Nabilone as an Adjunctive to Gabapentin for Multiple Sclerosis-Induced Neuropathic Pain: A Randomized Controlled Trial

Background: Neuropathic pain (NPP) is a chronic syndrome suffered by patients with multiple sclerosis (MS), for which there is no cure. Underlying cellular mechanisms involved in its pathogenesis are multifaceted, presenting significant challenges in its management. Methods: A randomized, double-blind, placebo-controlled study involving 15 relapsing-remitting MS patients with MS-induced NPP was conducted to evaluate nabilone combined with gabapentin (GBP). Eligible patients stabilized on GBP (>/=1,800 mg/day) with inadequate pain relief were recruited. Nabilone or placebo was titrated over 4 weeks (0.5 mg/week increase) followed by 5-week maintenance of 1 mg oral nabilone (placebo) twice daily. Primary outcomes included two daily patient-reported measures using a 100-mm visual analog scale (VAS), pain intensity (VASpain), and impact of pain on daily activities (VASimpact). Hierarchical regression modeling was conducted on each outcome to determine if within-person pain trajectory differed across study groups, during 63-day follow-up. Results: After adjustment for key patient-level covariates (e.g., age, sex, Expanded Disability Status Scale, duration of MS, baseline pain), a significant group x time(2) interaction term was reported for both the VASpain (P < 0.01) and VASimpact score (P < 0.01), demonstrating the adjusted rate of decrease for both outcomes was statistically greater in nabilone vs placebo study group. No significant difference in attrition rates was noted between treatments. Nabilone was well tolerated, with dizziness/drowsiness most frequently reported. Conclusion: Nabilone as an adjunctive to GBP is an effective, well-tolerated combination for MS-induced NPP. The results of this study identify a novel therapeutic combination for use in this population of patients predisposed to tolerability issues that may otherwise prevent effective pain management.