Cannabis for pain relief
Clinical bottom line
Cannabinoid derivatives tested in cancer, chronic non-malignant or acute pain proved no better than the least effective analgesics, but with many adverse events, including psychotropic adverse events.
FA Campbell, MR Tramèr, D Carroll, DJM Reynolds, RA Moore, HJ McQuay. Are cannabinoids an effective and safe treatment option in the management of pain? A qualitative systematic review. British Medical Journal 2001 323: 13-16 ( http://www.bmj.com/cgi/content/full/323/7303/13 )
The search used a number of electronic databases to look for trials of cannabis or cannabinoids given by any route of administration with analgesic or placebo for acute, chronic, or chronic non-malignant, or cancer pain.
There were nine full publications of randomised trials where pain was measured. Two were in acute postoperative pain, two in chronic non-malignant pain, and five in cancer pain.
Two trials (72 patients) showed intramuscular levomantradol to be more effective than placebo. Adverse effects were common though mild.
Chronic non-malignant pain
Two trials in two patients (both N of 1 trials with one patient in each) tetrahydrocannabinol 5 or 10 mg was better than placebo and about equivalent to codeine 50 mg.
Five trials with 128 patients tetrahydrocannabinol was roughly equivalent to codeine 60 mg in one trial. An analogue was also found to be equivalent to codeine 60 mg. Higher doses of tertrahydrocannabinol produced many adverse effects. At lower doses adverse effects were still more frequent than with standard analgesics.
These trials were not exceptionally large, nor particularly well designed. They showed some analgesic efficacy for cannabinoids, but equivalent to analgesics which perform poorly. Codeine 60 mg, for instance, can barely be distinguished from placebo even in meta-analysis, where the NNT is about 16. Other analgesics have NNTs of 2. Given that this comes with higher rates of adverse effects, and that higher doses are ruled out by adverse effects, cannabinoids are unlikely to have any useful place in analgesia in their present formulations.