or medical cannabis, these types of trials are limited and hampered by existing federal and state regulations and, often, a lack of consistency in the composition of the medical cannabis available to patients.
Despite the scarcity of clinical trial data, there are a multitude of reports from patients who use medical cannabis and find relief for a wide variety of conditions. These include intractable seizure disorders, inflammatory diseases, chronic pain, spasticity associated with muscular dystrophy, mood disorders, post-traumatic stress disorder, and others. Basic scientific research, which looks at the biology of cannabinoids and their receptors, provides data that supports the therapeutic potential of medical cannabis, and offers insights into the potential mechanisms for the benefits anecdotally reported by patients.1
Fortunately, the past decade has brought an increase in the number, scope and rigor of clinical trials in medical cannabis. These trials have employed cannabis, cannabis-based extracts, and synthetic cannabinoids delivered by smoking, vaporization, oral, and sublingual or mucosal routes. Representative studies include a series of randomized clinical trials conducted by the University of California Center for Cannabis Research (CMCR), which investigated the short-term efficacy of smoked cannabis for neuropathic pain. Participants were randomized to smoke cannabis cigarettes containing 1-8% THC by weight or placebo cigarettes from which THC had been extracted. Two trials enrolled patients with painful HIV peripheral neuropathy; one consisted of mixed neuropathic pain (complex regional pain syndrome, peripheral neuropathy, and traumatic focal nerve or spinal cord injury). Results consistently indicated that cannabis significantly reduced pain intensity, from a 34-40% decrease on cannabis compared to a 17-20% decrease on placebo. Significantly more reported at least a 30% reduction in pain on cannabis compared to placebo, a threshold, which is generally associated with reports of improved quality of life.2
Concerns regarding the hazards of smoking and limitations associated with the oral delivery of cannabis have led researchers to explore alternate delivery routes for medical cannabis. Sublingual delivery of whole cannabis plant extract, which employ metered spray devices to deliver measured doses of THC are licensed outside of the US for cancer pain and neuropathic pain and spasticity associated with multiple sclerosis (MS); trials are ongoing in the US (nabiximols, Sativex®). A recent meta-analysis looking at nabiximols in over 600 patients with spasticity associated with MS showed that the mean intensity of patient rated spasticity was significantly reduced compared to placebo; the proportion of those with a 30% reduction (responders) was also significantly greater (37% on nabiximols vs. 26% on placebo).2 This improvement appeared to be maintained over 1 year of follow-up. The CMCR also conducted a study comparing smoked cannabis vs. placebo cannabis in those with MS-associated spasticity and found a significant reduction among those receiving active cannabis.3