Cannabis-based drug shows efficacy against RA pain

No drug-treated patients withdrew from the study due to adverse events.

A randomized, double-blind study found that a cannabis-based drug significantly reduced pain in patients with rheumatoid arthritis.

David R. Blake, FRCP, a professor of bone and joint medicine at the Royal National Hospital for Rheumatic Diseases in Bath, England, and colleagues at several U.K. centers, evaluated the effectiveness of the cannabis-based drug Sativex (GW Pharmaceuticals) on rheumatoid arthritis (RA) pain over five weeks.

Sativex is an oromucosal spray that contains 2.7 mg of delta-9-tetrahydrocannabinol (THC) and 2.5 mg of cannabidol (CBD). Mouse studies have shown that THC and CBD have anti-inflammatory effects, and that CBD can block the progression of RA, leading to symptom improvements. However, this is the first controlled study of a cannabis-based drug in RA patients, according to a press release announcing the results.

The study included data for 54 patients who completed follow-up; 30 patients randomly assigned to Sativex treatment and 24 who received placebo. The researchers allowed patients to administer up to six doses of the drug per day, beginning with a single dose 30 minutes before retiring. Patients could then increase by one dose every two days over two weeks based on their individual response. Stable dosing was then maintained for the remaining three weeks, according to the study.

All drug dosing was limited to the evening to minimize possible intoxication-type reactions, the authors noted in the study.

The researchers found that Sativex-treated patients had statistically significant improvements in pain. Using a scale from 0 (no pain) to 10, pain on movement decreased in Sativex-treated patients from a mean baseline score of 7 to 4.8 at five weeks’ follow-up (P=.044). In comparison, average pain on movement in placebo patients decreased from a mean baseline score of 6.7 to 5.3 at five weeks.

Pain at rest scores decreased from a baseline mean of 5.3 to 3.1 at five weeks in Sativex-treated patients and from 5.3 to 4.1 for placebo-treated patients (P=.018). Average scores for quality of sleep decreased from 5.7 at baseline to 3.4 for Sativex-treated patients and from 5.8 to 4.6 for placebo patients (P=.027), according to the study.

Mean 28-joint disease activity scores (DAS28) also decreased for Sativex-treated patients, dropping from 5.9 at baseline to 5 at five weeks follow-up (P=.002). For placebo patients, mean DAS28 scores decreased only 0.1 point from 6 at baseline.

Average pain intensity, measured using the Short-Form McGill Pain Questionnaire (SF-MPQ), improved 15 points in Sativex patients, from 48 at baseline to 33 at final follow-up, but remained unchanged at 50 for placebo-treated patients, according to the study.

Adverse events were mainly mild or moderate, and included dizziness, light-headedness, dry mouth and nausea. Eight patients experienced mild dizziness, which occurred during the initial two weeks of the study for four patients as they gradually increased doses. Another two patients experienced dizziness two days after the initial two-week period. The researchers believe this was probably due to patients getting used to the correct drug dose.

Three placebo patients but no Sativex-treated patients withdrew from the study due to adverse events, the authors noted.

If further trials are initiated, researchers expect to extend dosing over a full 24 hours, according to the press release.

“The beneficial effects in this study occurred in the context of a dosing regime restricted to evening dosing ... . However, 24-hour dosing with Sativex ... in trials for multiple sclerosis resulted in only minimal intoxication scores,” Philip Robson, FRCPsych, senior research fellow and consultant psychiatrist at the Oxford University Department of Psychiatry and director of the Cannabinoid Research Institute within GW Pharmaceuticals, said in the release.

For more information:
Blake DR, Robson P, Ho M, et al. Preliminary assessment of the efficacy, tolerability and safety of a cannabis-based medicine (Sativex) in the treatment of pain caused by rheumatoid arthritis. Rheumatology. Published online ahead of print and accessed November 9, 2005. Available at http://rheumatology.oxfordjournals.org/cgi/content/abstract/kei183v1.