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Cannabis: limited therapeutic benefit

Only one orally administered cannabis derivative, THC, is effective in providing a little relief from some pains associated with multiple sclerosis, at the cost of sometimes serious neuropsychological effects.

Currently illegal in France, Indian hemp (Cannabis sativa) is a well-known plant that has been used for nearly 5000 years in China. Since the 1990s, there has been a renewed interest in the therapeutic use of cannabis derivatives.

Multiple sclerosis sufferers experience a lot of pain due to neurological damage or disabilities, for which conventional painkillers are disappointing. Some cannabis derivatives, in particular delta9-tetrahydrocannabinol (THC), seem to be more effective than placebo in relieving these pains.

For other types of neuralgia, post-operative pain and cancer-related pain, the efficacy of cannabis is dubious. In other situations, when opioid painkillers are ineffective or poorly tolerated, evaluation has not been not sufficient to determine to what extent a cannabis derivative would be an effective alternative for some patients.

Cannabis derivatives have unpleasant adverse effects, especially neuropsychological, such as drowsiness and giddiness, and some patients experience withdrawal symptoms on stopping the treatment.

In practice, the role of cannabis in medicine is confined to the use of orally administered delta9-tetrahydrocannabinol as an analgesic for multiple sclerosis, if the patient can cope with its neuropsychological effects.

©Prescrire October 2009
 
"Cannabis derivatives and pain" Prescrire Int 2009; 18 (103):226 (pdf, subscribers only)
 
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