A clinically significant response to endoxifen in compulsive buying behavior emerging in a patient with long-standing obsessive-compulsive disorder

Compulsive buying behavior (CBB) is increasingly recognized as a disabling impulse-control pathology often underdiagnosed in clinical psychiatry. Although commonly associated with mood disorders and behavioral addictions, its occurrence as a secondary symptom in long-standing obsessive-compulsive disorder (OCD) presents diagnostic and therapeutic challenges. We describe a 45-year-old male with a 20-year history of OCD who developed persistent, distressing online compulsive buying over the past year, causing substantial financial strain despite belonging to an upper socioeconomic background. Conventional strategies, including sodium valproate and oxcarbazepine, yielded no clinical benefit. Introduction of endoxifen 8 mg/day led to a rapid and marked reduction in buying urges within 10 days. Objective improvement was captured using the modified compulsive buying scale (MCBS), which decreased from 42 at baseline to 14 after 1 month of treatment. This report highlights a novel therapeutic response to endoxifen in CBB co-morbid with OCD, suggesting a potential serotonergic-modulating role for endoxifen in impulse-control phenomena. Further systematic research is warranted.