An enriched-enrolment, randomized withdrawal, flexible-dose, double-blind, placebo-controlled, parallel assignment efficacy study of nabilone as adjuvant in the treatment of diabetic peripheral neuropathic pain

Cannabinoids are emerging as potential options for neuropathic pain treatment. This study evaluated an oral cannabinoid, nabilone, in the treatment of refractory human diabetic peripheral neuropathic pain (DPN). We performed a single-center, randomized, double-blind, placebo-controlled, flexible-dose study with an enriched enrolment randomized withdrawal design. DPN subjects with a pain score >= 4 (0-10 scale) continued regular pain medications and were administered single-blinded adjuvant nabilone for 4 weeks. Subjects achieving >= 30% pain relief (26/37) were then randomized and treated with either flexible-dose nabilone 1-4 mg/day (n = 13) or placebo (n = 13) in a further 5-week double-blind treatment period, with 30% (11/37) of subjects deemed run-in-phase nabilone nonresponders. For nabilone run-in-phase responders, there was an improvement in the change in mean end-point neuropathic pain vs placebo (mean treatment reduction of 1.27; 95% confidence interval 2.29-0.25, P = 0.02), with an average nabilone dose at end point of 2.9 +/- 1.1 mg/day, and improvements from baseline for the anxiety subscale of the Hospital Anxiety and Depression Scale, the Medical Outcomes Study sleep scale problems index, and the European Quality of Life-5-Domains index score (each P < 0.05). Nabilone run-in-phase responders reported greater global end-point improvement with nabilone than with placebo (100% vs 31%; P < 0.05). Medication-related confusion led to discontinuation in 2/37 subjects during single-blind nabilone treatment. Potential unmasking occurred in 62% of both groups. Flexible-dose nabilone 1-4 mg/day was effective in relieving DPN symptoms, improving disturbed sleep, quality of life, and overall patient status. Nabilone was well tolerated and successful as adjuvant in patients with DPN. (C) 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.