Trimethoprim-induced hyperkalemia: An analysis of reported cases

Trimethoprim has been recently implicated in the development of hyperkalemia when administered at standard doses to immunocompetent patients. However, many clinicians are unaware of this potentially dangerous adverse effect.

To review reported cases of trimethoprim-induced hyperkalemia in immunocompetent patients and identify predisposing factors, treatment, and outcome.

A MEDLINE literature search was performed using the key words 'trimethoprim' and 'hyperkalemia'. All English-language case reports and bibliographies of immunocompetent patients with trimethoprim-induced hyperkalemia were reviewed.

Nine cases were identified. The mean patient age was 77.6 years, and the mean duration of therapy was 10.2 days. Seven patients received standard oral dosages of trimethoprim-sulfamethoxazole for common infections, and 2 patients were concurrently receiving angiotensin-converting enzyme inhibitors. The mean pretreatment levels of creatinine and potassium were 1.01 mg/dl and 4.55 mmol/l, respectively. The mean peak serum potassium level was 7.0 mmol/l. No deaths attributable to hyperkalemia occurred.

Hyperkalemia due to trimethoprim typically affects elderly patients administered standard oral dosages, even in the presence of a normal serum creatinine level. Concurrent angiotensin-converting enzyme inhibitor therapy may increase the risk of hyperkalemia. The prognosis is favorable with standard therapy for hyperkalemia and withdrawal of trimethoprim.