Cannabinoids and Pain
Wade et al. (2003) note that delta-9-tetra hydrocannabinol (THC) and other cannabinoids have been shown to improve both tremor and spasticity in animal models of multiple sclerosis supported by anecdotal reports that cannabis relieves some of the troublesome symptoms of multiple sclerosis and spinal cord injury (Baker et al. 2000; Consroe et al. 1997; Dunn & Davis 1974; Martyn et al. 1995; Meinck et al. 1989; Petro & Ellenberger 1981; Ungerleider et al.1987). There is a clinical impression that marijuana smoking is very common among patients post-SCI; however, there are social and legal implication to its use and medical concerns about smoking as a delivery system. For a more complete discussion, refer to the Cannabinoids chapter pain page on SCIRE.
Discussion
Wilsey et al. (2016) found cannabis vapor significantly reduced pain post SCI compared to placebo vapor. Rintala et al. (2010) examined the effect of dronabinol versus an active control (diphenhydramine) on pain post SCI. The study found no significant difference on pain intensity between the two treatments.
Hagenbach et al. (2007) conducted a study examining primarily the effectiveness of THC in improving spasticity and secondarily, in improving pain with SCI individuals. In the first phase of the study, 22 individuals received 10mg of oral THC which was then dose titrated until maximum tolerance or treatment dose was reached for 6 weeks. The study found a significant reduction in the pain of SCI individuals post treatment (p=0.047). The third phase of the study involved a double blind randomized control trial which included 13 of the previously mentioned individuals receiving either individual maximum treatment dosage previously determined or a placebo dose. In this phase, Hagenbach et al. (2007) found individuals in the treatment group had no significant pain reduction compared to those in the placebo group.
Given that marijuana has anecdotally been thought to have benefits for post-SCI pain, Wade et al. (2003) conducted an RCT of sublingual 2.5 mg THC and/or cannabidiol and found that it helped to reduce pain, muscle spasm, spasticity and sleep in a group of largely multiple sclerosis patients with neuropathic pain. It is of note that only a small percentage of the patients in this study had spinal cord injuries hence did not meet inclusion criteria. Cannabinoids are a promising treatment, which would benefit from other studies.
Conclusion
There is level 1b evidence (Wilsey et al. 2016) that cannabis vapour improves pain post SCI.
There is conflicting level 2 evidence (from one RCT: Hagenbach et al. 2007) for the use of delta-9-tetra hydrocannabinol in reducing spastic pain in SCI individuals.
There is level 2 evidence (from one RCT: Rintala et al. 2010) that dronabinol is not effective in reducing pain intensity post SCI.
