Efficacy Study of Dextromethorphan to Treat Rheumatoid Arthritis

Biologic-naïve rheumatoid arthritis (RA) patients who fulfilled the 2010 criteria of the American College of Rheumatology (ACR) for RA were enrolled. All patient were randomized to a 6-month treatment with either oral DXM [dextromethorphan hydrobromide; Detosiv Slow Release® (60mg per tablet, Lotus Pharmaceutical Company, Taipei, Taiwan) with T1/2 = 7.75h, Tmax = 4.83h, Cmax = 14.6 ng mL-1 and mean residual time = 5.86 h, 120mg per day with once daily dose taken after breakfast] or placebo pills with the same appearance as DXM tablets. The randomization was performed by the pharmacy of the Taichung Veterans General Hospital. Non-study medications were not changed during the course of study.

Twenty-four patients received add-one DXM therapy and the other 24 patients received traditional DMARDs alone in stable dose. Disease activity was assessed by the 28-joint disease activity score (DAS28) before starting add-on DXM therapy (as a baseline) and at the end of 6 months of therapy with or without add-on DXM. Patients were categorized as good, moderate or poor responders based on the amount of change in the DAS28 and the level of DAS28 reached. Good responders were defined as patients who had a decrease in DAS28 from baseline (∆DAS28)>1.2 and a DAS28≦3.2 at evaluation time; moderate responders had either ∆DAS28>1.2 and a DAS28>3.2 or ∆DAS28 of 0.6-1.2 and a DAS28≦5.1 at evaluation time; and poor responders were those who had either ∆DAS28\<0.6 or a DAS28>5.1 at evaluation time.