Beta-blockers and TMP-SMX can interact, so the researchers had suspected that patients taking both drugs would be at increased risk of hyperkalemia. However, the increase in hyperkalemia with TMP-SMX did not appear any greater in patients who were also taking beta-blockers.

In conducting the study, the researchers used the extensive Ontario health administrative databases. "Without the use of this powerful resource, quantifying this adverse drug reaction would not have been possible," says Weir.

The study had some important limitations ”as in all observational studies, the patients were not randomly assigned to different antibiotics. "Also, data regarding factors that can predispose to hyperkalemia, such as diet and levels of physical activity were not available to us," notes Weir. He points out that the results may not be applicable to younger patients.

Source: American Society of Nephrology