IRCT2014031717045N1 IRCT 2014-10-04 Guilan University of Medical Sciences Comparing the clinical response of obsessive-compulsive patients refractory to serotonin reuptake inhibitor regimen with and without lamotrigine; a double-blind placebo controlled study Comparing the clinical response of obsessive-compulsive patients refractory to serotonin reuptake inhibitor regimen with and without lamotrigine; a double-blind placebo controlled study 2014-04-21 anticipated 60 Complete https://irct.ir/trial/15779 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment. 2-3 Obsessive-compulsive patients. Intervention 1: Patients in intervention group continue the previous medication, Serotonin Reuptake Inhibitors, all over the study. Intervention group receive capsules containing lamotrigine, starting at 25 mg daily, titrated up to 25 mg weekly to reach the target level of 100 mg at the end of the 4th week. At this point, the dosage will be maintained at the same level until the end of the study, which lasts 90 days. Intervention 2: Patients in the placebo group continue previous medication, Serotonin Reuptake Inhibitors, all over the study. Patients in the placebo group receive one capsule daily. The number, shape and size of the capsules in the placebo group are exactly the same as those in the intervention group.