Marijuana Eases Chronic Pain, Researchers Say

Aug. 30, 2010— -- Smoking marijuana modestly reduced pain and other symptoms of chronic neuropathic pain, results of a small trial showed.

The most potent dose used reduced average daily pain scores by 0.7 points on an 11-point scale, according to Mark A. Ware of McGill University in Montreal, Canada and colleagues.

Those who smoked weed with 9.4 percent of the active ingredient tetrahydrocannabinol (THC) also reported sleeping better, the researchers reported online in CMAJ.

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These results are important in light of the fact that patients who hear about pain relief from ongoing publicity about medical marijuana have had only a "trickle" of evidence to prove it, explained Henry J. McQuay of Oxford University in an accompanying editorial.

"If medical cannabis is not available where a patient lives, then obtaining it will take the patient outside of the law, often for the first time in his or her life," he wrote. "Good evidence would at least buttress that decision."

These quality results along with three other trials of smoked cannabis for neuropathic pain do support an analgesic effect that, "though not great, may be of use to some patients," McQuay concluded.

This study does offer hope since few drugs have proven effective in these patients, commented Dr. Steven P. Cohen, who as director of pain research at Walter Reed Army Medical Center in Washington, D.C., sees chronic pain in most of his patients with major war injuries.

However, the magnitude of the pain relief from smoking marijuana was less than expected compared with those few effective drugs, Cohen noted in an e-mail to MedPage Today and ABC News.

"When considered in the context of the higher incidence of minor and serious side effects with medical marijuana, cannabinoids should remain a third- or fourth-line drug for neuropathic pain," he wrote.

A bigger concern remains the "delivery system," which is substantially worse than tobacco cigarettes due to prolonged exposure to marijuana smoke from holding it in the lungs, commented Dr. Timothy A. Collins of Duke University's Pain and Palliative Care Clinic in Durham, N.C.