Drug Interactions between daridorexant and halofantrine

GENERALLY AVOID: Grapefruit juice may increase the plasma concentration of halofantrine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. After administration of 500 mg with 250 mL regular-strength grapefruit juice daily for 3 days, average halofantrine AUC increased 2.8-fold and peak plasma concentrations increased 3.2-fold, compared to water, in healthy subjects (n=12). QT interval prolongation increased from an average of 17 ms with water to 31 ms with grapefruit juice. Halofantrine, even at recommended doses, can cause dose-related prolongation of the QT interval, resulting in an elevated risk of potentially fatal ventricular arrhythmias including ventricular tachycardia and torsade de pointes.

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of halofantrine. Peak plasma concentrations increased seven-fold and AUC increased three-fold in healthy subjects when halofantrine was administered with high-fat food.

MANAGEMENT: The authors of the study recommend that grapefruit juice be avoided during halofantrine therapy. The manufacturer recommends performing an ECG before initiating halofantrine therapy and cardiac monitoring during and for 8 to 12 hours after completion of therapy. Halofantrine should be taken on an empty stomach at least 1 hour before or 2 hours after food.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of daridorexant, which is primarily metabolized by CYP450 3A4. 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 has been reported for other CYP450 3A4 inhibitors. Per physiologically based pharmacokinetic (PBPK) analysis, concomitant use of itraconazole, a potent CYP450 3A4 inhibitor, increased daridorexant systemic exposure (AUC) by more than 400%. When a 25 mg daridorexant dose was coadministered with multiple 240 mg doses of diltiazem, a moderate CYP450 3A4 inhibitor, daridorexant peak plasma concentration (Cmax) and AUC increased by 1.4- and 2.4-fold, 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 daridorexant may increase the risk of adverse reactions such as central nervous system (CNS) depression, sleep paralysis, hallucinations, complex sleep behaviors, worsening of depression or suicidal ideation, or headache.

After administration of a high-fat, high-calorie meal, daridorexant Cmax decreased by 16% (no effect on AUC) and the time to maximum concentration (Tmax) was delayed by 1.3 hours.

GENERALLY AVOID: Alcohol may potentiate the pharmacologic effects of daridorexant. Coadministration of daridorexant (50 mg) with alcohol led to additive effects on psychomotor performance. Use in combination may result in an increased risk of complex sleep-related behaviors (e.g., "sleep driving"), additive central nervous system (CNS) depression, and/or impairment of psychomotor performance.

MANAGEMENT: Consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with daridorexant should generally be avoided. Some authorities suggest avoiding grapefruit or grapefruit juice consumption specifically in the evening. Patients should avoid the consumption of alcohol during treatment with daridorexant. The manufacturer makes no recommendation regarding administration with food; however, the time to sleep onset may be delayed if taken with or soon after a meal.