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Pimozide (Orap) is a neuroleptic that is often used for psychogenic dermatologic problems, such as delusions of parasitosis. Case reports suggest that pimozide prolongs the cardiac QT interval and may lead to arrhythmias. Pimozide, like terfenadine (Seldane), is metabolized by the liver and gut cytochrome P450 3A4 (CYP3A4) system. Inhibitors of CYP3A4, such as erythromycin, clarithromycin, and ketoconazole may increase the risk of arrhythmia by decreasing clearance of pimozide and increasing serum concentrations. To examine this interaction, investigators from Georgetown University administered a single oral dose of pimozide (6 mg) with and without clarithromycin to 12 healthy subjects who were documented as extensive or poor metabolizers o…