Effect of dronabinol on central neuropathic pain after spinal cord injury: a pilot study

To test the efficacy and safety of a cannabinoid, dronabinol, compared with an active control, diphenhydramine, in relieving neuropathic pain in persons with spinal cord injury. A randomized, controlled, double-blind, crossover pilot study. Seven adults with spinal cord injury and neuropathic pain below the level of injury participated. Two participants withdrew while receiving dronabinol, their first medication. For the remaining five participants, change in pain on a scale of 0-10 from baseline to the end of the maintenance phase did not differ significantly between the two medications (mean change, dronabinol: 0.20 ± 0.837, range = -1.00 to 1.00; diphenhydramine: -1.80 ± 2.490, range = -6.00 to 0; Wilcoxon Z = 1.63, P = 0.102). Similar results were found when the average of the two ratings during the maintenance phase was used (dronabinol: -0.20 ± 0.671, range = -0.50 to 1.00; diphenhydramine: -1.40 ± 1.245, range = -3.50 to -0.50; Wilcoxon Z = 1.60, P = 0.109). The most common side effects were dry mouth, constipation, fatigue, and drowsiness for both medications. On average, dronabinol was no more effective than diphenhydramine for relieving chronic neuropathic pain below the level of injury.