In a double-blind, placebo-controlled clinical trial to assess the impact of smoked medical cannabis, or marijuana, on the neuropathic pain associated with HIV, researchers at the University of California, San Diego School of Medicine found that reported pain relief was greater with cannabis than with a placebo. The study, sponsored by the University of California Center for Medical Cannabis Research (CMCR) based at UC San Diego, will be published on line, August 6 in the journal Neuropsychopharmacology.
Led by Ronald J. Ellis, M.D., Ph.D., associate professor of neurosciences at UCSD School of Medicine, the study looked at 28 HIV patients with neuropathic pain not adequately controlled by other pain-relievers, including opiates. They took part in the controlled study as outpatients at the UCSD Medical Center. The proportion of subjects achieving pain reduction of 30 percent or more was greater for those smoking cannabis than those smoking the placebo.
"Neuropathy is a chronic and significant problem in HIV patients as there are few existing treatments that offer adequate pain management to sufferers," Ellis said."We found that smoked cannabis was generally well-tolerated and effective when added to the patient's existing pain medication, resulting in increased pain relief."
Each trial participant participated in five study phases over seven weeks. During two five-day phases, randomly selected participants smoked either cannabis or placebo cigarettes made from whole plant material with cannabinoids (the psychoactive compound found in marijuana) removed, both provided by the National Institute on Drug Abuse. Outcome was tested by standardized tests measuring analgesia (lessened pain sensation), improvement in function and relief of pain-associated emotional distress.
Using verbal descriptors of pain magnitude, cannabis was associated with an average reduction of pain intensity from 'strong' 'to mild-to-moderate' in cannabis smokers, according to Ellis. Also, cannabis was associated with a sizeable (46% versus 18% for placebo) proportion of patients reporting clinically meaningful pain relief.
The study's findings are consistent with and extend other recent research supporting the short-term efficacy of cannabis for neuropathic pain, also sponsored by the CMCR.
"This study adds to a growing body of evidence that indicates that cannabis is effective, in the short-term at least, in the management of neuropathic pain," commented Igor Grant, M.D., professor of psychiatry and director of the CMCR.