8-week, single-blind, randomized trial comparing risperidone versus olanzapine augmentation of serotonin reuptake inhibitors in treatment-resistant obsessive–compulsive disorder

The aim of the present pilot study was to investigate in a single-blind manner, over a period of 8 weeks, the comparative efficacy and tolerability of risperidone versus olanzapine addition in the treatment of OCD patients who did not show a ≥ 35% decrease in the YBOCS score after 16-week SRI treatment (defined as resistant). The study consisted of two different phases: a 16-week open-label prospective phase to ascertain resistance to SRI treatment and an 8-week single-blind addition phase for resistant subjects only. Ninety-six subjects with DSM-IV OCD (YBOCS ≥ 16) entered the open-label prospective phase; at the end of the 16-week period, 50 (52%) were judged to be resistant and were randomized to receive risperidone (1 to 3 mg/d) or olanzapine (2.5 to 10 mg/d) addition for 8 weeks. Overall, patients in both groups responded significantly, without differences between the two treatment groups; although no differences emerged for the proportion of patients reporting at least an adverse event, the profiles of adverse experiences differed significantly, being risperidone associated with amenorrhoea and olanzapine with weight gain.