A patient is taking ketoconazole for fungal infection develops cold for which he is prescribed terfenadine. Possible interaction between terfenadine and ketoconazole is: (A) Ketoconazole decreases metabolism of terfenadine, (B) Terfenadine increases levels of ketoconazole, (C) Ketoconazole decreases levels of terfenadine, (D) No interaction
Answer is A. (A) Ketoconazole decreases metabolism of terfenadine# Large amounts of Terfenadine reach systemic circulation if erythromycin, ketoconazole, clarithromycin are concurrently administered, as these drugs are P450 enzyme inhibitors.> Azithromycin, fluconazole have no effect & found to be safe.