Trimethoprim-sulfamethoxazole combined with spironolactone increases hyperkalemia risk

January 01, 0001

Trimethoprim-sulfamethoxazole combined with spironolactone increases hyperkalemia risk

These Canadian researchers examined hospital admissions due to hyperkalemia in geriatric patients treated with both trimethoprim- sulfamethoxazole and spironolactone. They performed a nested case-control study of patients taking spironolactone and admitted to hospital for hyperkalemia within 14 days of receiving a prescription for trimethoprim- sulfamethoxazole, amoxicillin, norfloxacin, or nitrofurantoin. Controls were matched for age, sex, chronic kidney disease and diabetes.

The researchers found: "During the 18 year study period, 6903 admissions for hyperkalaemia were identified, 306 of which occurred within 14 days of antibiotic use. Of these, 248 (81%) cases were matched to 783 controls. 10.8% (17?859/165?754) of spironolactone users received at least one prescription for trimethoprim-sulfamethoxazole. Compared with amoxicillin, prescription of trimethoprim-sulfamethoxazole was associated with a marked increase in the risk of admission to hospital for hyperkalaemia (adjusted odds ratio 12.4). The population attributable fraction was 59.7%, suggesting that approximately 60% of all cases of hyperkalaemia in older patients taking spironolactone and treated with an antibiotic for a urinary tract infection could be avoided if trimethoprim-sulfamethoxazole was not prescribed. Treatment with nitrofurantoin was also associated with an increase in the risk of hyperkalaemia (adjusted odds ratio 2.4), but no such risk was found with norfloxacin (adjusted odds ratio 1.6)"

The researchers concluded: "Among older patients receiving spironolactone, treatment with trimethoprim-sulfamethoxazole was associated with a major increase in the risk of admission to hospital for hyperkalaemia. This drug combination should be avoided when possible."

Trimethoprim-sulfamethoxazole markedly increases the risk of hyperkalemia in geriatric patients taking spironolactone

For the full abstract, click here.

BMJ 343:d5228, 12 September 2011 © 2011 BMJ Publishing Group Ltd.
Trimethoprim-sulfamethoxazole induced hyperkalaemia in elderly patients receiving spironolactone: nested case-control study. Tony Antoniou, Tara Gomes, Muhammad M Mamdani, et al. Correspondence to T Antoniou: [email protected]

Category: A. General/Unspecified. Keywords: Trimethoprim-sulfamethoxazole, hyperkalemia, spironolactone, elderly, potassium, nested case-control study, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 4 October 2011

Pearls are an independent product of the Cochrane primary care group and are meant for educational use and not to guide clinical care.

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