About Belmont Comprehensive Treatment Center in Portland, OR Belmont Comprehensive Treatment Center, located in Portland, Oregon, provides medication-assisted treatment (MAT) to adults age 18 and older of all genders who are struggling with opioid addiction. Our Portland center offers multiple medications as part of medication-assisted treatment, including naltrexone, methadone, buprenorphine, and Suboxone. Some methadone clinics provide only one type of medication to help lessen the effects of withdrawal and eliminate opioid cravings.