Introduction: The excretion of drugs is a vital component of pharmacokinetics and drug elimination that B.Pharm students must master. This topic covers renal excretion (glomerular filtration, tubular secretion and reabsorption, urine pH effects, ion trapping), biliary and fecal clearance, pulmonary and mammary routes, and the influence of drug properties (lipophilicity, molecular size, protein binding, pKa) and transporters (OAT, OCT, MRP) on elimination. Clinical considerations include enterohepatic recycling, dialysis removal, and dose adjustments in renal or hepatic impairment. Understanding clearance, half-life, and fraction excreted unchanged helps optimize therapy and avoid toxicity. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which of the following are recognized routes for drug excretion?
- Renal excretion
- Biliary excretion
- Pulmonary excretion
- All of the above
Correct Answer: All of the above
Q2. Which statement best describes glomerular filtration of drugs?
- Only protein-bound drug is filtered through the glomerulus
- Both bound and unbound drug are filtered equally
- Only unbound (free) drug is subject to glomerular filtration
- Filtration is the predominant route for very large protein-bound drugs
Correct Answer: Only unbound (free) drug is subject to glomerular filtration
Q3. Organic anion transporters (OATs) and organic cation transporters (OCTs) in the kidney primarily mediate which process?
- Glomerular filtration
- Passive tubular reabsorption
- Active tubular secretion
- Biliary excretion
Correct Answer: Active tubular secretion
Q4. Ion trapping in the urine results in increased excretion of which type of drug when urine is acidified?
- Weak acids
- Weak bases
- Neutral non-ionizable drugs
- Highly protein-bound drugs
Correct Answer: Weak bases
Q5. Which physicochemical properties favor biliary excretion of a drug?
- Low molecular weight and nonpolar
- High molecular weight and polar conjugates
- High lipophilicity and neutral charge
- Extensive plasma protein binding
Correct Answer: High molecular weight and polar conjugates
Q6. Enterohepatic recycling of a drug typically causes which pharmacokinetic effect?
- Reduced oral bioavailability
- Shorter elimination half-life
- Prolonged plasma half-life and secondary concentration peaks
- Complete renal excretion of parent drug
Correct Answer: Prolonged plasma half-life and secondary concentration peaks
Q7. Pulmonary excretion is most important for elimination of which class of agents?
- Highly ionized antibiotics
- Volatile anesthetic gases
- Large peptide drugs
- Conjugated glucuronides
Correct Answer: Volatile anesthetic gases
Q8. A renal clearance value greater than the glomerular filtration rate (GFR) for a drug indicates which process?
- Purely passive reabsorption
- No renal handling of the drug
- Net tubular secretion in addition to filtration
- Extensive protein binding preventing filtration
Correct Answer: Net tubular secretion in addition to filtration
Q9. High plasma protein binding of a drug generally leads to which effect on renal excretion?
- Increased glomerular filtration
- Reduced filtration and lower renal clearance
- Enhanced tubular secretion
- Unchanged renal elimination
Correct Answer: Reduced filtration and lower renal clearance
Q10. Phase II conjugation reactions (e.g., glucuronidation) usually affect drug excretion by:
- Decreasing water solubility and reducing elimination
- Increasing lipophilicity and promoting tissue uptake
- Increasing polarity and facilitating renal or biliary excretion
- Preventing drug metabolism in the liver
Correct Answer: Increasing polarity and facilitating renal or biliary excretion
Q11. Which equation correctly relates elimination half-life (t1/2), volume of distribution (Vd), and clearance (CL)?
- t1/2 = CL × Vd
- t1/2 = 0.693 × Vd / CL
- t1/2 = 0.693 × CL / Vd
- t1/2 = Vd / (0.693 × CL)
Correct Answer: t1/2 = 0.693 × Vd / CL
Q12. Dose adjustment in renal impairment is most reliably guided by which clinical measure?
- Serum albumin concentration
- Estimated creatinine clearance or GFR
- ALT and AST levels
- Serum potassium concentration
Correct Answer: Estimated creatinine clearance or GFR
Q13. Which drug characteristics predict efficient removal by hemodialysis?
- High volume of distribution and high protein binding
- Low volume of distribution and low protein binding
- Extensive tissue binding and large molecular size
- Highly lipophilic and heavily protein-bound
Correct Answer: Low volume of distribution and low protein binding
Q14. Which transporter family is primarily implicated in renal tubular secretion of organic anions?
- OCT (organic cation transporter)
- OAT (organic anion transporter)
- P-glycoprotein (P-gp)
- BSEP (bile salt export pump)
Correct Answer: OAT (organic anion transporter)
Q15. Alkalinization of urine will have which effect on excretion of aspirin (a weak acid)?
