Life threatening hyperkalemia and acidosis secondary to trimethoprim-sulfamethoxazole treatment

We present a 77-year-old male with moderate chronic renal insufficiency fro m diabetic nephropathy who developed severe metabolic acidosis and life thr eatening hyperkalemia on treatment with regular dose of trimethoprim-sulfam ethoxazole (TMP-SMZ) for urinary tract infection. The metabolic acidosis an d hyperkalemia resolved upon appropriate medical intervention and discontin uation of TMP-SMZ. While hyperkalemia has commonly been reported with high dose of TMP-SMZ, severe metabolic acidosis is quite uncommon with regular d ose TMP-SMZ. We emphasize that patients with renal tubular acidosis (RTA), renal insufficiency, aldosterone deficiency, old age with reduced renal mas s and function, and angiotensin converting enzyme (ACE)-inhibitor therapy a re at high risk of developing these severe and potentially life threatening complications.