Los Angeles Times - October 6, 2003
Jane E. Allen, Times Staff Writer

German researchers now have found that a synthetic version of one of many marijuana compounds safely reduced chronic nerve pain without impairing thinking and behavior. If the preliminary findings hold up in larger trials, capsules containing this compound might one day be prescribed for hard-to-treat pain.

The principal active ingredient in cannabis is tetrahydrocannabinol, or THC. That compound has been the most studied, but researchers around the world are also looking more closely at the plant's other chemical compounds for potential health benefits. Scores of them belong to a group called cannabinoids; others include flavonoids, which are thought to have antioxidant properties.

"It's not a surprise that these cannabinoids have medical benefit," said Dr. Donald I. Abrams, an AIDS specialist conducting clinical trials of marijuana at San Francisco General Hospital.

People with cancer, AIDS and other chronic diseases have long attested to the plant's ability to provide relief from nausea and pain. "That's why we're investigating marijuana," Abrams said.

Previous studies have shown some cannabinoids have limited ability to blunt acute nerve pain, typically associated with an injury. But the German study found that a cannabinoid called CT-3 could help sufferers of chronic neuropathy, who often don't respond to standard medications.

CT-3 is related to THC. But the problem with THC is that even at low doses, it can impair thinking and coordination, and create anxiety, panic attacks, psychosis and paranoia, as well as dry mouth, blurred vision, and a drop in blood pressure upon standing.

Despite these effects, scientists have remained interested in cannabinoids, because the body has natural cannabinoid receptors that offer potential drug targets.

CT-3 first showed promise in animals as an anti-inflammatory and as a reliever of two aspects of neuropathy: pain and extreme sensitivity to ordinary sensations.

Researchers at Hannover Medical School in Germany, working with an American colleague, gave various doses of CT-3 to 24 volunteer patients with chronic neuropathic pain in places such as the foot, arm, face and head. Many patients also were taking other pain-relieving medications such as narcotics, muscle relaxants, antidepressants and sedatives.

The researchers found that CT-3 was more effective than a placebo at relieving pain; its effects were greatest with milder pain. Increasing the dose brought no greater relief. The major side effects were dry mouth and fatigue.

"What's promising is that there can be a product that stimulates the cannabinoid receptors and does not have the emotional and hallucinatory effects otherwise known for THC," said Dr. Joel Saper, a neurologist who directs the Michigan Head-Pain and Neurological Institute in Ann Arbor. He'd like to see longer CT-3 studies using larger numbers of patients who aren't taking other pain medications: "We need to see how this would work in patients not on all these drugs."

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