Drug Interaction Report

MONITOR: Coadministration with delavirdine 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 delavirdine inhibition of intestinal and hepatic CYP450 3A4, the isoenzyme primarily responsible for the metabolic clearance of most calcium channel blockers.

MANAGEMENT: Close monitoring of clinical response and tolerance is recommended if calcium channel blockers are used in combination with delavirdine. Dosage reduction may be required for the calcium channel blocker, particularly if it is a dihydropyridine. Patients should be advised to seek medical attention if they experience edema or swelling of the lower extremities; sudden, unexplained weight gain; difficulty breathing; chest pain or tightness; or hypotension as indicated by dizziness, fainting, or orthostasis.