response curve to the right.
TRUEQuick reason: More agonist may overcome the antagonism if the system remains surmountable.

Easy explanation: A reversible competitive antagonist competes with the agonist for the same receptor site. Because the competition is reversible, increasing the agonist concentration can often overcome the block, so a higher agonist concentration is needed for the same response and the curve shifts to the right.

Exam point: Competitive reversible antagonism: rightward shift, usually surmountable.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Competitive reversible antagonism: rightward shift, usually surmountable.
C. An antagonist must possess positive intrinsic efficacy.
FALSEQuick reason: A neutral antagonist binds without activating the receptor.

Easy explanation: A neutral antagonist binds to the receptor but does not activate it. Its intrinsic efficacy is essentially zero, and its role is to prevent or reduce agonist action. Therefore an antagonist does not need positive intrinsic efficacy.

Exam point: Correct rule: A neutral antagonist has affinity but essentially no positive intrinsic efficacy.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: A neutral antagonist has affinity but essentially no positive intrinsic efficacy.
D. A partial agonist can reduce the effect of a full agonist when both compete for the same receptors.
TRUEQuick reason: It occupies receptors but produces a lower response.

Easy explanation: A partial agonist activates the receptor but produces a smaller maximal response than a full agonist in the same system. When both are present, the partial agonist can occupy receptors that would otherwise be occupied by the full agonist, reducing the overall response.

Exam point: A partial agonist can behave functionally as an antagonist in the presence of a full agonist.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: A partial agonist can behave functionally as an antagonist in the presence of a full agonist.
E. A non-competitive or irreversible antagonist may reduce the maximum achievable response.
TRUEQuick reason: Its effect may not be overcome by simply increasing agonist concentration.

Easy explanation: An irreversible antagonist or a non-competitive block may reduce the number of functional receptors or interfere with signalling in a way that extra agonist cannot fully overcome. As a result, the maximum achievable response, Emax, may fall.

Exam point: Non-competitive/irreversible antagonism may reduce Emax.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Non-competitive/irreversible antagonism may reduce Emax.

13. Potency and efficacy

Big picture

  • Potency describes how much drug is needed to produce a given effect; efficacy describes the maximum effect the drug can produce.
  • A more potent drug is not automatically more efficacious.
  • Clinical drug choice must consider efficacy, safety, patient factors, interactions, dosage form and evidence - not potency alone.
A. Potency concerns the concentration or dose needed to produce a stated effect.
TRUEQuick reason: Lower EC50 or ED50 generally indicates greater potency in a comparable system.

Easy explanation: Potency answers the question: how much drug is needed to produce a particular effect? In comparable systems, a lower EC50 or ED50 usually means greater potency because less concentration or dose is required.

Exam point: Potency = how much drug is needed for a given effect.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Potency = how much drug is needed for a given effect.
B. Efficacy concerns the maximum effect a medicine can produce.
TRUEQuick reason: It is represented by Emax in a graded response system.

Easy explanation: Efficacy answers a different question: what is the greatest effect this drug can produce? On a graded concentration-response curve, this is represented by Emax, the plateau reached when increasing concentration no longer increases response.

Exam point: Efficacy = maximum achievable effect (Emax).
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Efficacy = maximum achievable effect (Emax).
C. A more potent medicine is always more efficacious.
FALSEQuick reason: Potency and maximum efficacy are different properties.

Easy explanation: A drug can produce a given effect at a low dose and therefore be very potent, yet still have a lower maximum effect than another drug. Potency is about dose requirement; efficacy is about maximum effect. The two properties must not be confused.

Exam point: Correct rule: Greater potency does not necessarily mean greater efficacy.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Greater potency does not necessarily mean greater efficacy.
D. EC50 is commonly used as an index of potency in a graded concentration-response curve.
TRUEQuick reason: It is the concentration giving 50% of the maximum response in that system.

Easy explanation: EC50 is the concentration that produces 50% of that drug's maximum response in a particular graded-response system. When two drugs are compared under the same conditions, the drug with the lower EC50 is generally considered more potent.

Exam point: Lower EC50 generally means greater potency in the same system.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Lower EC50 generally means greater potency in the same system.
E. Clinical medicine selection should be based on potency alone.
FALSEQuick reason: Efficacy, safety, patient factors, interactions, dosage form and cost also matter.

Easy explanation: The most potent drug is not automatically the best clinical choice. Treatment decisions also depend on efficacy, adverse effects, contraindications, patient factors, interactions, dosage form, adherence, cost and the quality of evidence.

