Drug Interaction Report

MONITOR: Coadministration with alcohol or other central nervous system (CNS) depressants may enhance the sedative effects of allopurinol and increase the likelihood and/or severity of central nervous system (CNS) side effects, such as drowsiness, somnolence, vertigo, and ataxia.

MANAGEMENT: Caution for increased CNS adverse effects is advised if allopurinol is coadministered with alcohol, other CNS depressants, or agents that cause dizziness or vertigo. Patients should not drive, operate machinery, or engage in hazardous activities requiring mental alertness and motor coordination until they know how the medications affect them.

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of lemborexant, which is primarily metabolized by the isoenzyme. When coadministered with rifampin, a potent CYP450 3A4 inducer, lemborexant peak plasma concentration (Cmax) and systemic exposure (AUC) each decreased by at least 90%. No data are available for other, less potent CYP450 3A4 inducers.

MANAGEMENT: The potential for diminished pharmacologic effects of lemborexant should be considered during coadministration with CYP450 3A4 inducers. Alternative treatments may be required if an interaction is suspected.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of lemborexant, 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. When coadministered with itraconazole, a potent CYP450 3A4 inhibitor, lemborexant peak plasma concentration (Cmax) and systemic exposure (AUC) increased approximately 1.4-fold and 3.8-fold, respectively. When coadministered with fluconazole, a moderate CYP450 3A4 inhibitor, lemborexant Cmax and AUC increased approximately 1.6-fold and 4.2-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 lemborexant 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, nightmares, palpitations, or headache.

After administration of a high-fat, high-calorie meal (approximately 1000 calories with 500 to 600 calories from fat), lemborexant Cmax decreased by 23%, AUC increased by 18%, and the time to maximum concentration (Tmax) was delayed by 2 hours.

MANAGEMENT: 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. Patients should avoid consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with lemborexant.

ADJUST DOSING INTERVAL: The tolerability of allopurinol may be improved by giving it after a meal. Additionally, when the dose is greater than 300 mg, dividing the total daily dose into smaller doses administered more often may be appropriate to help minimize gastrointestinal irritation.

MONITOR: Concomitant use of allopurinol with central nervous system (CNS) depressants, including alcohol, may potentiate adverse effects such as somnolence and sedation.

MANAGEMENT: To improve tolerability, some manufacturers suggest administering allopurinol after a meal. Additionally, if the daily dose is greater than 300 mg, administering allopurinol in divided doses may help reduce gastrointestinal intolerance. Patients should also be counseled to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them.