Buprenorphine, sold under the brand name Subutex, among others, is an opioid used to treat opioid addiction, acute pain, and chronic pain. It can be used under the tongue, by injection, as a skin patch, or as an implant. For opioid addiction it is typically only started when withdrawal symptoms have begun and for the first two days of treatment under direct observation of a health care provider. For longer term treatment of addiction a combination formulation of buprenorphine/naloxone is recommended to prevent misuse by injection. Maximum pain relief is generally within an hour with effects up to 24 hours.Side effects may include respiratory depression (decreased breathing), sleepiness, adrenal insufficiency, QT prolongation, low blood pressure, allergic reactions, and opioid addiction. Among those with a history of seizures, there is a risk of further seizures. Opioid withdrawal following stopping buprenorphine is generally less severe than with other opioids. It is unclear if use during pregnancy is safe and use while breastfeeding is not recommended. Buprenorphine affects different types of opioid receptors in different ways. Depending on the type of receptor it may be an agonist, partial agonist, or antagonist.Buprenorphine was approved for medical use in the United States in 1981. In 2012, 9.3 million prescriptions for the medication were written in the United States. Buprenorphine may also be used recreationally by injection or in the nose for the high it produces. Occasionally it is used recreationally instead of heroin. In the United States it is a Schedule III controlled substance. For the tablets the wholesale cost in the United States is between US$0.86 and US$1.32 per daily dose as of 2017.