Sulfamethoxazole-Trimethoprim-Induced Hyperkalemia in Hospitalized Patients Using Potassium-Sparing Drugs: An Observational Study.

The objective of this analysis is to investigate the risk of hyperkalemia in hospitalized patients using sulfamethoxazole-trimethoprim (Co-trimoxazole) and a potassium-sparing drug (potassium-sparing diuretic or renin-angiotensin system [RAS]-inhibitor). Researchers conducted a nested case control study within a cohort of hospitalized patients using a potassium-sparing diuretic and/or a RAS-inhibitor from the PHARMO Database Network. Researchers estimated the odds ratios (ORs) and 95% confidence intervals (CI) for the risk of hyperkalemia in patients receiving both Co-trimoxazole and a potassium-sparing drug compared with patients only receiving a potassium-sparing drug. Among a cohort of 25,849 patients, researchers identified 2054 cases of hyperkalemia during hospitalization in patients also using a potassium-sparing drug. Using Co-trimoxazole in addition to a potassium-sparing drug was associated with an increased risk of hyperkalemia in hospitalized patients (OR_adj = 1.65, 95% CI 1.26-2.16) compared with using only a potassium-sparing drug. There was a trend of a more pronounced association between hyperkalemia and the co-use of Co-trimoxazole and potassium-sparing drugs in patients with an estimated GFR of 15-29 mL/min (OR_adj = 3.15, 95% CI 1.29-7.70). The number needed to harm for hyperkalemia induced by adding Co-trimoxazole to patients receiving a potassium-sparing drug is 19.5. Using the combination of Co-trimoxazole with a potassium-sparing drug in hospitalized patients increases the risk of hyperkalemia compared with using only a potassium-sparing drug. Physicians and other prescribers should be aware of hyperkalemia and routinely monitor serum potassium levels in hospitalized patients using this combination of drugs.