Plasma conc may be affected by inhibitors or inducers of UDP glucuronidation (phase 2 enzymes) & P-gp efflux. Decreased Cmax
& AUC w/ rifabutin, efavirenz & phenytoin. May increase plasma levels of cytochrome P450 metabolized drugs. May increase plasma conc of terfenadine, astemizole, cisapride, pimozide & quinidine; ergot & vinca alkaloids, & digoxin. Increased Cmax
& AUC of tacrolimus; rifabutin; midazolam IV; atazanavir; simvastatin. Frequently monitor for adverse effects & toxicity related to Ca channel blockers. Decreased glucose conc w/ sulfonylureas (eg, glipizide). Oral susp: Decreased Cmax
& AUC w/ cimetidine, esomeprazole; if possible, avoid co-administration w/ H2
receptor antagonists, proton pump inhibitors & antacids. Decreased plasma conc w/ metoclopramide. Increased Cmax
& AUC of sirolimus. May decrease plasma conc w/ fosamprenavir. Increased cyclosporine conc (in heart transplant patients on stable doses of cyclosporine).