Exam point: Correct rule: Clinical selection is multifactorial; potency alone is insufficient.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Clinical selection is multifactorial; potency alone is insufficient.

14. Therapeutic index and monitoring

Big picture

  • A narrow therapeutic index means the effective and toxic exposure ranges are relatively close, so small changes may matter clinically.
  • Therapeutic drug monitoring (TDM) is useful only for selected medicines and selected patients, not for every medicine.
  • A concentration result must always be interpreted together with the patient's clinical condition, organ function, interactions and timing of the sample.
A. A classical therapeutic index may be expressed as TD50 divided by ED50.
TRUEQuick reason: It compares a median toxic dose with a median effective dose.

Easy explanation: The classical therapeutic index compares a median toxic dose with a median effective dose: TI = TD50 / ED50. It is a conceptual way of describing how separated toxic and effective doses are. It should not be interpreted as a complete measure of safety for every patient.

Exam point: Therapeutic index (classical) = TD50 / ED50.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Therapeutic index (classical) = TD50 / ED50.
B. A larger therapeutic index generally indicates a wider safety margin.
TRUEQuick reason: There is greater separation between effective and toxic doses.

Easy explanation: If the toxic dose is much higher than the effective dose, the therapeutic index is larger and the separation between beneficial and harmful doses is wider. Therefore a larger TI generally suggests a wider safety margin.

Exam point: Larger TI generally means a wider margin between effective and toxic doses.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Larger TI generally means a wider margin between effective and toxic doses.
C. Medicines with a narrow therapeutic index often require closer dose individualisation or monitoring.
TRUEQuick reason: Small exposure changes may cause loss of effect or toxicity.

Easy explanation: With a narrow therapeutic index, relatively small changes in dose or exposure can move a patient from too little effect to toxicity. Changes in renal function, interactions or adherence can therefore be clinically important, so closer individualisation or monitoring may be required.

Exam point: Narrow therapeutic index -> small dosing/exposure changes may be clinically important.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Narrow therapeutic index -> small dosing/exposure changes may be clinically important.
D. The therapeutic window is identical in every patient.
FALSEQuick reason: Age, organ function, disease, interactions and sensitivity can alter the safe range.

Easy explanation: Patients do not all respond to the same concentration in exactly the same way. Age, kidney and liver function, disease, electrolytes, genetics, interactions and individual sensitivity can all shift the balance between benefit and toxicity. The therapeutic range is therefore a guide, not a fixed identical window for everyone.

Exam point: Correct rule: Therapeutic range is a guide, not an identical fixed window for every patient.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Therapeutic range is a guide, not an identical fixed window for every patient.
E. Digoxin is a commonly taught example of a medicine with a narrow safety margin.
TRUEQuick reason: Toxicity risk is affected by dose, renal function and electrolytes.

Easy explanation: Digoxin is commonly used as a teaching example of a medicine with a narrow safety margin. Toxicity risk is influenced by factors such as dose, renal function, electrolyte disturbances and drug interactions, so careful dosing and monitoring are important.

Exam point: Digoxin is a classic narrow-therapeutic-index teaching example.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Digoxin is a classic narrow-therapeutic-index teaching example.

15. Adverse drug reactions

Big picture

  • Adverse drug reactions (ADRs) can be predictable and dose-related or unusual and less predictable.
  • The terms side effect, allergy, intolerance and ADR are not identical. A true allergy is immune-mediated.
  • Serious or unexpected suspected ADRs are important for pharmacovigilance and should follow the applicable reporting pathway.
A. Type A adverse reactions are usually dose-related and predictable from pharmacology.
TRUEQuick reason: They are often common and may improve with dose reduction.

Easy explanation: Type A reactions are often described as Augmented reactions. They are usually predictable from the normal pharmacological action of the drug, tend to be dose-related and are relatively common. Reducing the dose may reduce the reaction when clinically appropriate.

Exam point: Type A ADR: predictable, dose-related, pharmacology-related.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Type A ADR: predictable, dose-related, pharmacology-related.
B. Type B adverse reactions are often uncommon and less predictable.
TRUEQuick reason: They may include unusual immune or idiosyncratic reactions.

Easy explanation: Type B reactions are often remembered as Bizarre reactions. They are generally less predictable, less clearly related to dose and can include immune-mediated or idiosyncratic reactions. They are usually less common than Type A reactions.

