Introduction and definition of Pharmacokinetics MCQs With Answer

Pharmacokinetics studies the time course of drugs in the body — absorption, distribution, metabolism and excretion (ADME). For B.Pharm students, mastering pharmacokinetics is essential to predict drug concentration, dose regimen, bioavailability, clearance, half-life and volume of distribution. This curated set of MCQs covers compartmental and non-compartmental models, first-order versus zero-order kinetics, hepatic and renal elimination, bioequivalence, protein binding, enzyme induction and inhibition, and factors altering kinetics. Problems include calculation of half-life, clearance, AUC, and interpretation of concentration–time curves to build numerical and clinical reasoning skills required in pharmacotherapy and drug development. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What does ADME stand for in pharmacokinetics?

• Absorption, Distribution, Metabolism, Excretion
• Absorption, Diffusion, Metabolism, Elimination
• Administration, Distribution, Metabolism, Elimination
• Adsorption, Distribution, Modification, Excretion

Correct Answer: Absorption, Distribution, Metabolism, Excretion

Q2. Which parameter best describes the proportionality between dose and plasma AUC after an IV bolus?

• Volume of distribution (Vd)
• Clearance (CL)
• Half-life (t1/2)
• Bioavailability (F)

Correct Answer: Clearance (CL)

Q3. The formula t1/2 = 0.693/ke relates half-life to which rate constant?

• Absorption rate constant (ka)
• Elimination rate constant (ke)
• Distribution rate constant (kd)
• Metabolism rate constant (km)

Correct Answer: Elimination rate constant (ke)

Q4. For a drug eliminated by first-order kinetics, how does the percentage of drug eliminated per unit time behave?

• Constant amount is eliminated each hour
• Constant percentage is eliminated each hour
• Elimination is independent of concentration
• Elimination increases with time

Correct Answer: Constant percentage is eliminated each hour

Q5. Which equation gives steady-state concentration (Css) during a constant IV infusion?

• Css = Dose / Vd
• Css = Rate of infusion (R0) / Clearance (CL)
• Css = 0.693 / t1/2
• Css = AUC × CL

Correct Answer: Css = Rate of infusion (R0) / Clearance (CL)

Q6. How many half-lives approximately are required to reach >95% of steady state for a drug given by repeated dosing?

• 1 half-life
• 2 half-lives
• 4–5 half-lives
• 10 half-lives

Correct Answer: 4–5 half-lives

Q7. Which expression correctly defines apparent volume of distribution (Vd)?

• Vd = Dose / C0 (for IV bolus)
• Vd = CL / ke
• Vd = AUC / Dose
• Vd = Css × CL

Correct Answer: Vd = Dose / C0 (for IV bolus)

Q8. If clearance (CL) is 10 L/h and Vd is 50 L, what is the elimination half-life (t1/2)?

• 0.693 × (50/10) = 3.47 h
• 0.693 × (10/50) = 0.139 h
• 0.693 × (50 × 10) = 346.5 h
• 0.693 / (50/10) = 0.139 h

Correct Answer: 0.693 × (50/10) = 3.47 h

Q9. Oral bioavailability (F) is reduced primarily by which process?

• Renal excretion
• First-pass metabolism in liver/intestine
• Plasma protein binding
• Volume of distribution

Correct Answer: First-pass metabolism in liver/intestine

Q10. The AUC after an intravenous dose is directly proportional to:

• Dose / Clearance
• Clearance / Dose
• Vd × ke
• Ka / Vd

Correct Answer: Dose / Clearance

Q11. Which situation most closely indicates a high volume of distribution (Vd)?

• Drug largely confined to plasma bound to albumin
• Drug extensively bound to tissue and distributed widely
• Drug eliminated solely by renal filtration
• Drug remains in GI lumen without absorption

Correct Answer: Drug extensively bound to tissue and distributed widely

Q12. A drug follows Michaelis–Menten (capacity-limited) kinetics. Which statement is true when dose approaches Km?

• Elimination rate becomes constant and independent of concentration
• Elimination rate becomes proportional to concentration (first-order)
• Small changes in dose can produce disproportionate plasma concentration changes
• Bioavailability increases linearly with dose

Correct Answer: Small changes in dose can produce disproportionate plasma concentration changes

Q13. Which of the following drugs is a classic example of capacity-limited (non-linear) kinetics?

