Macrolides and Ketolides Erythromycin, clarithromycin, and telithromycin inhibit CYP3A4, the hepatic P450 enzyme that metabolizes many drugs, including cyclosporine, certain statins (lovastatin, simvastatin), theophylline, carbamazepine, warfarin, certain antineoplastic agents (., vincristine, irinotecan), and ergot alkaloids. In ~10% of patients receiving digoxin, concentrations increase significantly when erythromycin or telithromycin is coadministered, and this increase may lead to digoxin toxicity. Azithromycin has little effect on the metabolism of other drugs. Many drugs (., azole antifungal drugs, diltiazem, verapamil, and nefazodone) can also increase absorption or inhibit erythromycin metabolism. .
