Aug. 6, 2008 -- Smoking pot may help relieve pain in patients with HIV-related neuropathy, a form of nerve damage that leads to burning and tingling sensations, which can be hard to treat with traditional medications.

"Neuropathy is a chronic and significant problem in HIV patients as there are few existing treatments that offer adequate pain management," researcher Ronald J. Ellis, MD, PhD, associate professor of neurosciences at the University of California, San Diego School of Medicine, says in a news release.

Ellis and colleagues compared medical marijuana to a placebo (fake drug) in 28 patients with HIV-related neuropathic pain that was not adequately controlled by pain medications, including opioids.

The team randomly assigned each participant to smoke either medical marijuana (cannabis) or a cigarette that resembled marijuana but did not contain the drug's active chemical, THC. The National Institute on Drug Abuse supplied both products.

The participants smoked the material four times a day for five straight days, then abstained for two weeks, and then followed the same experiment again. Each person also continued to take prescribed painkillers during the trial.

Smoking the pot provided much greater pain relief than smoking the placebo. Forty-six percent of participants had clinically meaningful pain relief with pot compared to 18% with placebo. Pain relief varied from "strong" to "mild to moderate."

The researchers say that medical marijuana significantly reduces HIV-related neuropathic pain when added to the patient's already-prescribed pain management regimen and may be an "effective option for pain relief" in those whose pain is not controlled with current medications.

The findings, which appear online in the journal Neuropsychopharmacology, add to a growing body of evidence that shows that medical marijuana can be a potent painkiller for patients with neuropathy. However, the substance can have a negative impact on certain mental skills.

Ellis' team also warns that long-term smoking of cannabis can cause lung problems. Alternative delivery methods are approved in Great Britain and Canada and are being considered by the U.S., according to background information in the journal article.