Coadministration with the hepatitis C virus (HCV) NS3/4A protease inhibitors, boceprevir and telaprevir, may increase the plasma concentrations and pharmacologic effects of calcium channel blockers, especially the dihydropyridines (e.g., amlodipine,
felodipine, nicardipine, nifedipine, nisoldipine). The mechanism involves inhibition of intestinal and hepatic CYP450 3A4, the isoenzyme primarily responsible for the metabolic clearance of most calcium channel blockers.