I've heard that buprenorphine is a new medication for heroin addiction. What is it and how does it work?
Buprenorphine is an opioid medication, because it binds (attaches to) opioid receptors, but it has some unique properties that distinguish it from other opioids. It was originally approved in the United States as an analgesic (pain medication) in an injectable liquid form, but it was not widely used for pain, despite its efficacy as an analgesic. Its special properties make it ideal for treating addiction to opioids.
The medication is a partial agonist (activator) of opioids receptors, which means that it acts like an opioid when it binds the opioid receptor, but every molecule of the medication that attaches to an opioid receptor only partly activates that opioid receptor. A good analogy for this would be to imagine that the binding of heroin and other prescription opioids to the receptor is like a standard light switch, either on when the opioid molecule binds the receptor or off when it doesn't. In this analogy, buprenorphine binding to the receptor would be like a light switch with a dimmer that can only go to 60% brightness when the buprenorphine molecule binds the receptor. This property of buprenorphine minimizes the degree of opioid "high" one could feel on buprenorphine. The "high" potential is further limited because the medication is taken under the tongue and allowed to dissolve slowly, which reduces the rapidity of drug effect and makes it essentially impossible to get "high" on the medication, when used properly. Fortunately, the medication is sufficiently effective at opioid receptors that it will prevent and even reverse opioid withdrawal.
Another important pharmacologic property of buprenorphine is that the medication binds more strongly to the opioid receptor than other opioids. This makes it very difficult for someone to use another opioid and experience any effect from it while taking buprenorphine, because the buprenorphine molecules sit on the receptor and block other opioids from binding. A third property is that it stays on the receptor a long time, making it a long-acting medication, which can be taken daily, or even every second or third day (though most patients prefer to take it daily). The long duration of action of the medication means that withdrawal will emerge less quickly and ultimately develop with less intensity if the medication is stopped suddenly.
Buprenorphine may be used to detoxify individuals from opioids. It is very effective for this purpose, usually allowing for a very comfortable process. It can be somewhat difficult to begin the medication, because if a person starts it before they are in opioid withdrawal, the partial activation (agonist) effect of the medication may actually bring on the discomfort of withdrawal. Buprenorphine can also be used for short- or long-term maintenance treatment, because, when taken regularly, it eliminates the two main reasons people abuse opioids: to get high and to avoid withdrawal pain/discomfort. Research has shown that individuals who take buprenorphine regularly for the intermediate to long term are significantly less likely to relapse to opioid abuse than those who use it only for a brief detoxification and then attempt immediately to live drug-free.