Drug Interaction Report

GENERALLY AVOID: Based on in vitro inhibition data, coadministration with dalfopristin-quinupristin may increase the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme, including certain agents that can cause prolongation of the QTc interval (e.g., cisapride, disopyramide, pimozide, quinidine, tacrolimus). High plasma levels of these agents have been rarely associated with ventricular arrhythmias including ventricular tachycardia, ventricular fibrillation, and torsade de pointes, as well as cardiac arrest and sudden death.

MANAGEMENT: Given the potential for serious and life-threatening adverse cardiac events associated with increased plasma levels of agents that may prolong the QTc interval, concomitant use with dalfopristin-quinupristin should be avoided if they are known to be substrates of CYP450 3A4.