PSA Adverse Drug Reactions 3

Question 1

A patient develops a persistent dry cough 3 weeks after starting ramipril for hypertension. What is the most appropriate management?

Accepted Answer

Switch to an angiotensin receptor blocker

Answer

ACE inhibitor-induced cough is caused by bradykinin accumulation and does not resolve with dose reduction; switching to an ARB avoids bradykinin-related effects entirely.

Question 2

Metformin should be withheld in patients with an eGFR below which threshold due to the risk of lactic acidosis?

Accepted Answer

30 mL/min/1.73m²

Answer

Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² because impaired renal clearance leads to drug accumulation and risk of potentially fatal lactic acidosis.

Question 3

A patient on simvastatin 40 mg starts clarithromycin for a chest infection and develops severe myalgia with dark urine. What is the most likely mechanism?

Accepted Answer

Clarithromycin inhibits CYP3A4, raising simvastatin plasma levels

Answer

Clarithromycin is a potent CYP3A4 inhibitor that markedly increases simvastatin exposure, precipitating statin-induced myopathy and potentially rhabdomyolysis.

Question 4

NSAIDs precipitate acute kidney injury primarily through which mechanism?

Accepted Answer

Inhibition of prostaglandin-mediated afferent arteriolar vasodilation

Answer

NSAIDs inhibit prostaglandin synthesis, abolishing the afferent arteriolar vasodilation that maintains glomerular filtration rate when renal perfusion pressure is reduced.

Question 5

A patient on warfarin has their INR rise from 2.5 to 5.8 after starting trimethoprim for a UTI. What is the primary mechanism of this interaction?

Accepted Answer

Trimethoprim inhibits CYP2C9, reducing S-warfarin metabolism

Answer

Trimethoprim inhibits CYP2C9, the primary enzyme metabolizing the more potent S-warfarin enantiomer, leading to drug accumulation and supratherapeutic anticoagulation.

(PSA) Prescribing Safety Assessment Practice Test

(PSA) Prescribing Safety Assessment Practice Test

PSA Adverse Drug Reactions 3