333. COMPARISON OF THE EFFICACY AND TOLERABILITY BETWEEN PAROXETINE AND ESCITALOPRAM IN PATIENTS WITH OBSESSIVE-COMPULSIVE DISORDER IN REAL-WORLD CLINICAL SETTINGS IN JAPAN

Abstract Background Obsessive-Compulsive Disorder (OCD) is a chronic psychiatric disorder characterized by obsessions and compulsions. Selective serotonin reuptake inhibitor (SSRI) is the first-line treatment with proven efficacy in controlled settings, which often necessitates higher SSRI doses than depression. In Japan, paroxetine (PXT), titrated up to 50 mg, offers dose flexibility but requires over five weeks for gradual titration in outpatient care. Escitalopram (ESP), limited to 20 mg, has a simpler schedule, allowing faster evaluation of efficacy and tolerability, despite its lower maximum dose. Although ESP is only approved for depression in Japan, it is widely used off-label for OCD, especially for childhood OCD. Aims & Objectives This study sought to prospectively examine the comparative efficacy and tolerability comparing between paroxetine and escitalopram in routine outpatient settings. Method This study enrolled forty-two outpatients of our hospital who met DSM-5 criteria for OCD and gave us written informed consent to participate in this study. Twenty-two patients were randomly assigned to the PXT group, and twenty initially received ESP. PXT was initiated at 10 mg/day and titrated to a maximum of 50 mg/day with an interval of at least one week between dose increases, while ESP was started at 10 mg/day and increased to a maximum of 20 mg/day as tolerated. Treatment response was assessed 6–8 weeks after reaching the maximum tolerated dose, with an effective response defined as a ≥25% reduction in Yale Brown Obsessive Compulsive Scale (YBOCS) score. This study was approved by the Ethics Committee of Hyogo Medical University (Approval No. 2080). Results At the beginning of this study, mean age of 35.2 (±10.4) in the PXT group and 33.3 (±11.9) in the ESP group and mean YBOCS total score of 28.8 (±6.7) and 27.6 (±6.6), respectively. The time to achieve the maximum tolerated dose was significantly longer in the PXT group, averaging 7.4 (±4.3) weeks, compared to 4.3 (±4.1) weeks in the ESP group (p < 0.01). In the PXT group, 8 patients (36.4%; 3 at 40 mg/day and 5 at 50 mg/day) showed an effective response, compared to 4 patients (20.0%; all at 20 mg/day) in the ESP group without statistically significant group-difference. Finally, 4 patients (18.2%) in the PXT group discontinued treatment due to side effects, while 5 patients (25.0%) in the ESP group discontinued. Discussion & Conclusions PXT demonstrated a numerically higher treatment response rate compared to ESP, which may be attributed to its broader dosing range; however, this difference was not statistically significant. PXT’s extended titration schedule, often exceeding five weeks due to outpatient scheduling constraints, may delay therapeutic outcomes in routine clinical practice. In contrast, ESP’s simplified titration schedule allows for quicker evaluations of efficacy and tolerability, although its lower maximum dose may limit its overall effectiveness. These results highlight the need to balance pharmacological properties with practical considerations, such as treatment logistics, adherence and adverse effect, when selecting SSRIs for each OCD individual.