Therapeutic Note(s)

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A low pH is necessary for absorption. Antacids, anticholinergics/antispasmodics, H2-blockers, and omeprazole may decrease absorption. Ketoconazole is a potent inhibitor of hepatic oxidation of drugs and may cause significant elevation of blood levels of astemizole, cisapride, cyclosporine, terfenadine, theophylline and warfarin. Potentially fatal arrhythmias (torsade de pointes) can occur with the combination of ketoconazole and astemizole, cisapride or terfenadine. Insulin requirements may be reduced. Hepatotoxicity occurs in approximately 1 in 1500 patients treated with ketoconazole for onychomycosis; female gender, pre-existing disease, alcoholism and greater than 2 weeks of therapy are pre-disposing factors.