Exam point: Type B ADR: uncommon, less predictable, often non-dose-related.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Type B ADR: uncommon, less predictable, often non-dose-related.
C. Every side effect is an allergic reaction.
FALSEQuick reason: Many side effects are non-immune extensions of pharmacological action.

Easy explanation: A side effect does not automatically mean allergy. Many side effects, such as drowsiness or dry mouth, are predictable non-immune effects of the drug's pharmacology. A true drug allergy involves an immune mechanism.

Exam point: Correct rule: Side effects are not automatically allergies; true allergy is immune-mediated.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Side effects are not automatically allergies; true allergy is immune-mediated.
D. A true drug allergy may occur with a small dose after sensitisation.
TRUEQuick reason: Immune reactions are not simply proportional to therapeutic dose.

Easy explanation: After a patient has been sensitised, the immune system may respond strongly when the drug or a related antigen is encountered again. The triggering dose can be small because allergic reactions are not simply proportional to the normal therapeutic dose.

Exam point: After sensitisation, even a small re-exposure may trigger allergy.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: After sensitisation, even a small re-exposure may trigger allergy.
E. A medication error and an adverse drug reaction are identical concepts.
FALSEQuick reason: An error is a preventable process failure; an ADR is a harmful response at normal use, although errors can cause harm.

Easy explanation: A medication error is a preventable failure in prescribing, dispensing, administration or another medicine-use process. An ADR is a harmful unintended response associated with appropriate use of a medicine. Errors can cause harm, but the two concepts are not identical.

Exam point: Correct rule: Medication error = preventable process failure; ADR = harmful drug response during appropriate use.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Medication error = preventable process failure; ADR = harmful drug response during appropriate use.

16. Drug interactions

Big picture

  • Drug interactions can be pharmacokinetic, where ADME or drug exposure changes, or pharmacodynamic, where the effect changes without necessarily changing concentration.
  • Enzyme inhibition usually slows metabolism and can increase substrate exposure; enzyme induction usually increases metabolism and can reduce exposure.
  • An interaction is not automatically a reason to avoid a combination; the clinical significance and management depend on the medicines and the patient.
A. A pharmacokinetic interaction changes absorption, distribution, metabolism or excretion.
TRUEQuick reason: It changes drug exposure or concentration-time behaviour.

Easy explanation: A pharmacokinetic interaction changes what the body does to a drug - absorption, distribution, metabolism or excretion. This can alter concentration-time behaviour, including AUC, Cmax, half-life or overall exposure.

Exam point: Pharmacokinetic interaction = change in ADME/exposure.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Pharmacokinetic interaction = change in ADME/exposure.
B. A pharmacodynamic interaction can change effect without changing drug concentration.
TRUEQuick reason: Additive bleeding or sedation are common conceptual examples.

Easy explanation: A pharmacodynamic interaction changes the effect produced by drugs without necessarily changing their plasma concentrations. For example, two sedating medicines may cause excessive sedation because their effects add together, even if neither drug concentration changes.

Exam point: Pharmacodynamic interaction = effect changes without necessarily changing concentration.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Pharmacodynamic interaction = effect changes without necessarily changing concentration.
C. Enzyme induction can reduce exposure to a substrate metabolised by that enzyme.
TRUEQuick reason: Metabolic capacity increases, usually after a delay.

Easy explanation: An enzyme inducer increases the amount or activity of a metabolising enzyme. A substrate of that enzyme may then be metabolised faster, reducing its plasma concentration and exposure. Because new enzyme synthesis takes time, induction often develops and disappears gradually.

Exam point: Enzyme induction often increases metabolism and lowers substrate exposure.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Enzyme induction often increases metabolism and lowers substrate exposure.
D. Enzyme inhibition usually accelerates metabolism of the affected substrate.
FALSEQuick reason: Inhibition usually slows metabolism and can raise exposure.

Easy explanation: Enzyme inhibition usually does the opposite of the statement: it reduces or slows the activity of a metabolising enzyme. The affected substrate can then accumulate, increasing AUC and sometimes toxicity risk.

Exam point: Correct rule: Enzyme inhibition usually slows metabolism and may increase substrate exposure.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Enzyme inhibition usually slows metabolism and may increase substrate exposure.
E. Warfarin therapy can be affected by medicines, illness and major dietary changes.
TRUEQuick reason: INR monitoring and interaction checking are therefore important.

Easy explanation: Warfarin response can change because of interacting medicines, illness, liver function, antibiotics and major changes in dietary vitamin K intake. Because the anticoagulant effect can move in either direction, INR monitoring and careful interaction review are important.

