TUESDAY, Feb. 13 (HealthDay News) -- Adding fuel to the debate over medical marijuana, a new study suggests that AIDS patients can relieve stubborn nerve pain in their feet by smoking the drug.

On average, patients reported a 34 percent improvement in foot pain after smoking pot, twice that of those smoking a weakened form of the drug.

The study is small, and the findings don't reveal why marijuana may reduce pain. Experts also noted that there's a potentially distracting side effect to the treatment -- getting high.

Still, the study findings add support to the idea that medical marijuana isn't "like some sort of Cheech and Chong show," said study lead author Dr. Donald I. Abrams, professor of clinical medicine at the University of California, San Francisco.

After all, he said, the study has been published in the Feb. 13 issue of Neurology, a respected medical journal.

The study has also re-ignited debate on the thorny issue of medical marijuana use. In a statement released Tuesday, a variety of national HIV/AIDS advocacy groups called for congressional hearings in response to the study findings.

"It's time for Washington to stop playing politics with patients' lives and advance this important scientific discovery," Steph Sherer, executive director of Americans for Safe Access, said in the statement. "The study is a wake-up call for Congress to hold hearings to investigate therapeutic use and encourage research."

For his part, UCSD's Abrams said he has studied the medical effects of marijuana for a decade. The new research examines its effects on AIDS patients with a condition called neuropathy, a painful burning numbness that can strike the feet and hands.

The condition, which can affect about a third of patients, is often difficult to treat, Abrams said, and painkillers often fail to ease the discomfort. In some cases, patients have to resort to anti-seizure medications.

According to Abrams, research had suggested that marijuana might be able to treat nerve pain. In the new study, his team first got approvals from various agencies and then launched a study using marijuana.

Fifty patients, mostly men, took part in the research. Half smoked marijuana three times daily for five days. The other half smoked a weakened form of marijuana. The patients were then asked to rank their pain on a scale of one to 10.

The patients who smoked the full-strength marijuana reported a 34 percent reduction in pain, compared to 17 percent among the other smokers. Half of the full-strength smokers reported more than a 30 percent reduction in pain, while just 24 percent of the placebo smokers did.

The side effects were minor, said Abrams, who noted that "most of these people smoked marijuana to begin with." All had smoked marijuana at least six times in their lives; the researchers wanted to make sure they were familiar with pot smoking and its effects.

The patients did get high, although Abrams said the marijuana was a weak type -- just 3.56 percent tetrahydrocannabinol, or THC, the active ingredient in pot. "We did measure their level of high, and it didn't seem to necessarily correlate with their pain relief."

Abrams discounted the possible risk of lung cancer for the marijuana smokers, saying some research has suggested that they actually have a lower risk than others. He added that researchers are looking into possible ways to vaporize marijuana, which could "deliver a similar amount of THC with less potential for toxicity."

According to Abrams, it's not clear how marijuana works to lower pain, but it may reduce inflammation. Other research has linked substances in marijuana to pain reduction.

David Murray, chief scientist at the White House Office of National Drug Control Policy, wasn't convinced by the study, which he said was small and didn't account for the possibility that the patients who got the placebo marijuana would know they weren't smoking the real thing.

He added that the drug poses risks for AIDS patients in particular, because their immune systems are compromised, and he questioned the risk of smoking a "combustible weed that has bacteria and fungus" in it.

While Murray acknowledged that cannabinoid-based medications have a "great deal of promise and potential," he said they need to be purified first. "Smoked, raw marijuana is not that avenue. It's a cul-de-sac, it's a dead end," he said.

But another expert had more praise for the study. Dr. Mark Wallace, professor of clinical anesthesiology and program director of the Center for Pain Medicine at the University of California, San Diego, applauded the study, saying it was well done. "There are very few studies of this kind looking at inhaled cannabis and pain, and they are difficult to conduct," he said. "The authors should be commended."

And what about the fact that patients get high when they smoke pot?

"Although subjects will report high levels of 'highness,' my studies showed little effect on cognition," Wallace said. "Other studies have shown little effect on motor tasks. Also, the pain relief does not seem to correlate with the feeling of highness, in that when subjects come down from the high, they continue to feel pain relief."

So, should AIDS patients with nerve pain begin smoking marijuana? Ask your doctor, Abrams advised.

Moe information

For more on AIDS-linked foot neuropathy, head to the San Francisco AIDS Foundation.