Are oral cannabinoids safe and effective in refractory neuropathic pain?

Although cannabinoids have anti-hyperalgesic effects in animal models of nerve injury, there are currently very few prospective trials of the efficacy of cannabinoids in neuropathic pain in humans. This open label prospective study investigated the safety, tolerability and analgesic benefit of oral Delta-9-tetrahydrocannabinol (THC) titrated to a maximal dosage of 25 mg/day in 8 consecutive patients with chronic refractory neuropathic pain. Spontaneous ongoing and paroxysmal pain, allodynia and paresthesias were assessed. The sensory and affective components of pain using the McGill pain questionnaire, quality of life, mood, anxiety and functionality were also evaluated. Seven patients suffered from side effects necessitating premature arrest of the drug in 5 of them. THC (mean dosage: 16.6+/-6.5 mg/day) did not induce any significant effects on ongoing and paroxysmal pain, allodynia, quality of life, anxiety/depression scores and functional impact of pain. These results do not support an overall benefit of THC in pain and quality of life in patients with refractory neuropathic pain.