Temgesic sublingual tablets contain the active ingredient buprenorphine, which is a type of medicine called an opioid analgesic (painkiller). It is a strong painkiller related to morphine. Opioid painkillers work by mimicking the action of naturally occurring pain-reducing chemicals called endorphins. Endorphins are found in the brain and spinal cord and reduce pain by combining with opioid receptors. Buprenorphine is used to relieve moderate to severe pain, for example pain due to cancer or a heart attack. However, it is used less frequently than other opioid painkillers because it can also oppose the effects of other opioid painkillers that may be given at the same time. This is because in addition to stimulating opioid receptors, buprenorphine can also block them and thus prevent other opioids from acting on them. In people who are dependent on opioids, this can cause withdrawal symptoms and an increase in pain.