Buprenorphine works the opioid receptors in the brain, the same receptors that are activated when you take other opioids like Oxycodone, methadone or heroin. Drugs that bind to these receptors tend to produce feelings of pleasure, numbing pain in the body and sometimes even producing a euphoric effect at a high enough dose.

The three main groups of opioid receptors in the brain are mu, kappa and delta. Buprenorphine is an unusual opioid in that it only partially activates the mu opioid receptor in the brain and actually antagonises the kappa receptor, preventing further uptake of opioids into the brain. This means that once levels of buprenorphine in the brain reach a certain limit, the opioid receptors in the brain stop responding to it and its effects plateau. Because buprenorphine also has a long half-life, it stays attached to these receptors for a long time, preventing the feeling in the patient of peaks followed by periods of withdrawal.