Inhaled cannabis had a significant effect on neuropathic pain that appears to be dose-dependent, in the first published research on cannabinoids for painful diabetic neuropathy in humans.

In a study appearing in The Journal of Pain, researchers from the University of California, San Diego conducted a randomized, double-blind, placebo-controlled crossover study of 16 patients with painful diabetic neuropathy to evaluate the short-term efficacy and tolerability of inhaled cannabis. Each participant was exposed to four single dosing sessions of low (1% tetrahydrocannabinol [THC]), medium (4% THC), or high (7% THC) doses of cannabis, or placebo. Baseline spontaneous and evoked pain were measured, and cognitive testing was performed; the participants then received aerosolized cannabis or placebo and the pain intensity and subjective “highness” score was measured at 5, 15, 30, 45, and 60 minutes and then every 30 minutes for an additional three hours. Cognitive testing was performed at 5 and 30 minutes and then every 30 minutes for an additional three hours.

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A dose-dependent reduction was seen in diabetic peripheral neuropathy pain in patients with treatment-refractory pain, with significant differences in spontaneous pain scores between doses, a significant effect of the high dose on foam brush and von Frey evoked pain, and a significant negative effect (impaired performance) on two of the three neuropsychological tests. However, in measuring the impact of inhaled cannabis impact on cognition, the researchers found modest effects with no dramatic declines or impairments.

Despite all subjects experiencing euphoria or somnolence, which may limit the acceptability of cannabis as an analgesic, the authors conclude that cannabis could still provide benefits in neuropathic pain syndromes that include treatment-refractory diabetic neuropathy.

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