Minozzi 2011 (Cochrane): daily naltrexone pills for opioid dependence

What they tested

Three reviewers looked for randomized trials comparing naltrexone maintenance, meaning taking the pill regularly over time, with placebo or other treatments after opioid detox. They searched databases up to June 2010, checked reference lists and contacted drug companies and researchers. Thirteen trials with 1,158 participants qualified.

Comparisons included placebo or no medicine, psychotherapy, benzodiazepines and buprenorphine. The question was whether the pills prevented relapse to opioids.

What they found

Against placebo or no medicine, naltrexone pills made no statistically significant difference on any of the main outcomes.

In studies where people were forced to take the pills, naltrexone came out ahead on staying in treatment and abstinence (risk ratio 2.93).

The results section reports one outcome in naltrexone's favor: fewer people going back to prison (risk ratio 0.47), from only two studies. The authors' conclusions describe that same outcome as no better than placebo, so it's best read with caution.

Naltrexone was no better than psychotherapy, benzodiazepines or buprenorphine, but each of those comparisons came from a single study. Only 28% of people in the included studies stayed in treatment.

The authors concluded that the trials so far did not allow a proper evaluation of oral naltrexone for opioid dependence, and that it can't yet be considered proven better than other treatments.

Limits

• Few people stayed in treatment (28%), so it's hard to separate whether the drug failed or people simply stopped taking it. The authors note that naltrexone works as a drug, but adherence and retention are poor.
• Several comparisons rested on one or two studies.
• It covers daily pills only, not the monthly shot or implants.

What it means if you're considering naltrexone

For opioid use disorder, this review is the main reason daily naltrexone pills are seen as a weak option on their own: they helped when people were made to take them, but most people in these trials didn't stay on them. The site's guides note that the monthly shot has stronger trial results and is generally recommended instead of pills for opioids.

The review is about opioids. Naltrexone pills for alcohol have their own, separate evidence.