“Spasticity is a common and disabling symptom that remains a substantial problem for many patients with multiple sclerosis. Some patients have adverse effects from conventional antispasticity medications; for others, spasticity persists despite treatment. A report from the Institute of Medicine in the United States concluded that the active compounds of cannabis (marijuana) are potentially effective in treating neurologic conditions and “should be tested rigorously in clinical trials.” There is evidence that the cannabinoid receptors CB₁ and CB₂ may be involved in the control of spasticity in multiple sclerosis² and that the endogenous ligand of CB₁, anandamide, is itself an effective antispasticity agent.³ CB₁ receptors are primarily presynaptic; their activation inhibits calcium influx and glutamate release, and reduces neuronal excitability by activating somatic and dendritic potassium channels.^“

“Although many patients with multiple sclerosis endorse smoking cannabis as therapy, evidence that it relieves spasticity is largely anecdotal, as most trials focus on orally administered cannabinoids. We sought to assess the safety and efficacy of smoked cannabis versus placebo in patients with multiple sclerosis who have treatment-resistant spasticity.”