• Penicillin
• Digoxin
• Phenytoin
• Metformin

Correct Answer: Phenytoin

Q14. The extraction ratio (E) of a drug is defined as:

• E = CL / Vd
• E = (Cin – Cout) / Cin for an eliminating organ
• E = AUCpo / AUCiv
• E = Dose × F / CL

Correct Answer: E = (Cin – Cout) / Cin for an eliminating organ

Q15. For a drug cleared only by glomerular filtration, renal clearance (CLr) equals:

• GFR × fraction unbound (fu)
• GFR / fu
• fu × Vd
• GFR × Vd

Correct Answer: GFR × fraction unbound (fu)

Q16. Loading dose (LD) to rapidly achieve target concentration is calculated as:

• LD = Css × CL
• LD = Css × Vd
• LD = CL / Css
• LD = Vd / Css

Correct Answer: LD = Css × Vd

Q17. Which parameter is independent of dose and reflects body’s ability to eliminate a drug?

• Area under the concentration–time curve (AUC)
• Clearance (CL)
• Maximum concentration (Cmax)
• Time to peak (Tmax)

Correct Answer: Clearance (CL)

Q18. Bioequivalence between two formulations requires the 90% confidence interval for Cmax and AUC to fall within:

• 50–150%
• 70–130%
• 80–125%
• 90–110%

Correct Answer: 80–125%

Q19. Which process primarily increases the free (unbound) fraction of a highly protein-bound drug and may increase clearance?

• Co-administration of a drug that displaces it from plasma proteins
• Decrease in hepatic blood flow
• Administration with fatty meals
• Slow gastric emptying

Correct Answer: Co-administration of a drug that displaces it from plasma proteins

Q20. For an IV bolus, which expression gives concentration at time t (Ct) in a one-compartment, first-order elimination model?

• Ct = C0 × e^(−ke t)
• Ct = C0 × (1 − e^(−ke t))
• Ct = Dose / (Vd × ke)
• Ct = AUC / CL

Correct Answer: Ct = C0 × e^(−ke t)

Q21. When hepatic clearance is flow-limited, which factor most strongly determines clearance?

• Intrinsic hepatic metabolic capacity only
• Fraction unbound only
• Hepatic blood flow
• Volume of distribution

Correct Answer: Hepatic blood flow

Q22. AUC after oral dosing is 50 mg·h/L and the oral dose was 100 mg. If clearance is 2 L/h, what is the bioavailability (F)? (Use AUC = Dose × F / CL)

• F = (50 × 2) / 100 = 1.0 (100%)
• F = (100 × 2) / 50 = 4.0 (400%)
• F = (50 × 100) / 2 = 2500%
• F = 50 / (100 × 2) = 0.25 (25%)

Correct Answer: F = (50 × 2) / 100 = 1.0 (100%)

Q23. Mean residence time (MRT) for a drug is conceptually:

• The average time a molecule spends in the body after dosing
• The time to reach maximum concentration
• The time for half the dose to be absorbed
• The lag time before absorption starts

Correct Answer: The average time a molecule spends in the body after dosing

Q24. Enterohepatic recycling typically causes which effect on plasma concentration–time profile?

• Single sharp peak with rapid decline
• Multiple peaks or secondary rises in concentration
• Complete prevention of absorption
• Immediate elimination without distribution

Correct Answer: Multiple peaks or secondary rises in concentration

Q25. Which metric best quantifies total systemic exposure to a drug?

• Cmax
• Tmax
• AUC (area under the concentration–time curve)
• Vd

Correct Answer: AUC (area under the concentration–time curve)

Q26. When two drugs are cleared by the same hepatic enzyme, co-administration that inhibits the enzyme will most likely:

• Decrease plasma concentration of the victim drug
• Increase plasma concentration and half-life of the victim drug
• Have no effect on pharmacokinetics
• Increase renal clearance of the victim drug

Correct Answer: Increase plasma concentration and half-life of the victim drug

Q27. Which statement about first-pass metabolism is correct?

• It increases oral bioavailability
• It occurs mainly after IV administration
• It may significantly reduce systemic availability of some orally administered drugs
• It is independent of intestinal and hepatic enzymes

Correct Answer: It may significantly reduce systemic availability of some orally administered drugs

Q28. For non-compartmental analysis, clearance can be calculated as:

• CL = Dose / AUC
• CL = AUC / Dose
• CL = Vd × ke
• CL = Dose × Vd

Correct Answer: CL = Dose / AUC

Q29. A drug has a half-life of 8 hours. After how many hours will its plasma concentration be approximately 12.5% of the initial concentration following first-order elimination?

• 8 hours
• 16 hours
• 24 hours
• 32 hours

Correct Answer: 24 hours

Q30. The primary effect of increased plasma protein binding on total drug concentration and free concentration is:

• Total concentration decreases, free concentration unchanged
• Total concentration increases, free concentration may remain similar initially
• Both total and free concentrations decrease proportionally
• Free concentration increases while total concentration decreases

Correct Answer: Total concentration increases, free concentration may remain similar initially

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