Alcohol is one of the most popular substances used worldwide for thousands of years. Globally, harmful alcohol use continues to be a major public health and economic burden. The World Health Organization global status report attributed harmful alcohol use to 3 million deaths in 2016.In the United States, alcohol is the most used substance by people over the age of 12, with alcohol use disorder (AUD) affecting 14.5 million people in this age group. Hazardous alcohol use is associated with emergency room visits, overdose, driving fatalities and chronic medical conditions such as liver disease, heart disease, and hypertension.

Pharmacological interventions for AUD have expanded over the past few decades, including FDA approved and off-label medications such as naltrexone that have demonstrated efficacy in reducing alcohol cravings, consumption, and likelihood of relapse. However, the significant variability in response to treatment fuels ongoing interest in novel pharmacotherapy for AUD. A common approach involves repurposing readily available medications based on our understanding of AUD pathophysiology. In this study, we focus on the orexin system, which has been implicated in behaviors such as feeding, sleep-wake cycle, motivation, and reward associated with food, sex and substances including alcohol. The brain neuropeptides orexin A and orexin B originate in the hypothalamus and project throughout the central nervous system, activating G-protein-coupled receptors orexin 1 and 2 (OX1R and OX2R). While both orexin receptors are involved in addictive behaviors, OX1R signaling has a stronger association with reward processes whereas OX2R promotes arousal. Chronic alcohol exposure may lead to neuroadaptations in the orexin system, as observed in studies showing a positive correlation between orexin levels and severity of alcohol dependence and distress during alcohol withdrawal. Moreover, multiple animal studies have demonstrated efficacy of orexin antagonists in reducing alcohol craving, self-administration, and reinstatement of alcohol use induced by cues and stress.

The orexin antagonist lemborexant is FDA approved for treatment of insomnia. Lemborexant acts on both OX1R and OX2R and has shown efficacy in sleep initiation and maintenance compared to placebo on polysomnography and patient-report. It has demonstrated long-term safety and effectiveness without physical dependence or rebound insomnia. Compared to suvorexant, another orexin antagonist, lemborexant has greater selectivity and stronger binding for orexin receptors. Suvorexant has secondary effects on the adenosine receptor and dopamine transporter whereas lemborexant only has weak binding to melatonin 1. These differences may increase risk of misuse for suvorexant more than lemborexant. In addition, Lemborexant's longer half-life (17-19h) may be advantageous for reduction of cravings during the day.

In people with AUD, insomnia is a common problem that is associated with alcohol craving and relapse. Standard treatment for AUD with naltrexone improves cravings and other AUD outcomes, but does not improve sleep. In some cases, naltrexone may have a detrimental effect on sleep. Lemborexant may be able to target both alcohol craving/urges and insomnia when added to standard treatment with naltrexone.