An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia.

In this experimental randomized placebo-controlled 4-way crossover trial, we explored the analgesic effects of inhaled pharmaceutical-grade cannabis in twenty chronic pain patients with fibromyalgia. We tested four different cannabis varieties with exact knowledge on their [INCREMENT]-tetrahydrocannabinol (THC), and cannabidiol (CBD) content: Bedrocan® (22.4 mg THC, < 1 mg CBD), Bediol® (13.4 mg THC, 17.8 mg CBD), Bedrolite® (18.4 mg CBD, < 1 mg THC) and a placebo variety without any THC or CBD. Following a single vapor inhalation, THC and CBD plasma concentrations, pressure and electrical pain thresholds, spontaneous pain scores and drug high were measured for 3 hours. None of the treatments had an effect greater than placebo on spontaneous or electrical pain responses, although more subjects receiving Bediol® displayed a 30% decrease in pain scores compared to placebo (90% vs. 55% of patients, p = 0.01), with spontaneous pain scores correlating with the magnitude of drug high (ρ = -0.5, p < 0.001). Cannabis varieties containing THC caused a significant increase in pressure pain threshold relative to placebo (p < 0.01). CBD inhalation increased THC plasma concentrations but diminished THC-induced analgesic effects, indicative of a synergistic pharmacokinetic but antagonistic pharmacodynamic interactions of THC and CBD. This experimental trial shows the complex behavior of inhaled cannabinoids in chronic pain patients with just small analgesic responses after a single inhalation. Further studies are needed to determine long-term treatment effects on spontaneous pain scores, THC-CBD interactions and the role of psychotropic symptoms on pain relief.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND) , where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.