Does the cannabinoid dronabinol reduce central pain in multiple sclerosis? Randomised double blind placebo controlled crossover trial

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Abstract
Objective To evaluate the effect of the oral synthetic δ-9-tetrahydrocannabinol dronabinol on central neuropathic pain in patients with multiple sclerosis. Design Randomised double blind placebo controlled crossovertrial. Setting Outpatient clinic, University Hospital of Aarhus, Denmark. Participants 24 patients aged between 23 and 55 years with multiple sclerosis and central pain. Intervention Orally administered dronabinol at a maximum doseof 10 mg daily or corresponding placebo for three weeks (15-21days), separated by a three week washout period. Main outcome measure Median spontaneous pain intensity (numericalrating scale) in the last week of treatment. Results Median spontaneous pain intensity was significantlylower during dronabinol treatment than during placebo treatment(4.0 (25th to 75th centiles 2.3 to 6.0) v 5.0 (4.0 to 6.4),P = 0.02), and median pain relief score (numerical rating scale)was higher (3.0 (0 to 6.7) v> 0 (0 to 2.3), P = 0.035). Thenumber needed to treat for 50% pain relief was 3.5 (95% confidenceinterval 1.9 to 24.8). On the SF-36 quality of life scale, thetwo items bodily pain and mental health indicated benefits fromactive treatment compared with placebo. The number of patientswith adverse events was higher during active treatment, especiallyin the first week of treatment. The functional ability of themultiple sclerosis patients did not change. Conclusions Dronabinol has a modest but clinically relevantanalgesic effect on central pain in patients with multiple sclerosis.Adverse events, including dizziness, were more frequent withdronabinol than with placebo during the first week of treatment.