COMLEX-USA Pharmacology 1 — Questions and Answers
Question 1: Which beta-blocker is cardioselective (beta-1 selective) and commonly used in heart failure?
- Propranolol
- Carvedilol
- Metoprolol succinate (Correct answer)
- Labetalol
Correct answer: Metoprolol succinate
Metoprolol succinate (extended-release) is a beta-1 selective blocker proven to reduce mortality in heart failure with reduced ejection fraction.
Question 2: The mechanism of action of metformin in type 2 diabetes primarily involves:
- Stimulating insulin secretion from beta cells
- Activating AMPK to reduce hepatic gluconeogenesis (Correct answer)
- Blocking SGLT-2 in the kidney
- Inhibiting dipeptidyl peptidase-4
Correct answer: Activating AMPK to reduce hepatic gluconeogenesis
Metformin activates AMPK, which decreases hepatic gluconeogenesis and increases peripheral insulin sensitivity without causing hypoglycemia.
Question 3: A patient taking warfarin is started on trimethoprim-sulfamethoxazole for a UTI. Which effect is expected?
- Decreased anticoagulation due to CYP induction
- Increased anticoagulation due to CYP2C9 inhibition (Correct answer)
- No change in INR
- Decreased warfarin absorption
Correct answer: Increased anticoagulation due to CYP2C9 inhibition
TMP-SMX inhibits CYP2C9, which metabolizes S-warfarin, leading to increased warfarin levels and elevated INR/bleeding risk.
Question 4: Which opioid analgesic is contraindicated in patients with renal failure due to accumulation of its active metabolite morphine-6-glucuronide?
- Fentanyl
- Hydromorphone
- Morphine (Correct answer)
- Buprenorphine
Correct answer: Morphine
Morphine's active metabolite morphine-6-glucuronide (M6G) accumulates in renal failure, causing prolonged sedation and respiratory depression.
Question 5: Atropine reverses bradycardia caused by organophosphate poisoning by which mechanism?
- Reactivating acetylcholinesterase
- Competitively blocking muscarinic receptors (Correct answer)
- Blocking nicotinic receptors
- Increasing sympathetic tone directly
Correct answer: Competitively blocking muscarinic receptors
Atropine competitively antagonizes muscarinic acetylcholine receptors, reversing the excess cholinergic (SLUDGE) effects of organophosphate poisoning.
Question 6: Which class of antibiotics inhibits bacterial cell wall synthesis by binding to PBPs and is bactericidal?
- Fluoroquinolones
- Macrolides
- Beta-lactams (Correct answer)
- Aminoglycosides
Correct answer: Beta-lactams
Beta-lactam antibiotics (penicillins, cephalosporins, carbapenems) bind penicillin-binding proteins (PBPs) to inhibit cell wall cross-linking, causing bacterial lysis.
COMLEX-USA Pharmacology 1
Which beta-blocker is cardioselective (beta-1 selective) and commonly used in heart failure?