Understanding kinetics of drug elimination is essential for safe and effective dosing in B.Pharm programs. This concise introduction covers core concepts—half-life (t1/2), clearance (CL), volume of distribution (Vd), elimination rate constant (ke), first-order and zero-order kinetics, renal and hepatic excretion, metabolic pathways, and steady-state principles—so students can analyze pharmacokinetic profiles, calculate dosing regimens, and predict drug accumulation. Emphasis on equations, units, linear vs nonlinear elimination, extraction ratio, and compartment models prepares learners for clinical and industry applications. Practice with focused MCQs reinforces problem solving and numerical skills required for pharmaceutics, therapeutics, and regulatory exams. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the pharmacokinetic definition of half-life (t1/2)?
- The time required for 50% of the administered dose to be excreted unchanged
- The time required for the plasma drug concentration to decrease by 50%
- The time by which drug metabolism is complete
- The time required to reach steady state
Correct Answer: The time required for the plasma drug concentration to decrease by 50%
Q2. Which equation correctly relates half-life (t1/2) to the elimination rate constant (ke) for first-order kinetics?
- t1/2 = ke / 0.693
- t1/2 = 0.693 / ke
- t1/2 = CL / Vd
- t1/2 = Vd × CL
Correct Answer: t1/2 = 0.693 / ke
Q3. Which expression defines total body clearance (CL) in terms of elimination rate constant and volume of distribution?
- CL = ke / Vd
- CL = Vd / ke
- CL = ke × Vd
- CL = t1/2 × Vd
Correct Answer: CL = ke × Vd
Q4. What are the typical units for systemic clearance used in clinical pharmacokinetics?
- mg/L
- mL/min or L/hr
- mol/L
- minutes per liter
Correct Answer: mL/min or L/hr
Q5. Which statement best describes first-order elimination kinetics?
- The elimination rate is constant regardless of concentration
- The elimination rate is proportional to the drug concentration
- Clearance decreases with increasing dose due to saturation
- Half-life varies directly with dose
Correct Answer: The elimination rate is proportional to the drug concentration
Q6. Which characteristic defines zero-order elimination?
- Rate of elimination proportional to concentration
- Rate of elimination is constant (independent of concentration)
- Clearance increases with concentration
- Half-life decreases as concentration falls
Correct Answer: Rate of elimination is constant (independent of concentration)
Q7. If clearance doubles while volume of distribution remains unchanged, what happens to the half-life?
- Half-life doubles
- Half-life remains unchanged
- Half-life halves
- Half-life increases tenfold
Correct Answer: Half-life halves
Q8. Approximately how many half-lives are required to reach steady state with repeated dosing for a first-order drug?
- 1 half-life
- 2 half-lives
- 4–5 half-lives
- 10–12 half-lives
Correct Answer: 4–5 half-lives
Q9. Which change will increase accumulation during multiple dosing?
- Increasing the dosing interval relative to t1/2
- Decreasing the dosing interval relative to t1/2
- Decreasing dose while keeping interval constant
- Switching from iv to oral with same bioavailability
Correct Answer: Decreasing the dosing interval relative to t1/2
Q10. Renal clearance greater than GFR for a drug suggests which process is occurring?
- Only glomerular filtration
- Net tubular secretion
- Complete reabsorption
- No renal involvement
Correct Answer: Net tubular secretion
Q11. A drug with a high hepatic extraction ratio (ER) is most likely limited by which parameter?
- Hepatic enzyme capacity only
- Liver blood flow (flow-limited clearance)
- Renal excretion
- Protein binding in plasma
Correct Answer: Liver blood flow (flow-limited clearance)
Q12. How is extraction ratio (ER) defined for an organ such as the liver?
- ER = (Cv – Ca)/Ca
- ER = (Ca – Cv)/Ca
- ER = CL / Vd
- ER = fu × GFR
Correct Answer: ER = (Ca – Cv)/Ca
Q13. Which description best fits Michaelis–Menten (saturable) elimination?
- Elimination rate always proportional to concentration
- At high concentrations, elimination rate approaches a maximum Vmax independent of concentration
- Clearance is constant regardless of dose
- Half-life decreases linearly with dose
Correct Answer: At high concentrations, elimination rate approaches a maximum Vmax independent of concentration
Q14. In nonlinear (capacity-limited) kinetics, what happens when dose is increased near enzyme saturation?
- Plasma concentrations increase proportionally to dose
- Clearance increases proportionally to dose
- Plasma concentrations may increase disproportionately more than dose
- Half-life decreases predictably
Correct Answer: Plasma concentrations may increase disproportionately more than dose
Q15. Which pattern is characteristic of a two-compartment model after IV bolus?
