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Hyperkalemia and Trimethoprim-Sulfamethoxazole
- Michael Postelnick, BS, RPh;
- William Budris, BS, RPh; and
- Gary A. Noskin, MD
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TO THE EDITOR:
Alappan and colleagues have shown that serum potassium levels significantly increase in patients receiving standard doses of trimethoprim-sulfamethoxazole [1]. Clinically significant hyperkalemia was more likely to occur in patients with some degree of renal insufficiency (serum creatinine level >106 mmol/L). Patients without renal insufficiency, although showing a similar absolute increase in serum potassium levels, were less likely to develop clinically significant hyperkalemia. This finding is not unexpected, given the amiloride-like action of trimethoprim in the distal tubule and the proven association between renal insufficiency and hyperkalemia due to amiloride use [2]. The authors, however, did not show any additive effect of other potassium-altering medications in causing the resultant elevation of serum potassium levels. This finding may be due to the definition of potassium-altering medications used in the study. If clinically significant drug interactions associated with amiloride that are known to result in hyperkalemia are used as a guide, only angiotensin-converting enzyme inhibitors, other potassium-sparing diuretics, and potassium supplementation should be used. The presence of concurrent renal insufficiency has been shown to enhance these interactions [3]. A reanalysis of the authors' data—one that identifies patients receiving the described medications and excluding patients whose potassium-altering medications consisted solely of heparin, digoxin, or a nonsteroidal anti-inflammatory drug—may clarify the expected additive interaction of trimethoprim and potassium-altering medications. Such a reanalysis may help clarify the role that renal insufficiency plays in this interaction. This information may help identify patients at significantly greater risk for hyperkalemia induced by trimethoprim-sulfamethoxazole.
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
