Comparing the efficacy of ondansetron and granisetron augmentation in treatment-resistant obsessive-compulsive disorder: a randomized double-blind placebo-controlled study

This study aimed to assess the efficacy and tolerability of ondansetron vs. granisetron in patients with treatment-resistant obsessive-compulsive disorder. A randomized clinical trial conducted on 135 patients with a Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) diagnosis of obsessive-compulsive disorder, who were treatment-resistant and receiving stable treatment with selective serotonin reuptake inhibitors and antipsychotic, received 14 weeks (phase I, intervention period) of placebo (n = 45), ondansetron (n = 45, 4 mg), and granisetron (n = 45, 2 mg) daily augmentations. Patients were rated every 2 weeks using the Yale-Brown Obsessive Compulsive Scale. Upon completion of intervention course, patients were followed for 4 weeks (phase II, discontinuation period). The collected data were analyzed in SPSS Version 22, with chi(2) test; Fisher's exact test and independent t-test, according to the intention-to-treat principle. Two-factor repeated measure analysis of variance was used to compare score changes over phases. P < 0.05 was considered to be statistically significant. At week 14, reduction in Yale-Brown Obsessive Compulsive Scale scores in ondansetron, granisetron and placebo groups was 41.5%, 39.7% and 15.2%, respectively (P = 0.001). Complete response in the ondansetron group was significantly higher than in the granisetron group ((P = 0.041), risk ratio (95% confidence interval) = 2.33 (1.18-3.045)]. Relapse occurred by three (7.31%) patients in the granisetron group, whereas it was not seen in the ondansetron group [P < 0.001, risk ratio (95% confidence interval) = 2.81 (1.016-4.51)]. The results of this present study confirm the benefit of using ondansetron and granisetron as augmenting agents in treatment-resistant obsessive-compulsive disorder. Our results supported the potential superiority of ondansetron compared to granisetron. This needs to be confirmed in further placebo-controlled augmentation studies.