A 60-year-old woman comes to the office for a 3-day history of dysuria, urgency and frequency. Urinalysis show many WBCs in the urine speciman and nitrates positive. She has no fever and she is a sexual active with her partner. Physical examination shows no abnormalities. A trimethoprim-sulfamethoxazole is prescribed to treat her urinary tract infection. This patient is at greatest risk for which of the following drug-induced adverse effects?

Question

Quizplus · Accepted Answer

Eductional Objective: Hyperkalemia is a common adverse effect of trimethoprim-sulfamethoxazole due to the trimethoprim-induced blockade of the sodium channels in the collecting duct, which prevents sodium-potassium exchange and reduces renal excretion of potassium (similar to the action of amiloride).  This effect is often magnified in the elderly population, those with renal failure, or those given other potassium-sparing diuretics, ACE inhibitors, or angiotensin receptor blockers.

A 60-Year-Old Woman Comes to the Office for a 3-Day