California Researchers Say Medicinal Marijuana Relieves Pain

By Christin Melton
Published: Tuesday, May 18, 2010
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In the last issue of Oncology & Biotech News, we reported concerns some clinicians have about using marijuana for medical purposes. A persistent concern has been the lack of clinical trials demonstrating marijuana’s effectiveness in any of the conditions for which it is legally prescribed in many states. Now, a team of researchers from the University of California San Diego School of Medicine’s Center for Medicinal Cannabis Research (CMCR) has presented a summary of studies to the California legislature that claims smoking marijuana relieves pain in several chronic illnesses.

CMCR was commissioned in 2000 with a grant of $8.9 million from the California state legislature. It has funded 15 studies on cannabinoids in an effort to determine which forms of marijuana, if any, have therapeutic value. Of the 7 clinical trials CMCR has sponsored, 6 have published results in peerreviewed scientific journals and 2 expect to release final data in 2011.

CMCR has been looking at smo ked and non-smoked preparations of cannabis, such as vaporization, patches, suppositories, or alternative oral forms. CMCR says its research shows cannabis relieves neuropathic pain in patients with spinal cord injuries and diseases that affect the nervous system, such as HIV. Higher doses of marijuana were associated with greater pain relief, but even medium doses proved effective.

The trials were randomized and typically involved comparing marijuana cigarettes with placebo cigarettes that consisted of marijuana from which delta- 9-tetrahydrocannabinol (THC) had been removed. Pain was assessed using standard measures, and researchers evaluated THC blood concentrations to determine the relationship between dose and extent of pain relief. Three trials enrolled patients who were no longer receiving sufficient pain relief from commonly prescribed medications.

CMCR has also been investigating whether smoking marijuana is effective at reducing spasticity and its associated pain in patients with multiple sclerosis. The Center says, “Results to date have found a significant improvement in both an objective measure of spasticity and pain intensity in patients whose standard therapy had provided inadequate relief.” Other studies sponsored by CMCR have looked at the effects of marijuana on sleep, driving, and fear. One investigated the mechanism of marijuana’s analgesic effects.

In a press statement, Igor Grant, MD, executive vice chair of the Department of Psychiatry at the UCSD School of Medicine and director for CMCR, said, “These findings provide a strong, science-based context in which policy makers and the public can begin discussing the place of cannabis in medical care.”

Some medical experts criticized the conclusions in the CMCR report and the studies, which they said were too short and too small to draw meaningful conclusions. Most of the studies had fewer than 20 participants, and some involved as few as 3 treatment sessions. In addition, the patients were not required to discontinue their current pain medications while participating in the study.

Grant stands by the CMCR findings. He told the Los Angeles Times the data demonstrate marijuana “is not a drug without value” and should no longer be designated a Schedule I drug. In a statement, CMCR said more investigation is needed, including efforts to determine marijuana’s mechanism of action and long-term effects. CMCR is not likely to be conducting those studies, however, having nearly exhausted its initial grant and with little hope of receiving another from cash-strapped California. With a growing number of states considering legalization of medicinal marijuana, CMCR suggested it is time for the federal government to stop giving the cold shoulder to medicinal marijuana research. You can read the full report from the CMCR at

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