Samidorphan was developed as a sublingually bioavailable µ-opioid receptor antagonist. This drug participated in clinical trials for the treatment of Schizophrenia, Alcohol Dependence, and Binge Eating Disorder. The oral dose pharmacokinetics, safety, and tolerability of samidorphan were evaluated in phase II double blind, placebo-controlled, randomized studies in healthy adults. In addition, the combination of samidorphan (SAM) with buprenorphine (BUP) was studied in phase III clinical trial in patients with major depressive disorder (MDM). It was shown that the long-term treatment did not reveal any new safety findings and confirmed that the risk of abuse and dependence with BUP/SAM was low.

Buprenorphine is an opioid analgesic, used to treat opioid addiction, moderate acute pain, and moderate chronic pain. Buprenorphine is a partial agonist at the mµ-opioid receptor and an antagonist at the kappa-opioid receptor. One unusual property of buprenorphine observed in vitro studies is its very slow rate of dissociation from its receptor. This could account for its longer duration of action than morphine, the unpredictability of its reversal by opioid antagonists, and its low level of manifest physical dependence. The principal action of the therapeutic value of buprenorphine is analgesia and is thought to be due to buprenorphine binding with high affinity to opioid receptors on neurons in the brain and spinal cord. Buprenorphine produces respiratory depression by direct action on brain stem respiratory centers. The respiratory depression involves a reduction in the responsiveness of the brain stem respiratory centers to both increases in carbon dioxide tension and electrical stimulation. Buprenorphine causes a reduction in motility associated with an increase in smooth muscle tone in the antrum of the stomach and duodenum. Digestion of food in the small intestine is delayed and propulsive contractions are decreased. Buprenorphine produces peripheral vasodilation, which may result in orthostatic hypotension or syncope. Manifestations of histamine release and/or peripheral vasodilation may include pruritus, flushing, red eyes, sweating, and/or orthostatic hypotension.