Drug Interactions between dutasteride / tamsulosin and lefamulin

ADJUST DOSING INTERVAL: Food may delay the gastrointestinal absorption of tamsulosin. The time to maximum plasma concentration (Tmax) is reached by 4 to 5 hours under fasted conditions and by 6 to 7 hours when tamsulosin is administered with food. The delay in Tmax has the desirable effect of smoothing the tamsulosin plasma concentration profile, thereby reducing fluctuation of the plasma peak and trough concentrations with multiple dosing. Food may also affect the extent of absorption of tamsulosin. It has been reported that taking tamsulosin under fasted conditions results in a 30% increase in bioavailability (AUC) and 40% to 70% increase in peak plasma concentration (Cmax) compared to fed conditions. The effects of food on the pharmacokinetics of tamsulosin are consistent regardless of whether tamsulosin is taken with a light meal or a high-fat meal.

MANAGEMENT: To ensure uniformity of absorption, tamsulosin should be administered approximately one-half hour following the same meal each day.

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.