Exam point: Warfarin requires careful INR and interaction monitoring.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Warfarin requires careful INR and interaction monitoring.

17. Protein binding and free drug

Big picture

  • The unbound or free drug fraction is generally the fraction most readily available for membrane crossing, receptor binding, metabolism and glomerular filtration.
  • Protein-binding displacement can temporarily increase the free fraction, but this does not automatically cause severe or prolonged toxicity.
  • Total plasma concentration and pharmacologically active free concentration are not always equivalent, especially when protein binding changes.
A. The unbound fraction is available for glomerular filtration.
TRUEQuick reason: Protein-bound drug is generally too large as a complex to be filtered.

Easy explanation: Albumin and other plasma proteins are generally too large to cross the glomerular filtration barrier freely. Therefore drug that is tightly bound to plasma protein is not readily filtered as a protein-drug complex, while the unbound fraction is available for glomerular filtration.

Exam point: Only unbound drug is normally available for glomerular filtration.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Only unbound drug is normally available for glomerular filtration.
B. Displacement from plasma proteins always causes prolonged severe toxicity.
FALSEQuick reason: Compensatory distribution and clearance often limit the effect; clinical significance depends on the drug.

Easy explanation: Displacing a highly bound drug from plasma proteins can temporarily increase its free fraction, but free drug can also redistribute into tissues or be cleared more rapidly. Whether the change is clinically important depends on the drug's therapeutic index, Vd, clearance and duration of the displacement. Severe prolonged toxicity is therefore not automatic.

Exam point: Correct rule: Protein-binding displacement is not automatically clinically severe or prolonged.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Protein-binding displacement is not automatically clinically severe or prolonged.
C. Low albumin may be important for interpretation of highly protein-bound medicines.
TRUEQuick reason: Total concentration may fall while the active free fraction differs.

Easy explanation: Laboratory total drug concentration includes both bound and free drug. In a patient with low albumin, the total concentration can appear low while the free active fraction is relatively higher than expected. This can make total concentration difficult to interpret for highly protein-bound drugs.

Exam point: Low albumin can make total concentration misleading for highly bound drugs.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Low albumin can make total concentration misleading for highly bound drugs.
D. A total plasma concentration does not always describe the pharmacologically active free concentration.
TRUEQuick reason: Binding changes can separate total and free concentrations.

Easy explanation: Total plasma concentration is the sum of bound and unbound drug, but pharmacological activity is more closely related to the free fraction for many drugs. If protein binding changes, a normal total concentration does not guarantee a normal free concentration.

Exam point: Total drug concentration and active free concentration are not always equivalent.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Total drug concentration and active free concentration are not always equivalent.
E. Plasma protein binding irreversibly destroys the drug.
FALSEQuick reason: Binding is usually reversible and acts as a dynamic reservoir.

Easy explanation: Plasma protein binding is usually reversible. Bound drug can dissociate back into the free pool as free drug distributes or is eliminated, so binding acts like a dynamic reservoir rather than permanently destroying the drug.

Exam point: Correct rule: Plasma protein binding is usually reversible and can act as a reservoir.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Plasma protein binding is usually reversible and can act as a reservoir.

18. Renal elimination

Big picture

  • Renal elimination involves glomerular filtration, active tubular secretion and tubular reabsorption.
  • Protein-bound drug is generally not freely filtered at the glomerulus; the free fraction is the main fraction available for filtration.
  • Renal impairment can reduce clearance and increase accumulation risk, while haemodialysis removal depends strongly on drug properties.
A. Only unbound drug is normally available for glomerular filtration.
TRUEQuick reason: The protein-drug complex is generally not filtered.

Easy explanation: At the glomerulus, large plasma proteins are generally retained in the blood. Drug molecules that are not protein-bound are therefore the main fraction available to pass into the filtrate. This is why protein binding can reduce glomerular filtration of a drug.

Exam point: Glomerular filtration mainly handles the unbound fraction.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Glomerular filtration mainly handles the unbound fraction.
B. Active tubular secretion occurs mainly in the proximal tubule.
TRUEQuick reason: Transport systems can secrete organic anions and cations.

Easy explanation: Active tubular secretion occurs mainly in the proximal tubule through transport systems for organic anions and cations. These transporters can move drug from blood into tubular fluid and can be an important part of renal clearance.

