Bisaga 2018: naltrexone-based detox to start Vivitrol didn't beat placebo

What they tested

378 adults with opioid use disorder were randomly assigned to one of three 7-day outpatient plans: rising doses of oral naltrexone plus a 3-day buprenorphine taper; naltrexone plus a placebo taper; or placebo for both. Everyone got the same fixed set of other medicines for withdrawal symptoms and daily counselling.

On day 8, people who passed a naloxone challenge (a test dose to check that opioids were out of their system) got their first shot of extended-release naltrexone (XR-NTX, sold as Vivitrol).

What they found

Rates of switching to XR-NTX were similar in all three groups: 46.0% with naltrexone plus buprenorphine, 40.5% with naltrexone alone and 46.0% with placebo. The study did not meet its primary endpoint.

Side effects were reported by 32.5% of all patients. They were mild to moderate and consistent with opioid withdrawal.

A first, second and third injection were received by 44.4%, 29.9% and 22.5% of patients.

Compared with the placebo group, the naltrexone-plus-buprenorphine group had more opioid abstinence during the switch and lower withdrawal scores after the shot.

Limits

• Every group got the same withdrawal medicines and daily counselling, so the trial tests naltrexone and buprenorphine on top of that support, not on their own.
• The abstract doesn't report drug use after the injections, so it can't say how people did once on the shot.

What it means if you're considering naltrexone

This trial was larger than the 2017 Sullivan trial, which found a naltrexone-assisted detox got more people onto the shot than a buprenorphine taper. Here, with placebo as the comparison, the naltrexone part made no difference to how many people reached the shot: a structured outpatient program with standard withdrawal medicines did just as well.

Starting the naltrexone shot after opioid use remains hard. In every group, fewer than half reached the first injection, and fewer still stayed for a second and third.