Introduction | Opioid Antagonists (Naloxone and Naltrexone) | Buprenorphine: Qualities of Methadone and Naltrexone | Conclusion | References
For the treatment of opioid dependence, agonist treatments with medications like methadone and levomethadyl acetate (LAAM) have had the most impact. These medications are full opiate agonists. They attach to opiate receptors and stimulate them. They are effective for the treatment of opiate dependence mainly because they reduce opiate craving, reduce opiate withdrawal symptoms, and confer tolerance to opiates, thus reducing the euphoric effects of abused opiates. However, there are other effective pharmacotherapies available for the treatment of opioid dependence that take advantage of different interactions between medications and opiate receptors. For instance, opiate antagonists like naloxone and naltrexone occupy opiate receptors but do not activate them; because naloxone and naltrexone have a high affinity for the opiate receptor, they can prevent agonists with a lower affinity, like heroin, from binding with the receptor and thus reduce the euphoric effects of abused opioids. Partial opiate agonists, such as buprenorphine, have also shown efficacy in the treatment of opioid dependence. Partial agonists occupy opiate receptors but activate them only in a limited way so that there is a ceiling to their agonist effects. Partial agonists may also block the occupation of receptors by full agonists with lesser affinity, thus blocking the euphoric effects of abused opiates. A partial agonist such as buprenorphine provides some opiate subjective effects and thus is more acceptable to most opiate-addicted persons than an antagonist such as naltrexone. In overall clinical outcome, buprenorphine is comparable to methadone for the majority of opiate-addicted individuals who do not require a high dose of opiate.