Buprenorphine: a primer for emergency physicians.

The recent approval of office-based treatment for opioid addiction and US Food and Drug Administration approval of buprenorphine will expand treatment options for opioid addiction. Buprenorphine is classified as a partial micro opioid agonist and a weak kappa antagonist. It has a high affinity for the micro receptor, with slow dissociation resulting in a long duration of action and an analgesic potency 25 to 40 times more potent than morphine. At higher doses, its agonist effects plateau and it begins to behave more like an antagonist, limiting the maximal analgesic effect and respiratory depression. This "ceiling effect" confers a high safety profile clinically, a low level of physical dependence, and only mild withdrawal symptoms on cessation after prolonged administration. Suboxone contains a mixture of buprenorphine and naloxone. The naloxone is poorly absorbed sublingually and is designed to discourage intravenous use. Subutex, buprenorphine only, will also be available primarily as an initial test dose. Clinicians will be using this drug for detoxification or for maintenance of opioid addiction. Patients with recent illicit opioid use may develop a mild precipitated withdrawal syndrome with the induction of buprenorphine. Acute buprenorphine intoxication may present with some diffuse mild mental status changes, mild to minimal respiratory depression, small but not pinpoint pupils, and relatively normal vital signs. Naloxone may improve respiratory depression but will have limited effect on other symptoms. Patients with significant symptoms related to buprenorphine should be admitted to the hospital for observation because symptoms will persist for 12 to 24 hours.