NBME Pharmacology 3

Question 1

A patient receives succinylcholine for rapid sequence intubation. Which condition represents an absolute contraindication to its use?

Accepted Answer

Crush injury 5 days ago

Answer

Denervation injuries or crush injuries cause upregulation of extrajunctional acetylcholine receptors; succinylcholine causes massive K+ efflux leading to fatal hyperkalemia.

Question 2

Which opioid analgesic is most appropriate for a patient with severe renal impairment requiring chronic pain management?

Accepted Answer

Fentanyl

Answer

Fentanyl is the preferred opioid in renal failure because it has no active metabolites that accumulate; morphine-6-glucuronide accumulates and causes toxicity in renal impairment.

Question 3

Methotrexate kills cancer cells primarily by inhibiting which enzyme?

Accepted Answer

Dihydrofolate reductase

Answer

Methotrexate competitively inhibits dihydrofolate reductase (DHFR), depleting tetrahydrofolate and blocking purine and thymidylate synthesis.

Question 4

A patient receiving cyclophosphamide for lymphoma develops painless hematuria. Which complication is occurring?

Accepted Answer

Hemorrhagic cystitis from acrolein metabolite

Answer

Cyclophosphamide is metabolized to acrolein, which accumulates in urine and causes direct urothelial damage resulting in hemorrhagic cystitis.

Question 5

Atropine is administered to reverse the effects of organophosphate poisoning. Which toxic effect of organophosphates does atropine NOT reverse?

Accepted Answer

Skeletal muscle paralysis

Answer

Atropine blocks muscarinic receptors but has no effect on nicotinic receptors at the neuromuscular junction; pralidoxime (2-PAM) must be used to reverse skeletal muscle effects.

NBME Practice Test

NBME Practice Test

NBME Pharmacology 3