Effect of smoked cannabis on painful diabetic peripheral neuropathy

There is emerging evidence that the cannabinoids are effective in neuropathic pain. A randomized, double-blinded, placebo controlled crossover design methodology was conducted in sixteen patients with painful diabetic peripheral neuropathy (7 women, 9 men). Subjects participated in four sessions where they were exposed to placebo, low (1% tetrahydrocannabinol, THC), medium (4% THC), or high (7% THC) dose of cannabis. Baseline spontaneous pain, evoked pain and cognitive testing were performed. Subjects were then administered aerosolized cannabis or placebo and the pain intensity and subjective highness score was measured at 5, 15, 30, 45, 60 minutes and then every 30 minutes for an additional 3 hours. Cognitive testing was performed at 5 and 30 minutes and then every 30 minutes for an additional 3 hours. Area under the spontaneous pain versus time curve was the primary endpoint. Overall effect of cannabis dose on spontaneous pain was significant (p=0.029) with only the high dose reaching significance (p=0.013). There was an overall difference in mean lowest achieved spontaneous pain score between groups (0.044) with the high dose achieving the lowest mean pain score (p=0.017). There was a trend for significant effects of the cannabis on evoked pain. Overall effects for brush (p=0.085) and pin prick (p=0.199) pain trended toward significance with the high dose most effective (brush p=0.057, pin prick p=0.144). There was a dose dependent increase in the subjective highness score reported after cannabis exposure which persisted into the late time course. There was a significant difference in two of the three neuropsychological tests (Paced Auditory Serial Addition Test, p=0.005; Trail Making Test B, p=0.049; Trail Making Test A, p=0.362). These results are consistent with evidence in other neuropathic pain syndromes and suggest additional research is warranted.