Marijuana Reduces HIV Neuropathy

SAN FRANCISCO, Feb. 12 -- Smoking marijuana significantly reduces nerve pain associated with HIV infection, according to researchers here.

In a randomized, placebo-controlled trial, the drug reduced chronic neuropathic pain by 34% compared with 17% for patients smoking placebo cigarettes, found Donald Abrams, M.D, of the University of California San Francisco.

The pain reductions are comparable with those seen with oral drugs used to treat peripheral HIV-associated neuropathy, Dr. Abrams and colleagues reported in the Feb. 13 issue of Neurology.

"There is a measurable medical benefit to smoking cannabis for these patients," Dr. Abrams commented.

In the study, 50 patients with HIV-associated neuropathy were randomly assigned to smoke either cannabis or placebo cigarettes three times a day for five days under supervision as in-patients San Francisco General Hospital.

The cigarettes, supplied by the National Center on Drug Abuse, were identical in appearance, but the placebo cigarettes had the active ingredient -- delta-9-tetrahydrocannabinol - removed.

To be eligible for the study, patients had to have an average daily pain score of at least 30 on a 100-point visual analog scale. The primary outcome was change in the daily pain score, while secondary outcomes included acute pain before and after the first cigarette of the five-day session and again before and after the last cigarette of the session.

A subset of patients also took part in an acute pain experiment in which they were subjected to heat or to other painful stimuli, the researchers reported.

The investigators found:

• Over the course of the study, smoked cannabis reduced daily pain by 34%, versus 17% with placebo, a difference that was statistically significant at P=0.03.
• 52% of the cannabis group reported at least a 30% reduction in pain, compared with 24% in the placebo group, which was significant at P=0.04.
• The first cannabis cigarette reduced chronic pain, on average, by 72%, compared with 15% for placebo, which was significant at P<0.001.
• On Day five, before smoking the last cigarette, median pain ratings were significantly lower among the cannabis patients (at P=0.006) and were further reduced by 51% versus 5% after smoking. The reduction was significant at P<0.001.
• Cannabis also reduced experimentally induced hyperalgesia to both brush and von Frey hair stimuli (P?0.05) but had little effect on the painfulness of heat stimulation.
• No serious adverse events were reported.

In general, Dr. Abrams and colleagues found, adverse events such as sedation, dizziness, and confusion were significantly higher among the cannabis smokers.

However, in both groups, the values "hovered closer to zero than one and do not represent any serious safety concerns," the researchers said.

Also, there was little difference in mood effects between the two groups, Dr. Abrams and colleagues said, a finding that argues against the idea that cannabis smokers didn't feel pain because of the high associated with the drug.

The study indicates that "cannabis may indeed be useful in the amelioration of a very distressing, disabling, and difficult-to-treat complication of HIV," said Igor Grant, M.D., of the University of California at San Diego School of Medicine, and director of the University of California Center for Medical Cannabis Research, which was a sponsor of the study.