title: Calcium channel blockers + macrolides: elderly patients hospitalised for low blood pressure.
abstract: 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.
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000009:adverse effects*; D017291:Clarithromycin / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A; D065692:Cytochrome P-450 CYP3A Inhibitors; D004347:Drug Interactions; D004917:Erythromycin / Q000494:pharmacology; D006760:Hospitalization; D006801:Humans; D007022:Hypotension / Q000139:chemically induced*; D018942:Macrolides / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002121:Calcium Channel Blockers; D065692:Cytochrome P-450 CYP3A Inhibitors; D018942:Macrolides; D004917:Erythromycin; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D017291:Clarithromycin