Inhaled cannabis shown effective for diabetic neuropathy pain

Researchers at the University of California San Diego conducted a randomized, double-blind study evaluating 16 subjects to assess the efficacy and tolerability of inhaled cannabis for treating pain caused by diabetic peripheral neuropathy (DPN). They studied the effects of low, medium and high doses of inhaled cannabis on DPN pain and hyperalgesia. Subjects participated in four outpatient treatment sessions, separated by two weeks, in which they were exposed to placebo or three different doses of aerosol 1% THC, the most abundant and psychoactive compound in cannabis. As a drug delivery method for marijuana research, inhalation is preferred because the pharmacokinetics of inhalation are superior to smoking, as peak effects occur quickly and are more easily titrated.

DPN occurs in half of diabetes patients and 15 percent have pain, especially in the feet. Many patients do not achieve satisfactory relief from two FDA-approved treatments. Animal research in models of neuropathic pain suggest that cannabinoids may be effective in reducing pain, but no studies have focused specifically on painful DPN.

"We hypothesized that inhaled cannabis would result in a dose-dependent reduction in spontaneous and evoked pain with a concomitant effect on cognitive function," said lead author Mark S. Wallace, M.D., professor of anesthesiology, University of California San Diego School of Medicine.

Results showed there was a dose-dependent reduction in pain intensity from inhaled cannabis, which the authors noted is consistent with results of other trials of the drug for diverse neuropathic pain syndromes.

"The dose dependent analgesic effect was evident for both spontaneous and evoked pain in the trial subjects, but it was more consistent on spontaneous pain," said Wallace.

The also authors reported that all subjects experienced either euphoria or somnolence, which may limit the acceptability of cannabis as an analgesic. However, in measuring the impact of inhaled cannabis impact on cognition (attention and memory), they found modest effects with no dramatic declines or impairments.

"These findings along with previous studies suggest that cannabis might have analgesic benefit in neuropathic pain syndromes, including treatment-refractory DPN," said Wallace.