COMPREHENSIVE BASIC PHARMACOLOGY - 120 OmpathStudy

COMPREHENSIVE BASIC PHARMACOLOGY - 120 CHALLENGING MCQs --- SECTION A: PHARMACOKINETICS (25 Questions) 1. Bioavailability is BEST defined as: A) Rate of drug absorption B) Fraction of unchanged drug reaching systemic circulation C) Drug concentration at receptor sites D) Degree of protein binding Answer: B Bioavailability (F) is the percentage of administered drug that reaches systemic circulation unchanged. IV route has 100% bioavailability by definition. 2. A drug that undergoes extensive first-pass metabolism will show: A) Increased oral bioavailability B) Reduced oral bioavailability C) No effect on bioavailability D) Increased half-life Answer: B First-pass metabolism in the liver reduces the amount of drug reaching systemic circulation, decreasing oral bioavailability. Examples include nitroglycerin and propranolol. 3. A patient with hepatic cirrhosis requires a drug with high first-pass metabolism. Which pharmacokinetic parameter change would you most expect? A) Decreased bioavailability B) Increased bioavailability C) No change in bioavailability D) Decreased volume of distribution Answer: B Hepatic cirrhosis reduces first-pass metabolism, so less drug is metabolized before reaching systemic circulation, resulting in increased bioavailability and risk of toxicity. 4. Volume of distribution (Vd) increases when a drug is: A) Highly protein-bound B) Highly water soluble C) Highly lipid soluble D) Administered intravenously Answer: C Lipid-soluble drugs penetrate cell membranes easily and distribute widely into tissues, resulting in large Vd values. 5. A drug has a volume of distribution (Vd) of 400L in a 70kg patient. What does this indicate? A) Drug is confined to plasma B) Drug is confined to extracellular fluid C) Drug is highly tissue-bound D) Drug has poor absorption Answer: C A Vd of 400L (much larger than total body water ~42L) indicates the drug is extensively distributed and bound to tissues outside the vascular compartment. 6. Clearance is defined as: A) Fraction metabolized per hour B) Volume of plasma cleared of drug per unit time C) Rate of drug absorption D) Protein binding capacity Answer: B Clearance (CL) represents the volume of plasma from which drug is completely removed per unit time (mL/min or L/hr), reflecting elimination efficiency. 7. The major determinant of half-life (t½) is: A) Bioavailability B) Clearance and Vd C) Protein binding only D) Route of administration Answer: B Half-life = (0.693 × Vd) / CL. It depends on both volume of distribution and clearance. Changes in either parameter affect t½. 8. If a drug's half-life is 6 hours, approximately how long will it take to reach 97% steady-state concentration with continuous dosing? A) 12 hours B) 18 hours C) 24 hours D) 30 hours Answer: D Steady state is reached after approximately 5 half-lives (5 × 6 = 30 hours), which achieves about 97% of the final steady-state concentration. 9. Zero-order kinetics means: A) A constant fraction is eliminated B) A constant amount is eliminated C) Elimination is concentration dependent D) Drug never reaches steady state Answer: B In zero-order kinetics, a fixed amount (not fraction) of drug is eliminated per unit time, regardless of concentration. Occurs with enzyme saturation (e.g., high-dose aspirin, alcohol, phenytoin). 10. Which statement about zero-order kinetics is TRUE? A) A constant fraction of drug is eliminated per unit time B) Half-life remains constant regardless of dose C) Elimination rate is independent of drug concentration D) Doubling the dose doubles the time to eliminate the drug Answer: C In zero-order kinetics, a constant AMOUNT (not fraction) is eliminated per unit time, regardless of concentration. This occurs when elimination mechanisms are saturated. 11. Steady-state concentration in continuous infusion mainly depends on: A) Loading dose B) Half-life C) Clearance D) Route of administration Answer: C Steady-state concentration (Css) = Infusion rate / Clearance. It's determined by the balance between input rate and elimination (clearance), not by Vd or t½. 12. A loading dose is required to: A) Maintain steady state B) Rapidly achieve therapeutic concentration C) Reduce toxicity D) Increase bioavailability Answer: B Loading doses rapidly achieve therapeutic concentrations without waiting 5 half-lives. Loading dose = (Vd × Target concentration) / Bioavailability. 13. A drug is 95% protein-bound. In a patient with hypoalbuminemia, what is the most likely consequence? A) Decreased total drug concentration, increased free drug concentration B) Increased total drug concentration, decreased free drug concentration C) Both total and free drug concentrations decrease D) Decreased total drug concentration, unchanged free drug concentration Answer: D With less protein available for binding, total drug decreases, but the body maintains free (active) drug concentration through homeostatic mechanisms and increased clearance. 14. Which organ is MOST responsible for Phase I metabolism?