Cannabidiol After Multi-Trauma for Pain and Opioid Therapy

The level of pain in the acute phase after injury is a predictor of the development of chronic pain. Chronic pain is defined as pain that persists for more than 3 months post-accident and impairs functional recovery. Mechanistically, it has been shown that acute nonspecific inflammation triggered after peripheral injury results in the continuous release of proinflammatory cytokines that weaken the blood-brain barrier, facilitating the entry of toxins that can invade the central nervous system (CNS). The resulting sustained inflammation of the CNS plays an important role in establishing the maladaptive plasticity process underlying pain chronification. Cannabidiol (CBD), a component of cannabis devoid of addictive or psychotropic effects, stands out as a potential therapeutic agent given its analgesic and anti-inflammatory properties as well as its potential to enhance the biomechanical properties of bone healing. Given the excellent safety profile of CBD and its inhibitory effects on microglial activity, the primary mechanism of neuroinflammation and pain, CBD has the potential to promote acute pain relief while reducing reliance on addictive opioid treatments, hence facilitating recovery in trauma patients.

This study is a randomized, placebo controlled, human pilot clinical trial evaluating the effects of two doses (low and moderate) of CBD vs. placebo on pain after orthopaedic trauma.

Risks of adverse effects are considered low given the demonstrated excellent safety profile of CBD. CBD was also shown to accentuate opioid analgesic effects, thus reducing required opioid doses for patient comfort. The most likely adverse events associated with CBD in adult patients include somnolence, fatigue, drowsiness and decreased appetite. Access to on-duty emergency physicians at the recruiting site will be provided during the entire treatment duration.

A 30% relative pain intensity reduction on the VAS (expected response of 50% or more in the CBD group and expected 20% in the placebo group) has been used extensively to reflect clinically significant pain relief in clinical trials. Based on a Fisher's exact test, a sample size of 225 participants (3 groups of 75) will be required to reach a power of 80% to detect a statistically significant difference in the proportion of patients who reaches 30% pain reduction between the CBD groups and placebo at 1-month post-injury, assuming a dropout rate of 20% and a significance level of 5%. These parameters are taken from a successful randomised, placebo-controlled clinical trial using Sativex© in treating 125 neuropathic pain patients. Moreover, considering that the placebo group may ingest more opiates and that the anticipated inter-group effect at one month may be reduced to 20%, a total sample size of 225 subjects could be required to achieve 80% power, assuming a drop-out rate of 20% and a significance level of 5%.

Our group has ensured the feasibility of conducting such a pilot clinical trial in multi-trauma patients with the recruitment of 110 patients in less than 18 months to take part in a 10-session, outpatient treatment trial. A partnership with Canadian company EmpowerPharm will enable the use of pharmaceutical-grade synthetic CBD samples and identical placebos. The pharmacokinetic profile of the CBD product has been established.

• Response Rate - 50 Percent or Greater Reduction in Pain Intensity on a Visual Analog Scale (VAS) [Time frame: 4 weeks]
• Change in Pain Rating on the Brief Pain Inventory Short Form (BPI-sf) Between Interventions [Time frame: 4 weeks and 3 months]
• Change in Blood Level Inflammation Over Time and Between Interventions [Time frame: Baseline, 4 weeks and 3 months]
• Opioid Usage Monitoring [Time frame: Ongoing from baseline to 3 months]
• Change in the Orthopaedic Function Using The Short Musculoskeletal Function Assessment (SMFA) Questionnaire Between Interventions [Time frame: 4 weeks and 3 months]
• Change in Quality of Life Using the Short Form (36) Health Survey Between Interventions [Time frame: 4 weeks and 3 months]
• Change in Sleep Quality Using the Pittsburgh Sleep Quality Index (PSQI) Between Interventions [Time frame: 4 weeks and 3 months]
• Change in Depression Symptoms Assessment Using the Beck's Depression Inventory-II Between Interventions [Time frame: Baseline, 4 weeks and 3 months]
• Change in Anxiety Symptoms Assessment Using the Beck's Anxiety Inventory Between Interventions [Time frame: Baseline, 4 weeks and 3 months]
• Change in Speed of Information Processing using Symbol Search from the WAIS-IV Battery Between Intervention [Time frame: Baseline, 4 weeks and 3 months]
• Change in Attention using Elevator counting with distraction from the Test of Everyday Attention Battery Between Intervention [Time frame: Baseline, 4 weeks and 3 months]
• Change in Attention using Elevator counting from the Test of Everyday Attention Battery Between Intervention [Time frame: Baseline, 4 weeks and 3 months]