Study of Dextromethorphan in OCD and Related Disorders

Fluoxetine/Dextromethorphan in Obsessive-Compulsive and Related Disorders: an Open-Label Crossover Pilot Study

The purpose of the study is to assess the tolerability and efficacy of dextromethorphan in combination with fluoxetine for symptom relief in OCD and related disorders.

Obsessive compulsive disorder (OCD) and the related disorders body dysmorphic disorder (BDD), somatic symptom disorder (SSD) and illness anxiety disorder (IAD) are psychiatric conditions characterized by recurrent, intrusive thoughts, feelings or images (obsessions or preoccupations) and repetitive or ritualized behaviors or avoidance performed to relieve obsession or preoccupation-related anxiety. They are a significant cause of mental health-related disability, and are inadequately served by available treatments.

This study tests whether an over-the-counter cough suppressant medicine, dextromethorphan, may offer symptom relief when combined with a low dose of fluoxetine, a standard prescription treatment for OCD and related disorders.

Inclusion Criteria:

• Diagnosis of obsessive-compulsive disorder (OCD), body dysmorphic disorder (BDD), illness anxiety disorder (IAD) or somatic symptom disorder (SSD)
• Living within California
• Capacity to provide informed consent

Exclusion Criteria:

• Current bipolar disorder or psychotic disorder
• Active moderate or severe substance use disorder, lifetime severe substance use disorder
• Pregnant or nursing women
• Use of prescribed psychotropic medications other than fluoxetine for 2 weeks prior to study start
• Having commenced OCD-targeted exposure and response-prevention (ExRP) psychotherapy within 2 months of study start