Naltrexone of little help in reducing arthritis-related pain

Treatment with low-dose naltrexone does not appear to reduce nociceptive pain among patients with arthritis, as reported in a small pilot study.

This randomized, double-blind, placebo-controlled, crossover clinical trial included 17 patients with osteoarthritis and six with inflammatory arthritis. These patients were randomly assigned to receive either low-dose naltrexone (4.5 mg) or placebo for 8 weeks. Afterwards, the patients in each group received the alternative treatment for another 8 weeks. Each patient served as his or her own comparator.

The primary endpoint was differences in pain interference during the low-dose naltrexone and placebo treatment periods. Pain interference was assessed using the Brief Pain Inventory (scale, 0–70). Secondary endpoints included changes in mean pain severity, fatigue, depression, and multiple domains of health-related quality of life. The painDETECT questionnaire categorized pain as follows: nociceptive, neuropathic, or mixed.

Many patients described their pain as nociceptive (n=9) or mixed (n=8) rather than neuropathic (n=3). In mixed-effect models, the difference in pain interference during low-dose naltrexone treatment vs during placebo treatment was small and nonsignificant (mean, −23 vs −22, respectively; p=0.90).

Likewise, there were no significant differences observed in pain severity, fatigue, depression, or health-related quality of life.

The present data do not support the use of low-dose naltrexone for reducing nociceptive pain due to arthritis. Furthermore, the number of included patients was too small to rule out modest benefit or to evaluate inflammatory or neuropathic pain.