Drug Interaction Report

MONITOR: When administered orally, lefamulin may increase the plasma concentrations of drugs that are primarily metabolized by the CYP450 3A4 isoenzyme. Based on interaction with midazolam, a sensitive CYP450 3A4 substrate, lefamulin may be a moderate CYP450 3A4 inhibitor. When oral midazolam was administered concomitantly with and at 2 or 4 hours after administration of lefamulin tablets, mean midazolam peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 100% and 200%, respectively. No clinically significant differences in the pharmacokinetics of midazolam were observed when administered concomitantly with lefamulin injection.

MANAGEMENT: Caution is advised when oral lefamulin is used concomitantly with drugs that are substrates of CYP450 3A4, particularly sensitive substrates or those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever oral lefamulin is added to or withdrawn from therapy. Patients should be monitored for the development of adverse effects. The prescribing information for concomitant medications should be consulted to assess the benefits versus risks of coadministration of a moderate CYP450 3A4 inhibitor like lefamulin and for any dosage adjustments that may be required.

ADJUST DOSING INTERVAL: Food may reduce the oral bioavailability of lefamulin. When a single 600 mg oral dose of lefamulin was administered with a high-calorie, high-fat breakfast (800 to 1000 calories; approximately 50% from fat), lefamulin peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by approximately 23% and 18%, respectively.

GENERALLY AVOID: Grapefruit juice may increase the oral bioavailability of lefamulin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but pharmacokinetic data are available for the potent CYP450 3A4 inhibitor, ketoconazole. When oral lefamulin was administered with oral ketoconazole, mean lefamulin peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 58% and 165%, respectively. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Increased exposure to lefamulin may increase the risk of QT interval prolongation, which has been associated with ventricular arrhythmias including torsade de pointes and sudden death.

MANAGEMENT: Lefamulin tablets should be taken at least one hour before or two hours after a meal. Patients should preferably avoid or limit the consumption of grapefruit and grapefruit juice during treatment with lefamulin.