ObjectivesThe therapeutic limitations of mainstay psychopharmacological treatments of obsessive-compulsive disorder (OCD) warrant the clinical testing of further add-on agents in order to improve patients’ clinical outcomes. The novel antiepileptic drug pregabalin (PGB) could be such an adjunctive agent in view of its attested efficacy in other anxiety disorders, especially generalized anxiety disorder.MethodsWe report on an open-label add-on trial of the novel antiepileptic pregabalin (PGB) in 10 (4 male and 6 female) OCD-patients resistant or only partial responders to an - at least 6-month long - combination of serotonin reuptake inhibitors with atypical antipsychotic.Patients’ regimens were stable for at least the last six months before their enrolment in the study and were maintained unchanged throughout the trial. Patients’ assessment took place weekly during the trial. PGB's dosage titration was conditional upon both degree of clinical response and side-effects during past week. Patients’ pre- and post- PGB ratings on the Y-BOCS were compared by means of paired samples t-test.ResultsAdjunctive PGB at 225–675 mg/d was well-tolerated and led within 4–12 weeks to patients’ substantial improvement in their OCD symptoms, as reflected in their scores on the Y-BOCS (t = 9.83, p < 0.001). Equally robust was Cohen's d measure of effect-size (d = 2,99).ConclusionsDespite the several limitations of the study, its results suggest that adjunctive PGB might be a safe and efficacious new agent in the treatment of drug-resistant OCD.