Efficacy of Inhaled Cannabis in Diabetic Peripheral Neuropathy

INVESTIGATOR: Mark Wallace, M.D.

STUDY LOCATION: University of California, San Diego

PROJECT TITLE: Efficacy of Inhaled Cannabis in Diabetic Peripheral Neuropathy

PROJECT TYPE: Clinical Study

STATUS: COMPLETED

RESULTS:

A randomized, double-blinded, placebo controlled crossover study was conducted in 16 patients with painful diabetic peripheral neuropathy to assess the short-term efficacy and tolerability of inhaled cannabis. In a crossover design, each participant was exposed to 4 single dosing sessions of placebo or to low (1% tetrahydrocannabinol [THC]), medium (4% THC), or high (7% THC) doses 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, and 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. The primary analysis compared differences in spontaneous pain over time between doses using linear mixed effects models. There was a significant difference in spontaneous pain scores between doses (P < .001). Specific significant comparisons were placebo versus low, medium, and high doses (P = .031, .04, and <.001, respectively) and high versus low and medium doses (both P < .001). There was a significant effect of the high dose on foam brush and von Frey evoked pain (both P < .001). There was a significant negative effect (impaired performance) of the high dose on 2 of the 3 neuropsychological tests (Paced Auditory Serial Addition Test, Trail Making Test Part B.

The full results of this study have been published in the Journal of Pain.

ABSTRACT:

Neuropathic pain is caused by an insult to the nervous system and accounts for 25-50% of all pain clinic visits. Excluding low back pain, diabetic peripheral neuropathy is the most common neuropathic pain syndrome with an estimated prevalence of 600,000 cases in the United States. There are only 5 medications approved by the FDA for the treatment of neuropathic pain with only 2 out of the 5 approved for the treatment of diabetic peripheral neuropathy. Currently, there is a desperate need for more therapeutic agents for the treatment of neuropathic pain. We propose to use painful diabetic peripheral neuropathy (DPN) patients to study the efficacy of inhaled cannabis on neuropathic pain. We will enroll 20 subjects with each subject acting as their own control; receiving both placebo and three doses of inhaled aerosolized cannabis (low, medium, and high) in random order each separated by at least two weeks. Subjects will be assessed for reduction in pain, changes in normal sensation, changes in cognition, and effects of cannabis on experimentally induced pain. Our hypothesis is as follows:

1. Cannabis will result in a dose dependent decrease in the spontaneous pain and qualitative pain descriptors.
2. Cannabis will have no effect on acute sensory thresholds as measured by the QST.
3. Pain relief will occur at cannabis doses that do not significantly affect cognitive function.

Cannabis will decrease experimental pain as measured by the BTS. The effect on the BTS will correlate with the decrease in spontaneous pain of DPN.