Drug Interaction Report

MONITOR: Coadministration with ranolazine may increase the plasma concentrations of drugs that are primarily metabolized by the CYP450 3A4 isoenzyme. The mechanism is reduced clearance due to inhibition of CYP450 3A4 by ranolazine. The interaction may be significant for sensitive CYP450 3A4 substrates or those that demonstrate a narrow therapeutic index.

MANAGEMENT: Caution is advised if ranolazine is used in combination with sensitive CYP450 3A4 substrates or those that demonstrate a narrow therapeutic index (e.g., ergot alkaloids, colchicine, fentanyl, macrolide immunosuppressants, midazolam, triazolam, vinca alkaloids). Dosage adjustments as well as clinical and laboratory monitoring may be appropriate whenever ranolazine is added to or withdrawn from therapy.

GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of orally administered ranolazine. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because ranolazine prolongs QT interval in a dose-dependent manner, high plasma levels of ranolazine may increase the risk of ventricular arrhythmias such as ventricular tachycardia, ventricular fibrillation, and torsade de pointes.

MANAGEMENT: Patients treated with ranolazine should avoid consumption of grapefruit juice and other grapefruit products if possible. Otherwise, the dosage of ranolazine should be limited to 500 mg twice a day.

ADJUST DOSING INTERVAL: Consumption of food can decrease the rate and extent of gastrointestinal absorption of sirolimus. Also, the consumption of grapefruit juice may result in increased sirolimus trough concentrations.

MANAGEMENT: Experts recommend that this drug be taken either at least one hour prior to eating or consistently with or without food to avoid variations in sirolimus blood levels. The manufacturer recommends against using grapefruit juice for dilution of sirolimus doses. Patients should be monitored for clinical and laboratory evidence of altered immunosuppressant effects.