Daridorexant did not produce signs of withdrawal or dependence upon discontinuation in animal studies and clinical trials, and orexin receptor antagonists are not associated with rebound insomnia. Loss of sleep-promoting effectiveness occurs rapidly upon discontinuation of daridorexant. Preclinical research has suggested that orexin antagonists may reduce appetite, but daridorexant and other orexin antagonists have not been associated with weight loss in rigorous clinical trials.Orexin receptor antagonists can affect the reward system and produce drug-liking responses in humans. Daridorexant at a dose of 50 mg (the maximum recommended dose) showed significantly greater drug liking than placebo but significantly less drug liking than zolpidem (30 mg) and suvorexant (150 mg) in recreational sedative drug users. At higher doses of 100 and 150 mg (greater than the recommended maximum dose), drug liking with daridorexant was similar to that with zolpidem (30 mg) and suvorexant (150 mg). In other studies, suvorexant showed similar drug liking compared to zolpidem but lower misuse potential on other measures (e.g., overall rate of misuse potential adverse events of 58% for zolpidem and 31% for suvorexant in recreational drug users). No reports indicative of misuse liability were observed in large clinical trials with daridorexant, although these studies excluded participants with history of drug or alcohol misuse. Overdose
There is limited clinical experience with overdose of daridorexant. Overdose of the medication at a dose of up to four times the maximum recommended dose may result in adverse effects including somnolence, muscle weakness, catalepsy-like symptoms, sleep paralysis, attention disturbances, fatigue, headache, and constipation.
Mechanism of action
The endogenous orexin neuropeptides, orexin A and orexin B, are involved in the regulation of sleep–wake cycles and act to promote wakefulness. Deficiency of orexin signaling is thought to be the primary cause of the sleep disorder narcolepsy. Disturbances in orexin signaling may also be involved in insomnia. Research suggests that orexin signaling may change with age, and this has been implicated in age-related sleep disturbances. By blocking the actions of orexins and modulating sleep–wake cycles, orexin receptor antagonists like daridorexant reduce wakefulness and improve sleep. The sleep-promoting effects of dual orexin receptor antagonists are thought to be mediated specifically by blockade of the OX2 receptor in the lateral hypothalamus. Although narcoleptic symptoms were a theoretical concern during the development of orexin receptor antagonists, this has not been observed in clinical trials of these agents. Pharmacokinetics
Absorption
The absolute bioavailability of daridorexant is 62%. It reaches peak concentrations within 1 to 2 hours following a dose. Food prolonged the time to peak by 1.3 hours and decreased the peak concentrations by 16%, but did not affect area-under-the-curve concentrations. Distribution
The volume of distribution of daridorexant is 31 L. Its plasma protein binding is 99.7%. The plasma-to-blood ratio of daridorexant is 0.64. Daridorexant effectively crosses the blood–brain barrier in animals. Metabolism
Daridorexant is extensively metabolized primarily by CYP3A4 (89%). Other cytochrome P450 enzymes contribute individually to less than 3% of the clearance of daridorexant. Elimination
Daridorexant is eliminated primarily by feces (57%) then by urine (28%).