There is "no sound evidence" for clinicians to recommend that patients with rheumatic diseases take cannabinoid treatments, according to a review published online November 9 in Arthritis Care & Research. However, the authors suggest there is merit to further research on cannabinoids' effect on pain and sleep in these conditions.
A systematic review of research since 1940 uncovered few studies examining the effects of cannabinoids in rheumatic diseases, according to Mary-Ann Fitzcharles, MD, from the Division of Rheumatology and Alan Edwards Pain Management Unit, McGill University Health Centre, Quebec, Canada, and colleagues. "Amongst a vast array of rheumatic conditions, cannabinoid effects have only been studied in [rheumatoid arthritis], [fibromyalgia,] and [osteoarthritis], with the latter study prematurely terminated due to lack of efficacy," they write.
Moreover, the authors judged all of the studies included in the analysis as having a high risk of bias, and all had extremely low numbers of participants, suggesting "the possibility that results may be completely random."
Up to 10% of people in Canada suffering from chronic pain not caused by cancer use herbal cannabis to self-medicate, Dr Fitzcharles and colleagues write. In the body, the endocannabinoid system helps modulate pain and inflammation. Cannabinoids, as a group, include the body's natural regulatory molecules, phytocannabinoids derived from plants, and synthesized pharmaceutical preparations.
To carry out a systematic review mandated by the Canadian Rheumatology Association, a McGill University Health Centre librarian conducted a comprehensive literature search in September 2013 and updated the search in January 2015. The team found no randomized controlled trials that examined the effect of herbal cannabis, but they did identify four controlled studies that tested synthetic cannabinoids. Fifty-eight patients had rheumatoid arthritis, 71 patients had fibromyalgia, and 74 patients had OA.
The study that included patients with osteoarthritis was halted because of lack of effects; the three that were completed ran for 5 to 8 weeks.
Only one of the three studies compared placebo with the effects of phytocannabinoids extracted from cannabis, which were taken by patients with rheumatoid arthritis as an oromucosal spray. The 5-week trial included 58 patients with rheumatoid arthritis. Its selected measurements, however, were "not the usual standard for measurements of pain response or change in sleep," the authors say, and scant information was provided about rheumatoid arthritis disease, including duration and additional medicines taken by the patients. Of patients in the treatment group, 26% reported dizziness, 13% said they had dry mouth, 11% felt light-headed and nauseous, and 6% experienced falls.
The other two studies looked at the synthetic cannabinoid nabilone as a potential treatment for FM, with one 8-week trial enrolling 71 patients and one 6-week trial enrolling 31 patients. In the first FM trial, the treatment group's pain improvement was "significant" at 4 weeks, but almost half of those patients reported drowsiness. The second fibromyalgia trial compared sleep disturbance associated with from 0.5 to 1 mg/day of nabilone with that associated with from 10 to 20 mg/day of amitriptyline. Both treatments showed a positive effect on sleep, and there were no significant differences when it came to pain and quality of life.
"In view of the considerable limitations of the studies examined in this review, including small sample sizes, short duration, only modest efficacy and a high rate of mild to moderate adverse effects, it is not currently possible to recommend this category of treatments as therapy for patients with rheumatic diseases," Dr Fitzcharles and colleagues conclude. "Any conclusions based on these studies remain tenuous and call for larger, well controlled clinical trials to better understand potential benefits and risks as pertaining to rheumatic conditions."
The authors have disclosed no relevant financial relationships.
Arthritis Care Res. Published online November 9, 2015. Abstract
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