Opioid Agonists and Partial Agonists (Maintenance Medications)
Studies show that people with opioid use disorder who follow detoxification with complete abstinence are very likely to relapse, or return to using the drug.10 While relapse is a normal step on the path to recovery, it can also be life threatening, raising the risk for a fatal overdose.11 Thus, an important way to support recovery from heroin or prescription opioid use disorder is to maintain abstinence from those drugs. Someone in recovery can also use medications that reduce the negative effects of withdrawal and cravings without producing the euphoria that the original drug of abuse caused. For example, the FDA recently approved lofexidine, a non-opioid medicine designed to reduce opioid withdrawal symptoms. Methadone and buprenorphine are other medications approved for this purpose.
Methadone is a synthetic opioid agonist that eliminates withdrawal symptoms and relieves drug cravings by acting on opioid receptors in the brain—the same receptors that other opioids such as heroin, morphine, and opioid pain medications activate. Although it occupies and activates these opioid receptors, it does so more slowly than other opioids and, in an opioid-dependent person, treatment doses do not produce euphoria. It has been used successfully for more than 40 years to treat opioid use disorder and must be dispensed through specialized opioid treatment programs.12
Buprenorphine is a partial opioid agonist, meaning that it binds to those same opioid receptors but activates them less strongly than full agonists do. Like methadone, it can reduce cravings and withdrawal symptoms in a person with an opioid use disorder without producing euphoria, and patients tend to tolerate it well. Research has found buprenorphine to be similarly effective as methadone for treating opioid use disorders, as long as it is given at a sufficient dose and for sufficient duration.13 The U.S. Food and Drug Administration (FDA) approved buprenorphine in 2002, making it the first medication eligible to be prescribed by certified physicians through the Drug Addiction Treatment Act. This approval eliminates the need to visit specialized treatment clinics, thereby expanding access to treatment for many who need it. Additionally, the Comprehensive Addiction and Recovery Act (CARA), which was signed into law in July 2016, temporarily expands eligibility to prescribe buprenorphine-based drugs for medication-assisted treatment (MAT) to qualifying nurse practitioners and physician assistants through October 1, 2021. Buprenorphine has been available for opioid use disorders since 2002 as a tablet and since 2010 as a sublingual film.14 The FDA approved a 6-month subdermal buprenorphine implant in May 2016 and a once-monthly buprenorphine injection in November 2017. These formulations are available to patients stabilized on buprenorphine and will eliminate the treatment barrier of daily dosing for these patients. (Also see "What are misconceptions about maintenance treatment?")
Naltrexone is an opioid antagonist, which means that it works by blocking the activation of opioid receptors. Instead of controlling withdrawal and cravings, it treats opioid use disorder by preventing any opioid drug from producing rewarding effects such as euphoria. Its use for ongoing opioid use disorder treatment has been somewhat limited because of poor adherence and tolerability by patients. However, in 2010, an injectable, long-acting form of naltrexone (Vivitrol®), originally approved for treating alcohol use disorder, was FDA-approved for treating opioid use disorder. Because its effects last for weeks, Vivitrol® is a good option for patients who do not have ready access to health care or who struggle with taking their medications regularly.
Because each medication works differently, a treatment provider should decide on the optimal medication in consultation with the individual patient and should consider the patient’s unique history and circumstances.