- Single exponential decline with no distribution phase
- Initial rapid distribution phase followed by slower elimination phase
- Zero-order elimination only
- Immediate attainment of steady state
Correct Answer: Initial rapid distribution phase followed by slower elimination phase
Q16. A drug with Vd much larger than total body water most likely indicates what?
- Drug confined to plasma
- High tissue binding or partitioning into tissues
- Drug eliminated only by kidneys
- Drug is highly hydrophilic
Correct Answer: High tissue binding or partitioning into tissues
Q17. How is total body clearance related to individual organ clearances?
- Total clearance is the product of renal and hepatic clearance
- Total clearance equals the sum of renal, hepatic and other organ clearances
- Total clearance equals Vd × t1/2
- Total clearance is always equal to hepatic clearance
Correct Answer: Total clearance equals the sum of renal, hepatic and other organ clearances
Q18. For a first-order drug, which property remains constant over time?
- Amount eliminated per unit time
- Fraction (percentage) of drug eliminated per unit time
- Absolute change in concentration per unit time
- Dose independent AUC
Correct Answer: Fraction (percentage) of drug eliminated per unit time
Q19. If ke = 0.1 hr⁻¹, what is the approximate half-life?
- 0.693 hours
- 6.93 hours
- 10 hours
- 69.3 hours
Correct Answer: 6.93 hours
Q20. If Vd = 70 L and CL = 7 L/hr, what is the elimination rate constant ke?
- 0.01 hr⁻¹
- 0.1 hr⁻¹
- 1.0 hr⁻¹
- 10 hr⁻¹
Correct Answer: 0.1 hr⁻¹
Q21. Which formula gives the intravenous loading dose required to immediately achieve a target steady-state concentration (Css)?
- Loading dose = Css × CL
- Loading dose = Css × Vd / F
- Loading dose = CL / (Css × F)
- Loading dose = t1/2 × Vd
Correct Answer: Loading dose = Css × Vd / F
Q22. Which formula gives the maintenance dose rate (input rate) to maintain a target Css?
- Maintenance rate = CL × Css / F
- Maintenance rate = Vd × Css
- Maintenance rate = t1/2 × Css
- Maintenance rate = Css / ke
Correct Answer: Maintenance rate = CL × Css / F
Q23. Bioavailability (F) primarily affects which pharmacokinetic parameter derived from oral dosing?
- Volume of distribution (Vd)
- Elimination half-life (t1/2)
- Area under the plasma concentration–time curve (AUC)
- Intrinsic hepatic clearance (CLint)
Correct Answer: Area under the plasma concentration–time curve (AUC)
Q24. For a highly protein-bound drug, which statement about elimination is correct?
- Total drug (bound + unbound) is eliminated at the same rate as free drug
- Only the unbound (free) fraction is available for glomerular filtration and hepatic clearance
- Protein binding increases renal filtration clearance directly
- Protein binding has no effect on distribution
Correct Answer: Only the unbound (free) fraction is available for glomerular filtration and hepatic clearance
Q25. For a drug that is filtered but neither secreted nor reabsorbed, renal clearance (CLr) approximates which expression?
- CLr = GFR
- CLr = fu × GFR
- CLr = Vd × GFR
- CLr = CLtotal / fu
Correct Answer: CLr = fu × GFR
Q26. Hepatic clearance (CLh) under the well-stirred model can be calculated by which expression?
- CLh = Qh × ER
- CLh = Vd / Qh
- CLh = ke × t1/2
- CLh = fu × GFR
Correct Answer: CLh = Qh × ER
Q27. Approximately how many half-lives are required to reach 90% of steady state for a first-order drug?
- 1 half-life
- 2 half-lives
- 3.3 half-lives
- 8 half-lives
Correct Answer: 3.3 half-lives
Q28. Which drug properties make a compound most likely to be effectively removed by hemodialysis?
- High Vd and high protein binding
- Low Vd and low protein binding
- High lipophilicity and high Vd
- High molecular weight and high protein binding
Correct Answer: Low Vd and low protein binding
Q29. Convert clearance of 7 L/hr to mL/min. Which is correct?
- 1.17 mL/min
- 11.67 mL/min
- 116.67 mL/min
- 7000 mL/min
Correct Answer: 116.67 mL/min
Q30. In linear (dose-independent) pharmacokinetics, which parameter remains unchanged when the dose is increased within the linear range?
- Clearance (CL)
- Area under the curve (AUC)
- Steady-state concentration (Css) for the same dosing regimen
- Elimination half-life always changes
Correct Answer: Clearance (CL)
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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