Tehran University of Medical Sciences Iranian Journal of Psychiatry 1735-4587 11 2 2016 06 01 104 114 EN Mohammadrasoul Khalkhali Department of Psychiatry, Guilan University of Medical Sciences, Rasht, Iran Setareh Aram‎ Department of Psychiatry, Guilan University of Medical Sciences, Rasht, Iran Homa Zarrabi Department of Psychiatry, Guilan University of Medical Sciences, Rasht, Iran Moosa Kafie Department of Psychology, Guilan University, Rasht, Iran Abtin Heidarzadeh Department of Community Medicine, Guilan University of Medical Sciences , Rasht, Iran 2016 05 31 2016 05 31 Objective: Serotonin reuptake inhibitors are frequently used in first-line treatments for patients ‎with obsessive-compulsive disorder. Nevertheless, many of these patients do not ‎respond well to initial therapy. The hypothesis of glutamatergic dysfunction in specific ‎brain regions has been proposed in the pathophysiology of obsessive-compulsive ‎disorder. This study was designed to evaluate the possible efficacy of lamotrigine, a ‎glutamatergic agent in Serotonin reuptake inhibitors-resistant patients with obsessive-‎compulsive disorder.‎ Method: This study was a 12-week, double blind, randomized, placebo-controlled trial of ‎adjunctive fixed-doses of lamotrigine (100 mg) to Serotonin reuptake inhibitors therapy ‎in obsessive-compulsive disorder. Eligible subjects who had a total Y-BOCS of 21 or ‎above were randomly assigned to receive adjunctive treatment with either lamotrigine ‎‎(n = 26), or placebo (n = 27). Response to lamotrigine was defined as clinical ‎improvement (>25% decrease in the total Y-BOCS score), which was administered at ‎weeks 0, 8 and 12.‎ Results: At the endpoint (week 12), significant differences were observed in obsession, ‎compulsion, and total Y-BOCS scores comparing lamotrigine to placebo (P = 0.01, ‎‎0.005 and 0.007 respectively). The mean reduction in obsession, compulsion and total ‎scores in lamotrigine group was about 4.15, 4.50 and 8.73, respectively. Similarly, the ‎mean reductions in the placebo group were 2.52, 2.56 and 5.07. Effect sizes for efficacy ‎measures were calculated by Cohen’s d, and it was calculated as 0.54 for the total ‎YBOCS.‎ Conclusion: Our findings provide evidence that this augmentation is well tolerated and may be an ‎effective strategy for patients with refractory obsessive-compulsive disorder.‎‎ https://ijps.tums.ac.ir/index.php/ijps/article/view/709 https://ijps.tums.ac.ir/index.php/ijps/article/download/709/558