Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 1A2 may increase the plasma concentrations of pentoxifylline and its active hydroxy metabolite (M1), both of which are substrates of the isoenzyme. In a study consisting of eight healthy, nonsmoking volunteers, mean pentoxifylline systemic exposure (AUC) increased by approximately 35% when pentoxifylline 300 mg was administered intravenously one hour after a single 750 mg oral dose of ciprofloxacin, a moderate CYP450 1A2 inhibitor. The R- and S-enantiomers of the M1 metabolite also increased by 39% and 37%, respectively.

MANAGEMENT: Pharmacologic response to pentoxifylline should be monitored more closely whenever a potent or moderate CYP450 1A2 inhibitor is added to or withdrawn from therapy, and the pentoxifylline dosage adjusted as necessary. Patients should be advised to seek medical attention if they experience serious adverse effects such as bleeding, angina, or arrhythmias.