Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of ivabradine, which is primarily metabolized by the isoenzyme. According to the product labeling, potent CYP450 3A4 inhibitors such as ketoconazole and josamycin have been shown to increase ivabradine systemic exposure (AUC) by approximately 7- to 8-fold, and moderate CYP450 3A4 inhibitors such as diltiazem, verapamil and grapefruit juice have been shown to increase ivabradine systemic AUC by approximately 2- to 3-fold. Elevated plasma levels of ivabradine may increase the risk of excessive bradycardia and conduction disturbances.

MANAGEMENT: Caution is advised when ivabradine is prescribed with CYP450 3A4 inhibitors. Patients should be monitored for adverse effects such as bradycardia and atrial fibrillation, and the dosage of ivabradine adjusted as necessary in accordance with the product labeling.

GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of ivabradine. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. According to the product labeling, administration with grapefruit juice (quantity unknown) resulted in an approximately twofold increase in ivabradine systemic exposure (AUC). Elevated plasma levels of ivabradine may increase the risk of excessive bradycardia and conduction disturbances.

ADJUST DOSING INTERVAL: Food delays the absorption of ivabradine by approximately 1 hour and increases plasma exposure by 20% to 40% compared to fasting conditions.

MANAGEMENT: Patients treated with ivabradine should avoid or limit consumption of grapefruit or grapefruit juice. The manufacturer recommends taking ivabradine with meals to reduce variability in exposure.