In Norway, naltrexone is approved as supportive treatment of alcohol dependence. The recommended dose is 50 mg, equivalent to the marketed tablet. Naltrexone in much lower doses than 50 mg has been used in Norway for the treatment of a variety of diseases, such as multiple sclerosis (MS), Crohn's disease, fibromyalgia, cancer, inflammatory bowel disease, chronic fatigue syndrome, and amyotrophic lateral sclerosis. Doses of 3 to 5 mg per day have often been termed low dose naltrexone. This use is beyond the approved indication. The purpose of this report is to examine whether there is a documented effect of the use of naltrexone in low doses.

We summarized data from a systematic review and several randomized controlled and prospective controlled studies in order to investigate the effect of using naltrexone in low doses on illness, and on functioning in daily life and to examine the risk of side effects.

We identified studies for people with:

• Crohn's disease (one systematic review, two studies)
• multiple sclerosis (two studies)
• fibromyalgia (two studies)
• cancer (one study)
• HIV (one study)
• various pain conditions (three studies)
• opioid dependence (six studies)

All studies were either small, of short duration, or had other methodological limitations. We considered the documentation to have very low quality. That means that we cannot conclude whether the use of naltrexone in low doses is effective or safe.