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Hyperkalemia in Elderly Patients Receiving Standard Doses of Trimethoprim-Sulfamethoxazole
- David H. Canaday, MD; and
- James R. Johnson, MD
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TO THE EDITOR:
High-dose trimethoprim-sulfamethoxazole therapy has recently been reported to induce reversible hyperkalemia by an amiloride-like action [1-3]. We report a case of reversible hyperkalemia associated with standard doses of trimethoprim-sulfamethoxazole.
An 84-year-old woman with chronic pulmonary disease admitted to the University of Minnesota Hospital with Haemophilus influenzae pneumonia was given intravenous trimethoprim-sulfamethoxazole, 160 mg and 800 mg, respectively, every 12 hours (total, 6.5 mg/kg per day) for four doses, followed by an oral preparation at the same dose. Her serum potassium concentration, which at admission had been 3.6 mmol/L, increased progressively to 5.3 mmol/L by 72 hours of trimethoprim-sulfamethoxazole therapy. Therapy was changed to amoxicillin, and her potassium level dropped to 4.6 mmol/L within 24 hours.
Therapy with trimethoprim-sulfamethoxazole was resumed after a 24-hour period, and, within 36 hours, her serum potassium concentration again rose to 5.3 mmol/L. Because of this reproducible increase in serum potassium concentration, amoxicillin was substituted for the duration of treatment. Eleven days after discharge, her potassium concentration had fallen to 4.5 mmol/L. Of note, her serum creatinine concentration during her hospitalization was 0.8 mg/dL, and her estimated creatinine clearance (from the modified Cockcroft-Gault equation) was 32 mL/min. While in the hospital, except for the antibiotics and a 50-mEq supplement of potassium chloride given intravenously during the first 24 hours, the patient received only her usual outpatient medications.
This case suggests that in some patients, standard doses of trimethoprim-sulfamethoxazole (one double-strength tablet twice daily) can raise the serum potassium concentration. This dose is less than half of that commonly used to treat Pneumocystis carinii pneumonia [1]. Medina and colleagues [1] noted that hyperkalemia developed in 20% of patients receiving high-dose trimethoprim-sulfamethoxazole (20 mg/kg per day of trimethoprim) for P. carinii pneumonia. Greenberg and colleagues [2] also documented a reversible rise in serum potassium concentrations with high-dose trimethoprim-sulfamethoxazole therapy. Clinicians should be alert to the possibility of hyperkalemia in patients receiving standard doses of this antibiotic.
David H. Canaday, MD
James R. Johnson, MD
University of Minnesota Medical School; Minneapolis, MN 55455
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