Exam point: Active secretion is mainly a proximal tubular transporter process.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Active secretion is mainly a proximal tubular transporter process.
C. Urine pH can influence reabsorption of some weak acids and weak bases.
TRUEQuick reason: Ionisation changes passive tubular reabsorption.

Easy explanation: Weak acids and weak bases change their degree of ionisation according to pH. The unionised form crosses lipid membranes more easily, so changing urine pH can alter passive tubular reabsorption and therefore renal excretion of some drugs.

Exam point: Urine pH affects ionisation and therefore passive tubular reabsorption of some weak acids/bases.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Urine pH affects ionisation and therefore passive tubular reabsorption of some weak acids/bases.
D. Renal impairment always increases renal drug clearance.
FALSEQuick reason: It commonly reduces renal clearance.

Easy explanation: Renal impairment commonly reduces processes such as glomerular filtration and sometimes tubular secretion. Therefore renal drug clearance usually falls rather than rises, increasing the risk of accumulation for drugs that depend on the kidneys for elimination.

Exam point: Correct rule: Renal impairment commonly reduces renal drug clearance.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Renal impairment commonly reduces renal drug clearance.
E. Haemodialysis removes every medicine equally well.
FALSEQuick reason: Removal depends on size, protein binding, Vd, water solubility and dialysis factors.

Easy explanation: Haemodialysis does not remove all medicines equally. Removal is usually better for small, water-soluble, poorly protein-bound drugs with a relatively low Vd, while highly protein-bound or extensively tissue-distributed drugs may be removed poorly.

Exam point: Correct rule: Dialysability depends on drug and dialysis characteristics; not all medicines are removed equally.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Dialysability depends on drug and dialysis characteristics; not all medicines are removed equally.

19. Routes and dosage forms

Big picture

  • IV administration places drug directly into systemic circulation and therefore bypasses the absorption step.
  • IM absorption can vary with local blood flow. Transdermal and inhaled routes can produce systemic as well as local effects when suitable.
  • Enteric coatings are designed to resist the stomach and release later in the intestine, not to dissolve rapidly in gastric acid.
A. Intravenous administration avoids the absorption step.
TRUEQuick reason: Drug is placed directly into systemic circulation.

Easy explanation: An IV dose is injected directly into systemic circulation. Because the drug does not have to cross a membrane to enter the blood, there is no absorption step and bioavailability is taken as 100% by definition.

Exam point: IV route bypasses absorption and first-pass presystemic loss.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: IV route bypasses absorption and first-pass presystemic loss.
B. Intramuscular absorption can be affected by local blood flow.
TRUEQuick reason: Poor perfusion may slow absorption.

Easy explanation: After an IM injection, drug must move from the muscle into the blood. Better local perfusion generally supports faster absorption, while shock, poor circulation or differences in the injection site can slow or make absorption more variable.

Exam point: IM absorption depends partly on local blood flow/perfusion.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: IM absorption depends partly on local blood flow/perfusion.
C. Transdermal systems can provide sustained systemic delivery for suitable drugs.
TRUEQuick reason: They release drug across skin over time.

Easy explanation: A transdermal patch can release a suitable drug across the skin gradually for many hours or even days, producing sustained systemic delivery. However, not every drug is suitable because skin is an effective barrier and only certain drug properties allow adequate penetration.

Exam point: Transdermal systems can provide prolonged systemic delivery for appropriately selected drugs.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Transdermal systems can provide prolonged systemic delivery for appropriately selected drugs.
D. Inhaled medicines can produce only local effects.
FALSEQuick reason: Some inhaled medicines are systemically absorbed, and inhalation can also be used for systemic delivery.

Easy explanation: Inhaled medicines are often used for local effects in the airways, but some of the inhaled dose can enter systemic circulation. Inhalation can also be used intentionally for systemic effects. Therefore inhaled drugs are not limited to local action only.

Exam point: Correct rule: Inhaled drugs may have local and/or systemic effects.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Inhaled drugs may have local and/or systemic effects.
E. An enteric coating is designed to dissolve rapidly in the stomach.
FALSEQuick reason: It is designed to resist gastric conditions and release later in the intestine.

Easy explanation: An enteric coating is designed to resist the acidic environment of the stomach. It remains intact during gastric transit and dissolves later when it reaches the higher-pH environment of the intestine. This can protect the drug from acid or protect the stomach from the drug.

Exam point: Correct rule: Enteric coating resists the stomach and releases later in the intestine.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Enteric coating resists the stomach and releases later in the intestine.

