For the treatment of opioid dependence, agonist treatment with methadone and buprenorphine has had the greatest impact. These medications are agonists in that they have affinity for opiate receptors resulting in binding to the receptor and activating it. Agonists 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 additional opiates, such as heroin. Methadone is a full agonist, whereas buprenorphine is a partial opiate agonist. Partial agonists bind to opiate receptors but activate them only in a limited way so that there is a ceiling to their agonist effects. Partial agonists may also prevent 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 addicts than an antagonist that binds to opiate receptors without activating them, thus producing no opiate effects. In overall clinical outcome, buprenorphine is comparable with methadone for the majority of opiate addicts who do not require a high maintenance dosage of opioid.