SPEX SPEX Pharmacology 2 — Questions and Answers
Question 1: Which medication requires routine monitoring of serum drug levels due to its narrow therapeutic index?
- Amoxicillin
- Lithium (Correct answer)
- Metformin
- Atorvastatin
Correct answer: Lithium
Lithium has a narrow therapeutic index, requiring regular serum level monitoring to prevent toxicity.
Question 2: A patient develops 'red man syndrome' during IV infusion. Which drug is responsible?
- Penicillin G
- Vancomycin (Correct answer)
- Ceftriaxone
- Azithromycin
Correct answer: Vancomycin
Vancomycin infused too rapidly causes non-immune mast cell degranulation, leading to flushing and erythema known as red man syndrome.
Question 3: Which antihypertensive is contraindicated in bilateral renal artery stenosis?
- Amlodipine
- Hydrochlorothiazide
- ACE inhibitors (Correct answer)
- Beta-blockers
Correct answer: ACE inhibitors
ACE inhibitors reduce efferent arteriolar tone, critically reducing GFR in bilateral renal artery stenosis and risking acute kidney injury.
Question 4: Which cytochrome P450 enzyme is primarily responsible for metabolizing warfarin and many other drugs?
- CYP1A2
- CYP2C9 (Correct answer)
- CYP3A4
- CYP2D6
Correct answer: CYP2C9
CYP2C9 is the primary enzyme responsible for S-warfarin metabolism, and its inhibition or induction significantly affects INR.
Question 5: What is the mechanism of action of statins in lowering LDL cholesterol?
- Inhibiting bile acid reabsorption
- Blocking HMG-CoA reductase (Correct answer)
- Activating LDL receptors directly
- Inhibiting cholesterol absorption in the gut
Correct answer: Blocking HMG-CoA reductase
Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis, indirectly upregulating LDL receptors.
Question 6: A patient taking rifampin for tuberculosis has reduced efficacy of their oral contraceptive. Why?
- Rifampin inhibits CYP3A4
- Rifampin induces CYP3A4 (Correct answer)
- Rifampin blocks estrogen receptors
- Rifampin impairs GI absorption
Correct answer: Rifampin induces CYP3A4
Rifampin is a potent CYP3A4 inducer that accelerates metabolism of oral contraceptive hormones, reducing their plasma levels and efficacy.
SPEX SPEX Pharmacology 2
Which medication requires routine monitoring of serum drug levels due to its narrow therapeutic index?