20. Core medicine-safety checks

Big picture

  • Medicine-safety checks such as allergy review, duplicate therapy checks, dose/formulation checks and interaction review reduce preventable harm.
  • Crushing modified-release products can destroy release control and may cause dose dumping or loss of prolonged action.
  • Medication reconciliation helps detect omissions, duplications and discrepancies when patients move between care settings or medicine lists change.
A. Allergy status should be checked before supplying a newly prescribed medicine.
TRUEQuick reason: This can prevent avoidable re-exposure.

Easy explanation: Before supplying a new prescription, checking allergy status can prevent accidental re-exposure to a medicine that previously caused a serious reaction. The specific drug, the type of reaction and related medicines may all be important for safe dispensing.

Exam point: Check allergy status before supply, especially for a new prescription.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Check allergy status before supply, especially for a new prescription.
B. Duplicate therapy can increase adverse-effect risk.
TRUEQuick reason: Different brand names or combination products can conceal duplication.

Easy explanation: Duplicate therapy can be hidden when the same active ingredient appears under different brand names or inside combination products. Unnecessary duplication can increase the total dose and the risk of adverse effects, so active ingredients and therapeutic classes should be reviewed.

Exam point: Check for duplicate active ingredients and unnecessary therapeutic duplication.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Check for duplicate active ingredients and unnecessary therapeutic duplication.
C. A serious unexpected suspected adverse reaction should be handled through the applicable local reporting pathway.
TRUEQuick reason: Pharmacovigilance supports detection and prevention of medicine harm.

Easy explanation: Pharmacovigilance systems are designed to detect and reduce medicine-related harm. A serious or unexpected suspected ADR should be managed and reported through the applicable local pathway. The word suspected is important because absolute proof is not always required before reporting a safety concern.

Exam point: Serious unexpected suspected ADRs should follow the applicable pharmacovigilance reporting pathway.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Serious unexpected suspected ADRs should follow the applicable pharmacovigilance reporting pathway.
D. All modified-release tablets should be crushed before administration.
FALSEQuick reason: Crushing may destroy release control and cause dose dumping; product-specific instructions must be checked.

Easy explanation: Modified-release tablets are designed to release drug at a controlled rate. Crushing can destroy that control, causing rapid release or dose dumping, higher toxicity risk, or a shorter duration of action. Always check the specific product information before crushing or altering the dosage form.

Exam point: Correct rule: Do not crush modified-release products unless the specific product information confirms it is safe.
Check yourself: First identify what is wrong in the statement. Then say the corrected rule without looking: Correct rule: Do not crush modified-release products unless the specific product information confirms it is safe.
E. Medication reconciliation helps identify omissions, duplications and interactions.
TRUEQuick reason: Comparing the complete medicine list across transitions reduces preventable discrepancies.

Easy explanation: Medication reconciliation compares the patient's complete medicine list with new orders when care changes, such as admission, transfer or discharge. This process can identify omitted medicines, duplicate therapy, wrong doses and clinically important interactions or discrepancies.

Exam point: Medication reconciliation reduces discrepancies when care settings or medicine lists change.
Check yourself: Explain in one sentence why this statement is TRUE. Then say the core rule without looking: Medication reconciliation reduces discrepancies when care settings or medicine lists change.

Quick Revision Answer Key

Use this only for self-checking. Try all statements before looking at the answer key.

01. Bioavailability and exposure - TTFTF

02. Factors affecting absorption - TFTFT

03. First-pass effect - TFTTF

04. Volume of distribution - TFFTT

05. Clearance - TTFTT

06. Elimination half-life - TTTFT

07. Steady state and accumulation - TFTFT

08. Loading dose - TFTTF

09. Maintenance dosing - TTFTT

10. First-order elimination - TTTFT

11. Zero-order and capacity-limited elimination - TTFTT

12. Agonists and antagonists - TTFTT

13. Potency and efficacy - TTFTF

14. Therapeutic index and monitoring - TTTFT

15. Adverse drug reactions - TTFTF

16. Drug interactions - TTTFT

17. Protein binding and free drug - TFTTF

18. Renal elimination - TTTFF

19. Routes and dosage forms - TTTFF

20. Core medicine-safety checks - TTTFT

Final revision method

Round 1: Attempt all 100 statements as TRUE/FALSE. Round 2: Review only the statements you got wrong and read the full explanation. Round 3: Cover the Exam point box and say the correct rule aloud in your own words.

Last modified: Sunday, 6 September 2026, 3:36 AM