- Decrease aspirin excretion
- Increase aspirin excretion
- No effect on aspirin excretion
- Convert aspirin to a weak base
Correct Answer: Increase aspirin excretion
Q16. Why do neonates often exhibit reduced drug excretion compared with adults?
- Higher renal blood flow and excessive GFR
- Immature hepatic conjugation and lower renal tubular function
- Increased expression of transporters like OAT and OCT
- Enhanced pulmonary elimination mechanisms
Correct Answer: Immature hepatic conjugation and lower renal tubular function
Q17. Which property makes a drug more likely to be secreted into breast milk?
- Very high plasma protein binding (>99%)
- Highly ionized strong acids
- Lipophilicity and being a weak base with pKa favoring ionization in milk
- Extensive hepatic extraction with no parent drug in plasma
Correct Answer: Lipophilicity and being a weak base with pKa favoring ionization in milk
Q18. The fraction excreted unchanged in urine (fe) refers to:
- The proportion of a dose eliminated as metabolites in feces
- The fraction of administered dose excreted in urine as unchanged parent drug
- The ratio of renal clearance to hepatic clearance
- Percentage of drug bound to plasma proteins
Correct Answer: The fraction of administered dose excreted in urine as unchanged parent drug
Q19. Which clearance method is considered the gold standard for measuring glomerular filtration rate (GFR)?
- Creatinine clearance
- Inulin clearance
- Urinary urea clearance
- Para-aminohippuric acid (PAH) clearance
Correct Answer: Inulin clearance
Q20. Cholestasis primarily affects drug elimination by reducing which route?
- Renal glomerular filtration
- Biliary excretion
- Pulmonary elimination
- Renal tubular secretion
Correct Answer: Biliary excretion
Q21. Formation of glucuronide conjugates commonly enhances which excretory pathway?
- Pulmonary exhalation of parent drug
- Biliary and renal elimination of polar conjugates
- Increased reabsorption in renal tubules
- Accumulation within adipose tissue
Correct Answer: Biliary and renal elimination of polar conjugates
Q22. Active tubular secretion in the kidney is characterized by which features?
- Energy-independent passive diffusion
- Carrier-mediated, saturable, and energy-dependent transport
- Nonselective filtration of protein-bound drug
- Unchanged by competitive inhibitors
Correct Answer: Carrier-mediated, saturable, and energy-dependent transport
Q23. Which drug property most favors pulmonary elimination into expired air?
- High blood solubility and large molecular size
- High volatility and low blood solubility
- Extensive conjugation to polar metabolites
- Strong plasma protein binding
Correct Answer: High volatility and low blood solubility
Q24. For a drug that is filtered but neither secreted nor reabsorbed, renal clearance equals:
- Total plasma clearance
- Zero
- GFR multiplied by the free (unbound) fraction
- GFR plus tubular secretion rate
Correct Answer: GFR multiplied by the free (unbound) fraction
Q25. A classic pharmacokinetic consequence of enterohepatic recycling is:
- Elimination half-life reduction
- Complete prevention of biliary excretion
- Occurrence of secondary plasma concentration peaks
- Immediate renal clearance of conjugates
Correct Answer: Occurrence of secondary plasma concentration peaks
Q26. In patients with significant renal impairment, what generally happens to the half-life of a primarily renally-excreted drug?
- Half-life decreases
- Half-life remains unchanged
- Half-life increases
- Drug becomes entirely metabolized hepatically
Correct Answer: Half-life increases
Q27. Which formula defines total body clearance using AUC after an IV bolus dose?
- CL = AUC / Dose
- CL = Dose × AUC
- CL = Dose / AUC
- CL = Vd × t1/2
Correct Answer: CL = Dose / AUC
Q28. Which of the following will NOT increase renal excretion of a weak acid drug?
- Alkalinization of urine
- Increasing urine flow rate
- Acidification of urine
- Reducing tubular reabsorption
Correct Answer: Acidification of urine
Q29. Salivary drug concentrations are most useful clinically because they:
- Reflect total (bound + unbound) plasma drug concentration
- Indicate hepatic clearance directly
- Reflect the free (unbound) drug concentration and are affected by pH partitioning
- Provide a measure of biliary excretion
Correct Answer: Reflect the free (unbound) drug concentration and are affected by pH partitioning
Q30. Which transporter is commonly involved in canalicular (biliary) excretion of glucuronide conjugates?
- P-glycoprotein (P-gp/ABCB1)
- MRP2 (ABCC2)
- OCT2
- GLUT2
Correct Answer: MRP2 (ABCC2)
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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