Severe hyponatremia and hyperkalemia induced by trimethoprim-sulfamethoxazole in patients with Pneumocystis carinii pneumonia.

An antimicrobial agent trimethoprim-sulfamethoxazole (Tmp-Smx) does not usually cause electrolyte disturbances at regular doses, and few cases of Tmp-Smx-induced electrolyte imbalance have been reported in the English-language literature to date. Recently, however, we treated two patients with Pneumocystis carinii pneumonia who developed severe hyponatremia and hyperkalemia on administration of high-dose Tmp-Smx. These electrolyte disturbances were attributable to the direct effect of Tmp-Smx on the renal distal tubules, were reversible, and corrected by infusion of a sodium-enriched and potassium-free liquid. Therefore, it is suggested that even after electrolyte disturbances have occurred, high-dose Tmp-Smx therapy may be continued for severe infectious diseases under appropriate electrolyte correction.