Excess mortality among opioid-using patients treated with oral naltrexone in Australia

Abstract

Introduction and aims: To estimate the number of deaths that would have occurred among patients receiving oral naltrexone for opioid use under the Special Access Scheme if these patients had received methadone.

Design and methods: We analysed mortality in cohorts treated with oral naltrexone and methadone. Data were from 1097 patients of in WA providing oral naltrexone for opioid use under the SAS,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.

Results: Oral naltrexone patients had higher mortality 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 (rate ratio 3.5; 95% confidence interval 2.2-5.8) and NSW (rate ratio 3.5; 95% confidence interval 2.4-5.0). Among 1097 oral naltrexone patients we 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.

Discussion and conclusions: 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.

Keywords: mortality; naltrexone; opioid dependence; opioid substitution therapy; treatment.