Extended observation of reduced methamphetamine use with combined naltrexone plus bupropion in the ADAPT-2 trial

A 12-week placebo-controlled, sequential parallel Accelerated Development of Additive Pharmacotherapy Treatment for Methamphetamine Use Disorder (ADAPT-2) trial evaluated the effects of extended-release injectable naltrexone plus extended-release oral bupropion (NTX + BUPN) on methamphetamine (MA) use over two stages. This study reports on the previously unpublished stage 2 MA use in participants randomized at stage 1 to receive NTX + BUPN through both stages compared with those assigned to placebo.

This is a secondary analysis of the US National Institute on Drug Abuse (NIDA) ADAPT-2 network trial.

The parent ADAPT-2 trial was carried out across multiple NIDA Clinical Trials Network (CTN) sites in the United States.

This analysis includes 403 people with MA use disorder who participated in the ADAPT-2 CTN trial.

NTX + BUPN was compared with placebo over the course of the trial.

MA use was measured by urine drug screens conducted twice weekly for 12 weeks, then once in week 13 and once in week 16 post-treatment follow-up.

Participants on NTX + BUPN in stage 1 showed an additional 9.2% increase [95% confidence interval (CI), 0.09%-17.9%, P = 0.038] during stage 2 in their probability of testing negative for MA, with a total increase of 27.1% (95% CI, 13.2%-41.1%, P < 0.001) over the full 12 weeks of treatment. In contrast, participants on placebo in both stages increased in probability of testing MA-negative by a total of 11.4% (95% CI, 4.1%-18.6%, P = 0.002) over all 12 weeks. The 12-week increase among participants on NTX + BUPN was significantly greater-by 15.8% (95% CI, 4.5%-27.0%, P = 0.006)-than the increase among those on placebo.

For people with methamphetamine (MA) use disorder receiving treatment with extended-release injectable naltrexone plus extended-release oral bupropion (NTX + BUPN), continued treatment with NTX + BUPN after 6 weeks is associated with additional reductions in MA use up to 12 weeks.