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Medical Marijuana Has Merit, Research Shows

Although Research Shows Medical Mariuana Works, Critics Say California Center's Research Is Flawed

By Kathleen Doheny
WebMD Health News

Reviewed By Louise Chang, MD

Feb. 18, 2010 -- Marijuana can be a promising treatment for some specific, pain-related medical conditions, according to California researchers who presented an update of their findings Wednesday to the California Legislature and also released them to the public.

"I think the evidence is getting better and better that marijuana, or the constituents of cannabis, are useful at least in the adjunctive treatment of neuropathy," Igor Grant, MD, executive vice-chairman of the department of psychiatry at the University of California San Diego School of Medicine and director of the Center for Medicinal Cannabis Research at the University of California, tells WebMD.

"We don't know if it's a front-line treatment. I'm hoping the results of our studies will prompt larger-scale studies that involve a much more varied population."

"This [report given to the Legislature] sets the stage of larger-scale studies," he says.

Some experts who reviewed the report say some of the studies are flawed and that they worry about the long-term health effects of marijuana smoke.

Perspective: Medical Marijuana Research

Some observers speculated that the researchers presented their report to the Legislature to call attention to marijuana research because an initiative to legalize marijuana for general use is expected to be on the California ballot in November 2010.

But Grant says that's not the case. "We sent it to the Legislature because our report was due," he says.

The program Grant directs was launched in 1999, when the California Legislature passed (and the governor signed) SB 847. Since then, the center has completed five scientific trials, with more in progress.

Medical Marijuana: The Research Scorecard

Five studies, published in peer-reviewed medical journals, show the value of marijuana for pain-related conditions, the researchers say in the report.

  • Smoked cannabis reduced pain in HIV patients. In one study, 50 patients assigned either to cannabis or placebo finished the study. Although 52% of those who smoked marijuana had a 30% or more reduction in pain intensity, just 24% of those in the placebo group did. The study is published in the journal Neurology. In another study, 28 HIV patients were assigned to either marijuana or placebo -- and 46% of pot smokers compared to 18% of the placebo group reported 30% or more pain relief. That study is in Neuropsychopharmacology.
  • Marijuana helped reduce pain in people suffering spinal cord injury and other conditions. In this study, 38 patients smoked either high-dose or low-dose marijuana; 32 finished all three sessions. Both doses reduced neuropathic pain from different causes. Results appear in the Journal of Pain.
  • Medium doses of marijuana can reduce pain perception, another study found. Fifteen healthy volunteers smoked a low, medium, or high dose of marijuana to see if it could counteract the pain produced by an injection of capsaicin, the "hot" ingredient in chili peppers. The higher the dose, the greater the pain relief. The study was published in Anesthesiology.
  • Vaporized marijuana can be safe, other research found. In this study, 14 volunteers were assigned to get low, medium, or high doses of pot, either smoked or by vaporization delivery, on six different occasions. The vaporized method was found safe; patients preferred it to smoking. The study is in Clinical Pharmacology & Therapeutics.

A sixth study, as yet unpublished, found marijuana better than placebo cigarettes in reducing the spasticity associated with multiple sclerosis and the pain associated with the spasticity.

Medical Marijuana Research: What's Next?

Grant's researchers will finish two more studies, with results expected by 2011, he says. What happens then, when the initial allocation of nearly $8.7 million, awarded back in 2000, runs out?

"We're going to act as a kind of shell or organizational structure to help investigators apply for funding with the NIH [and others]," he says. Grant says he is expecting no more funding from cash-strapped California.

Although 14 states have legalized medical marijuana, he says, California is the only state that has "stepped up to the plate" to do research.

Medical Marijuana Research: Other Opinions

The California center's studies are flawed, says Joel Hay, PhD, professor of pharmaceutical economics and policy at the University of Southern California, Los Angeles, and a vocal critic of medical marijuana.

"It's not medicine," he says of marijuana. "It would never be approved by the FDA.

"I certainly concede that cannabinoids may have a very valuable medical role," he says. But the danger is in the smoking of marijuana, he says, citing health effects.

Isolating the active ingredient is a better approach, he says, and has actually already been done. "If you want a cannabionoid, it's here," he says, referring to Marinol, available and FDA approved. The active ingredient is THC or tetrahydrocannabinol, the same as found in marijuana.

"Marijuana contains a huge variety of compounds, some of which have not even been thoroughly identified," Hay tells WebMD. The studies, he says, are all short-term, with small groups.

Another flaw, he says, is that it's difficult to have a true placebo when studying marijuana. "People know when they are consuming a psychoactive product," he says.

Another flaw is that patients were allowed to continue on their pain medicine, says Kevin Weissman, PharmD, director of drug information services at Los Angeles County+University of Southern California Medical Center. That may have affected the results.

Grant counters that it was not humane to take patients off pain medicines that were providing any degree of relief.

Like Hay, Weissman says marijuana does have an analgesic effect. But he worries about the long-term effect of marijuana smoke and says research is needed to find a safer delivery system that works, such as vaporization.

SOURCES: Igor Grant, MD, executive vice-chairman, department of psychiatry, University of California San Diego School of Medicine; director, Center for Medicinal Cannabis Research, University of California.

Kevin Weissman, PharmD, director of drug information services, Los Angeles County+University of Southern California Medical Center, Los Angeles.

Joel Hay PhD, professor of pharmaceutical economics and policy, University of Southern California, Los Angeles.

Abrams, D. Neurology, February 2007; vol 68: pp 515-521.

Abrams, D. Clinical Pharmacology and Therapeutics, November 2007; vol 82: pp 572-578.

Ellis, R. Neuropsychopharmacology, published online Aug. 6, 2008; vol 34: pp 672-680.

Wallace, M . Anesthesiology, November 2007; vol 107: pp 785-796.

Wilsey, B. Journal of Pain, April 2008; vol 9: pp 506-521.

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