Drug Interaction Report

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of ivabradine and its active N-desmethylated metabolite, both of which are primarily metabolized by the isoenzyme. In 12 healthy volunteers, administration of a single 10 mg dose of ivabradine following pretreatment with the potent CYP450 3A4 inducer St. John's wort (300 mg three times daily for 14 days) decreased mean ivabradine peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 53% and 62%, respectively, compared to administration of ivabradine alone. Mean Cmax and AUC of the N-desmethylated metabolite, which is equipotent to ivabradine and circulates at concentrations approximately 40% that of ivabradine, decreased by 25% and 32%, respectively. The extent to which other, less potent inducers of CYP450 3A4 may interact with ivabradine is unknown.

MANAGEMENT: Caution is advised during concomitant use of ivabradine with CYP450 3A4 inducers. The potential for decreased efficacy of ivabradine should be considered.

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.

ADJUST DOSING INTERVAL: Certain penicillins may exhibit reduced gastrointestinal absorption in the presence of food. The therapeutic effect of the antimicrobial may be reduced.

MANAGEMENT: The interacting penicillin should be administered one hour before or two hours after meals. Penicillin V and amoxicillin are not affected by food and may be given without regard to meals.