But for people with what's called opioid use disorder—which often starts with an opioid pain medication prescription —physicians often swap in another opioid medication, such as methadone, as well as partial and full opioid antagonists like buprenorphine and naltrexone, which bind to the same receptors that opioids do but instead of activating them, they block those receptors from being activated. According to the National Institute on Drug Abuse (NIDA), about 21 to 29 percent of people who are prescribed opioids for chronic pain end up using them in a way that wasn't intended by their prescribing doctors. According to a 2016 review by the New England Journal of Medicine, 79.5 percent of people who recently started using heroin had used prescription opioids in a way unintended by physicians prior to their use of heroin. To treat the opioid use disorder, doctors prescribe these alternative drugs (methadone, buprenorphine, naltrexone) and then gradually taper their patients off them with the hope that the body will continue to adjust. These opioid alternatives tend to be less potent than either opioids typically prescribed for pain or ones commonly used recreationally, like heroin. For example, Buprenorphine is what's known as an opioid partial agonist; its addictive side effects are similar to other opioids, but it's far less dangerous overall. And at low tapering doses, it's far less likely to initiate withdrawal symptoms than a gradual taper of a full opioid agonist.