Calcium channel blockers + macrolides: elderly patients hospitalised for low blood pressure.Prescrire Int. 2012 Jul; 21(129):182.PI
Macrolides that inhibit cytochrome P450 isoenzyme CYP 3A4 can lead to the accumulation of calcium channel blockers metabolised by the same isoenzyme and therefore an increase in their dose-related adverse effects. A Canadian case-control study examined the relationship between macrolide use and hospitalisation for hypotension (including shock) among 7100 elderly patients who were also taking a calcium channel blocker. The results showed more exposure to certain macrolides immediately prior to hospitalisation for hypotension than during an earlier control period; these macrolides included erythromycin (odds ratio (OR) = 5.8; 95% confidence interval: 2.3 to 15) and clarithromycin (OR = 3.7, 95% CI: 2.3 to 6.1). No such increase was found with azithromycin. In practice, patients treated with a calcium channel blocker should not be prescribed erythromycin or clarithromycin, but rather an antibiotic with similar efficacy but a lower risk of interaction.