Trimethoprim-sulfamethoxazole induces reversible hyperkalemia

* Objective: To determine the effect of trimethoprim-sulfamethoxazole (Tmp-Smx) on serum potassium concentration. * Design: Retrospective cohort study. * Setting: An urban teaching hospital. * Patients: Fifty-one persons hospitalized for symptomatic infection with human immunodeficiency virus (HIV). Twenty-five patients who were taking high-dose Tmp-Smx (trimethoprim 20 mg/kg per day; sulfamethoxazole, 100 mg/kg per day) for Pneumocystis carinii pneumonia were the study group. Twenty-six patients who had not received the drug were the control group. Patients who received potassium supplements, those taking medications known to alter potassium homeostasis or renal function, or those with a serum creatinine level more than 186 [Mu] mol/L were excluded. * Measurements and Main Results: Serum potassium concentration in the study group was 4.1 [+ or -] 0.1 mmol/L (mean [+ or -] SE) and increased by 1.1 mmol/L (Cl, 0.8 to 1.5 mmol/L) (P < 0.0001) 9.8 [+ or -] 0.5 days after starting Tmp-Smx therapy. Patients followed longitudinally showed a progressive increase in serum potassium levels during therapy and a progressive decline after discontinuing Tmp-Smx. Blood urea nitrogen and serum creatinine levels increased mildly from 4.3 [+ or -] 0.5 mmol/L and 85 [+ or -] 6 [m u] mol/L to 6.4 [+ or -] 0.7 mmol/L and 113 [+ or -] 8 [m u] mol/L, respectively. The serum potassium level in the control group was 4.3 [+ or -] 0.1 mmol/L and remained unchanged during hospitalization. * Conclusions: High-dose Tmp-Smx therapy used for the treatment of P. carinii pneumonia in HIV-infected patients leads to an increase in the serum potassium concentration and may result in life-threatening hyperkalemia. Patients receiving high doses of Tmp-Smx require close monitoring of their serum potassium concentration, particularly 7 to 10 days after the start of therapy.
Treatment with high-dose trimethoprim-sulfamethoxazole (Tmp-Smx) for Pneumocystis carinii pneumonia may cause hyperkalemia in patients with HIV infection. Hyperkalemia is abnormally high blood levels of potassium. Among 51 patients hospitalized for HIV infection, 25 were treated with high-dose Tmp-Smx for P. carinii pneumonia and 26 were not been treated with Tmp-Smx (control group). Blood levels of potassium were similar in the two groups of patients before treatment with Tmp-Smx was begun. Potassium concentration increased progressively during treatment with Tmp-Smx among members of the treatment group, but declined after treatment was discontinued. Blood levels of potassium remained the same in patients from the control group. Patients treated with high-dose Tmp-Smx should be monitored closely for increases in their blood levels of potassium.