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Hyperkalemia in Elderly Patients Receiving Standard Doses of Trimethoprim-Sulfamethoxazole
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IN RESPONSE:
Before receiving the above correspondence, we were unaware of any case reports in which administration of trimethoprim-sulfamethoxazole in standard doses (160 mg of trimethoprim and 800 mg of sulfamethoxazole given twice daily) has been implicated as a cause of hyperkalemia. In fact, of the 649 patients who received trimethoprim-sulfamethoxazole in standard doses and who were monitored within a hospital setting in the Boston Collaborative Drug Surveillance Program, none developed hyperkalemia [1]. Trimethoprim-sulfamethoxazole inhibits amiloride-sensitive sodium channels in the distal nephron and reduces the transepithelial voltage favoring potassium secretion in a dose-dependent fashion [2, 3]. Standard twice-daily doses of trimethoprim-sulfamethoxazole may not maximally inhibit renal potassium excretion because the achievable urinary drug concentrations may only produce a 50% decrease in the electrical gradient [2, 3]. Other factors such as age-related reductions in renal function or defects in renal potassium handling may be required for standard doses of trimethoprim-sulfamethoxazole to express fully the hyperkalemic effect. Prospective studies are needed to examine this possibility.
Ira W. Reiser, MD
Shyan-Yih Chou, MD
The Brookdale Hospital Medical Center; Brooklyn, NY 11212
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 Unpublished letters cannot be returned.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
