Sullivan 2017: two ways to start the Vivitrol shot after opioids

What they tested

Naltrexone can set off sudden withdrawal in someone who still has opioids in their system, so people with opioid dependence have to get through detox before the extended-release naltrexone shot (XR-naltrexone, sold as Vivitrol). This trial randomly assigned 150 adults, two to one, to one of two outpatient detox plans.

Naltrexone-assisted detox lasted 7 days: a single day of buprenorphine, then rising doses of oral naltrexone, with clonidine and other non-opioid medicines for symptoms. Buprenorphine-assisted detox was a 7-day buprenorphine taper followed by a week-long wait before the shot, as the official prescribing information advises.

Both groups got behavioral therapy focused on taking the medicine, and a second shot.

What they found

56.1% of the naltrexone-assisted group were successfully started on XR-naltrexone, compared with 32.7% of the buprenorphine-assisted group, a significant difference.

50.0% vs 26.9% received the second injection at week 5. Both results held after adjusting for the main type of opioid used, how it was taken and the amount used at the start.

The authors concluded that low-dose naltrexone with a single day of buprenorphine and non-opioid medicines was safe and well tolerated as a way to start the shot. Even with this method, many people did not make it to the first injection.

Limits

• The abstract reports only whether people started the shot and got the second one, not how they did after week 5.
• The buprenorphine plan included a week-long wait after the taper, so the trial compares two whole approaches, not just the medicines used.
• Both plans came with extra medicines and behavioral therapy, so results may differ in clinics that can't offer that support.

What it means if you're considering naltrexone

For someone with opioid use disorder who wants the naltrexone shot, getting through detox to the first injection is often the hardest step. This trial suggests a shorter, naltrexone-based outpatient detox got more people there than the standard buprenorphine taper and wait.

A larger 2018 trial by Bisaga and colleagues found similar rates across three schedules, one of them placebo, so the benefit of the naltrexone-based schedule itself is less clear than this trial alone suggests.