Post-marketing surveillance of methadone and buprenorphine in the United States

Introduction. There have been recent increases in the use of methadone and buprenorphine in the United States. Methadone is increasingly being used for pain management, and buprenorphine use has expanded to include treatment for opioid addiction, leading to exposures of these drugs in new populations. There is a debate about the relative safety of these two drugs in routine outpatient medical use. Methods. Data from the Researched Abuse, Diversion and Addiction-Related Surveillance (RADARS^®) System Programs were used to analyze rates of abuse, misuse, and diversion using the Drug Diversion, Key Informant, Poison Center and Opioid Treatment Programs, 2003-2007. National rate and rate ratios were calculated using population and person-time exposed denominators. Detailed data are presented on severity of medical outcome and drug formulations. Results. Between 2003 and 2007, there were steady increases in the rates of abuse, misuse, and diversion of both methadone and buprenorphine. Rate ratios (per 100,000 population per quarter) of abuse, misuse, and diversion were consistently higher for methadone than buprenorphine. RADARS System poison centers received 7,476 calls for methadone and 1,117 calls for buprenorphine. After accounting for availability, there were higher rates of calls for methadone misuse, abuse, and diversion than buprenorphine in three of the four programs. The numbers of exposures requiring medical attention correspond to 46.8% and 25.8% of all calls, for methadone and buprenorphine, respectively. The most commonly diverted form of methadone was solid oral tablets (which are typically dispensed at pharmacies, not at opioid treatment programs), comprising 73% of cases. Conclusions. Buprenorphine appears to have a better safety profile than methadone during routine outpatient medical use. However, both medications have roles in the treatment of pain and opioid addiction, and further research into their respective benefits and risks should be conducted.