Abstract

Aim: The role of the glutamatergic system in the pathogenesis of obsessive–compulsive disorder (OCD) has been shown by numerous studies. The aim of the present randomized, double-blind, placebo-controlled, 12-week trial was to assess the efficacy and tolerability of amantadine as an adjuvant to fluvoxamine in the treatment of patients with moderate to severe OCD. Methods: One hundred patients diagnosed with moderate to severe OCD were randomized into two parallel groups to receive fluvoxamine (100 mg twice a day) plus placebo or fluvoxamine (100 mg twice a day) plus amantadine (100 mg daily) for 12 weeks. All patients received 100 mg/day fluvoxamine for 28 days followed by 200 mg/day for the rest of the trial, regardless of their treatment groups. Patients were evaluated for response to treatment using the Yale–Brown Obsessive Compulsive Scale (Y-BOCS) at baseline and at Weeks 4, 10, and 12. The main outcome measure was to assess the efficacy of amantadine in improving the OCD symptoms. Results: Repeated-measure analysis of variance showed a significant effect for Time × Treatment interaction (Greenhouse–Geisser corrected: F = 3.84, d.f. = 1.50, P = 0.03) in the Y-BOCS total score and a significant effect for Time × Treatment interaction (Greenhouse–Geisser corrected: F = 5.67, d.f. = 1.48, P < 0.01) in the Y-BOCS Obsession subscale score between the two groups. Conclusion: The results of this study suggest that amantadine may be effective as an augmentative agent in the treatment of moderate-to-severe OCD. © 2018 The Authors. Psychiatry and Clinical Neurosciences © 2018 Japanese Society of Psychiatry and Neurology