Methadone and various formulations containing buprenorphine are treatment drugs used in medication-assisted treatment, usually referred to as MAT. These are the MAT drugs approved for treatment of opioid addiction (opioid painkillers, heroin, fentanyl). We will take a look at the minus side as well as the plus side of these opioid addition treatment drugs. Treatment with MAT drugs can be right for some people. But anyone choosing this treatment so they can leave addiction behind should be prepared for the minus side of MAT.