Chronic pain relief from cannabis31st August 2010
Nerve-damaged patients who smoke small amounts of cannabis through a pipe can reduce chronic pain to a significant degree, a Canadian study has found.
Cannabis, which has been used as a form of pain relief for thousands of years, was also linked to improved sleep and anxiety levels.
Researchers studied a small group of 23 people in what they said was the first clinical outpatient trial involving smoked cannabis, although research into the effects of cannabis-based compounds, or cannabinoids, in pill form is currently under way.
They said further studies with more participants using special inhaler devices were needed.
Chronic neuropathic pain, caused by problems with signals passing across synaptic junctions, affects 1-2% of the population. There is currently little available to treat it.
While the pain relief seen in the study was small, UK-based experts said it was an important result nonetheless.
Writing in the Canadian Medical Association Journal, researchers said they wanted to investigate claims by some patients with nervous pain that smoking cannabis helped alleviate it.
Led by Mark Ware, the research team from McGill University in Montreal used three different potencies of cannabis - containing 2.5%, 6% and 9.4% of the active ingredient tetrahydrocannabinol - as well as a placebo.
Participants inhaled a single 25 mg dose of cannabis in varying strengths, or a placebo, under nurse supervision over a five-day period, three times a day.
This was followed by nine days off, then by another five-day dose period, four times over.
The group which received the strongest cannabis report a significant pain reduction, coupled with improved mood and better sleep, compared with the effects reported by the placebo group.
Ware called for further, longer-term studies using higher potencies of cannabis. Inhaler-type devices for delivering measured amounts of cannabis should also be trialled, he said.
London-based pain expert Tony Dickenson said a lot of patients with this type of pain say they benefit from cannabis, but said self-medicating could lead to health problems.
He said that even limited pain relief could make life easier for patients who experienced sleeplessness and depression because of their condition.
He said further studies should look at the appropriateness of cannabis for older people, and how taking the herb orally compared with inhaling it.
Peter Shortland, a senior lecturer in neuroscience at Barts and The London School of Medicine and Dentistry said that the cannabis used for the study did not produce the psychoactive effects that the full-strength herb was known for when used recreationally.
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