Patients treated with naltrexone more likely to die than those on methadone
The issue: Oral naltrexone, and naltrexone implants, have been used in the treatment of opioid dependence in Australia the under provisions of the Special Access Scheme (SAS) of the Therapeutic Goods Act (1989), as oral naltrexone was unregistered prior to 2000 and naltrexone implants remain unregistered. While we know that mortality risk is halved among opioid users receiving methadone treatment, we do not know what the comparative impact on mortality is for patients treated with naltrexone.
What we did: Researchers analysed mortality in cohorts treated with oral naltrexone and methadone. Data were from 1097 patients in Western Australia (WA) provided oral naltrexone for opioid use under the SAS during 1998–2000, and all participants in WA (n = 2520) and New South Wales (NSW) (n = 11,174) methadone programs over the same period. We calculated mortality rates among patients receiving naltrexone and methadone, and excess mortality among patients receiving naltrexone.
What we found: Oral naltrexone patients were more likely to die than those treated with methadone, even when favourable assumptions were made about the effects of naltrexone on mortality. Total oral naltrexone mortality was significantly greater than for methadone in WA. Among 1097 oral naltrexone patients researchers estimate that there were 25–29 deaths over two years that would probably not have occurred if these patients had received methadone. The major reason was higher mortality rate post-treatment cessation.
Implications: Large-scale use of oral naltrexone to treat opioid users may not have, as intended, saved lives. Implant naltrexone continues to be prescribed under the SAS in the absence of reliable efficacy and safety data. There is a need to review widespread use of unregistered medications under the SAS, particularly with vulnerable patient groups.
Image credit: Benjamin Ellis.