Daridorexant

Indications

• FDA-approved in 2022 for the treatment of insomnia characterized by difficulties with sleep onset, sleep maintenance, or both, in adults.
• Pivotal phase 3 trials showed improvement in objective and subjective sleep measures plus daytime functioning at the 50 mg dose.
• Its roughly 8-hour half-life is the shortest among orexin antagonists, which limits next-day carryover relative to lemborexant.
• Reasonable when Z-drugs are contraindicated after a complex sleep behavior or when benzodiazepine exposure should be avoided.
• Off-label interest exists in insomnia comorbid with anxiety or depression, where orexin antagonists are under active study.
• Contraindicated in narcolepsy, since orexin transmission is already deficient and further blockade worsens the disorder.

Mechanism of action

• Dual orexin receptor antagonist that competitively blocks orexin A and orexin B binding at both OX1R and OX2R.
• Suppresses the hypothalamic wake drive to histaminergic, noradrenergic, serotonergic and cholinergic arousal nuclei rather than sedating broadly.
• Sleep architecture is largely preserved with proportional increases across sleep stages, including REM, unlike benzodiazepine hypnotics.
• No activity at GABA-A receptors, so there is no muscle relaxation, no anticonvulsant effect and less amnesia than with Z-drugs.
• Rapid receptor dissociation combined with a short half-life is intended to deliver overnight effect without morning residual blockade.

Pharmacokinetics

• Rapidly absorbed with peak concentrations at 1-2 hours and absolute bioavailability of about 62 percent after oral dosing.
• Elimination half-life is roughly 8 hours, about half that of lemborexant, which is the basis of its lower carryover profile.
• Metabolized almost entirely by CYP3A4, accounting for about 89 percent of clearance, with excretion split between feces and urine.
• A high-fat high-calorie meal delays the peak by about 1.3 hours and lowers peak concentration, blunting the sleep-onset effect.
• Exposure roughly doubles in moderate hepatic impairment, which caps the dose; pharmacokinetics are unchanged in renal impairment.

Dosing

• Adults: 25 or 50 mg PO once nightly within 30 minutes of going to bed, with at least 7 hours remaining before planned awakening.
• The 50 mg dose is the labeled maximum and is the dose that carried the daytime functioning benefit in the phase 3 program.
• With a moderate CYP3A4 inhibitor such as verapamil, diltiazem or fluconazole, the maximum recommended dose is 25 mg nightly.
• Concomitant use with strong CYP3A4 inhibitors such as ketoconazole, itraconazole or clarithromycin should be avoided.
• Moderate hepatic impairment: maximum 25 mg nightly; use in severe hepatic impairment is not recommended. No renal adjustment is needed.
• No taper is required on stopping, and neither rebound insomnia nor a withdrawal syndrome has been demonstrated in trials.

Adverse effects

• Headache in about 6-7 percent and somnolence or fatigue in about 6 percent, with nausea and dizziness less frequent.
• Next-morning residual sleepiness is less than with lemborexant or suvorexant, but driving impairment can still occur at 50 mg.
• Sleep paralysis, hypnagogic and hypnopompic hallucinations, and mild cataplexy-like leg weakness attributable to orexin blockade.
• Complex sleep behaviors including sleepwalking and sleep-driving have been reported and require immediate discontinuation.
• Worsening of depression and suicidal ideation have been reported with hypnotics generally; assess mood before and during treatment.
• Additive respiratory depression with opioids and alcohol, and caution is warranted in severe sleep apnea or advanced COPD.

Monitoring

• Assess next-morning alertness and driving safety after initiation and after any dose increase to 50 mg nightly.
• Ask specifically about sleep paralysis, hallucinations at sleep transitions, leg weakness and any complex sleep behaviors.
• Screen for depression and suicidal ideation before starting and at each follow-up visit during ongoing therapy.
• Evaluate and treat obstructive sleep apnea, restless legs, alcohol use and chronic pain before or alongside hypnotic therapy.
• Check the prescription monitoring program before prescribing this schedule IV agent and reassess ongoing need periodically.

Interactions

• Avoid concomitant strong CYP3A4 inhibitors; moderate inhibitors require the reduced maximum dose of 25 mg nightly.
• Strong and moderate CYP3A4 inducers including rifampin, carbamazepine, phenytoin and efavirenz markedly reduce exposure and efficacy.
• Additive sedation and respiratory depression with opioids, alcohol, benzodiazepines, gabapentinoids and sedating antihistamines.
• Contraindicated in narcolepsy; use caution in patients with compromised respiratory function or untreated severe sleep apnea.
• No clinically meaningful interaction with citalopram was observed, making combination with an SSRI generally straightforward.

Special populations

• Pregnancy: human data are insufficient; animal studies showed no clear teratogenicity but exposure margins were modest.
• Lactation: daridorexant is present in animal milk and human data are lacking; monitor a nursing infant for sedation and poor feeding.
• Pediatrics: safety and effectiveness under age 18 are not established and use is not recommended in that age group.
• Older adults: studied in adults 65 and older with efficacy maintained; it is not among the agents the AGS Beers Criteria flag for avoidance.
• Hepatic and renal impairment: cap at 25 mg in moderate hepatic disease and avoid in severe; no renal dose adjustment is needed.

Clinical pearls

• Shortest half-life of the orexin antagonists at about 8 hours, so less morning carryover.
• The 50 mg dose carried the daytime functioning benefit; 25 mg is mainly a sleep measure dose.
• Like the whole class, absolutely contraindicated in narcolepsy and a schedule IV substance.