Reduced absorption w/ antimuscarinics, antacids, H2-blockers, PPIs, sucralfate. Reduced plasma concentrations w/ rifampicin, isoniazid, efavirenz, nevirapine, phenytoin. May also reduce concentrations of isoniazid and rifampicin. May reduce efficacy of oral contraceptives. May increase serum levels of CYP3A4 substrates e.g. digoxin, oral anticoagulants, sildenafil, tacrolimus. Potentially Fatal: May potentiate and prolong sedative and hypnotic effects of midazolam and triazolam. Increased plasma levels and prolonged QT intervals of astemizole, cisapride, dofetilide, pimozide, quinidine and terfenadine which may lead to torsade de pointes. Increased risk of myopathy w/ HMG-CoA reductase inhibitors (e.g. lovastatin, simvastatin). Markedly increased plasma levels of nisoldipine. Increased risk of...
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