What’s more, marijuana remains classified as a Schedule I agent.19 Because of its high potential for abuse, physicians in states where medical marijuana has been legalized should adhere to off-label prescribing principles: Recommend it only after standard medications, including FDA-approved cannabinoids, and nonpharmaceutical approaches have proven to be inadequate.6,20,21
Medical marijuana for your patient? A look at the evidence
The meta-analysis cited earlier included 79 randomized clinical trials (RCTs) of medical marijuana used for a variety of conditions in a number of delivery modes. However, only 4 were judged to be of low risk of bias.5 Nonetheless, here’s a look at this and other evidence.
Chronic and neuropathic pain
Twenty-eight of the 79 studies addressed chronic pain, with half assessing the oromucosal spray (nabiximols). Most others studied marijuana that was smoked or inhaled. Neuropathic pain was most frequently studied, but cancer pain, fibromyalgia, and musculoskeletal pain, among others, were also evaluated.5
The average number of patients who reported a reduction in pain of ≥30% was greater with marijuana compared with placebo (odds ratio=1.41; 95% confidence interval, .99-2.0). Delivery mode did not affect outcomes; different forms of administration were not associated with any significant difference in pain relief. Nor were there significant differences in results among the various pain conditions studied. Notably, however, quality of life measurements did not reflect any overall improvement.5
The authors of a literature review of marijuana for chronic and neuropathic pain and MS-induced spasticity did find high-quality evidence of its efficacy in several of the trials they assessed.6 And a review of well-conducted observational trials of smoked marijuana as a treatment for severe neuropathic pain revealed that it may be indicated for those who fail to respond to FDA-approved cannabinoids and standard analgesics.10 Neither functional status nor quality of life was evaluated, however, and none of the observational studies compared smoked cannabis to standard analgesics.
Notably, the authors did not recommend smoked marijuana for pain conditions such as low back pain and fibromyalgia, which are commonly seen in practice. That’s because the safety and efficacy of smoked cannabis has not been studied for these conditions and because evidence-based treatments for these disorders exist.10
CASE › Before considering medical marijuana for Ms. B, you suggest a trial of dronabinol. The patient agrees, and you prescribe 2.5 mg twice a day. You schedule a visit in 4 weeks to review the drug’s efficacy and tell her to call if she develops psychiatric symptoms, such as hallucinations or paranoia, or impaired cognition. You also advise her that dronabinol may increase the risk of auto accidents and caution her to avoid driving for 6 hours after taking the drug—or longer if she experiences an initial “high.”
MS symptoms
A comprehensive review of medical marijuana studies spanning nearly 7 decades revealed 12 trials focusing on MS—and found its use in treating MS-related spasticity supported by high-quality evidence.6
Two of the largest studies were done in the UK.7,8 One multicenter trial included 630 participants randomized to treatment with an oral cannabinoid extract, THC, or placebo for 6 weeks.7
There was no change in the primary outcome measure, the Ashworth spasticity scale. However, there was a treatment effect on patient-reported spasticity and pain, with improvement in spasticity reported by 61% of those treated with the cannabinoid extract, 60% of those treated with THC, and 46% of those treated with placebo.7
The other UK trial involved 22 centers and 279 patients, randomized to either oral cannabis extract or placebo. The primary outcome measure involved a category rating scale that reported on change in muscle stiffness since baseline and on body pain, spasms, and sleep quality. This study used a 2-week titration phase and a 10-week maintenance phase. The rate of relief from muscle stiffness after 12 weeks was almost twice as high in the cannabis extract group (29%) compared with placebo (16%).8
A systematic review of the efficacy and safety of medical marijuana by the American Academy of Neurology (AAN) concluded that oral cannabis extract, THC, and nabiximols are “probably effective” in reducing patient-centered measures of spasticity and pain associated with MS.9
Little help for other neurologic disorders. Studies of the efficacy and safety of medical marijuana for other neurologic disorders have been less encouraging. The AAN concluded that cannabinoids are probably ineffective for the treatment of tremors, and that oral cannabis extract is probably ineffective for treating levodopa-induced dyskinesias in patients with Parkinson’s disease.