<p>Reduced levels/effects with antacids, phenobarbital, carbamazepine, aminoglutethimide, phenytoin, rifampicin, nafcillin, nevirapine, omeprazole, nevirapine. Increased serum levels/effects with azole antifungal agents, cimetidine, efavirenz. Increased serum levels/effects of azithromycin, calcium channel blockers, clarithromycin, corticosteroids (e.g. fluticasone), mirtazapine, nateglinide, nefazodone, ciclosporin, sirolimus, tacrolimus, venlafaxine, eplerinone, fentanyl, atorvastatin, phosphodiesterase-5 (PDE-5) inhibitors, rifabutin, trazodone, TCAs. Reduced serum levels/effects of hormonal contraceptives, methadone, theophylline derivatives.</p>