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.

Study Overview

• Status: Recruiting
• Conditions: Obsessive-Compulsive Disorder; Body Dysmorphic Disorders; Illness Anxiety Disorder; Somatic Symptom Disorder
• Intervention / Treatment: Drug: Fluoxetine; Drug: Dextromethorphan

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Alessa Gaeta, BA; Phone Number: 650 497 2578; Email: ocdresearch@stanford.edu

Study Locations

• United States
  • California
    • Stanford, California, United States, 94304
      • Recruiting
      • Stanford University
      • Principal Investigator: Peter van Roessel, MD, PhD
      • Contact: Alessa Gaeta, BA; Phone Number: 650-723-4095; Email: ocdresearch@stanford.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Group A: fluoxetine then fluoxetine plus dextromethorphan; Group A participants will take fluoxetine 20mg (or prior dose) daily for 4 weeks, and will then continue fluoxetine while adding over the counter dextromethorphan, with doses increasing weekly as tolerated, for 4 weeks.	Drug: Fluoxetine; Fluoxetine 20mg (or previously prescribed dose) will be taken once daily by mouth for 8 weeks; Other Names: Prozac; Drug: Dextromethorphan; Dextromethorphan, an over-the-counter cough suppressant, will be taken by mouth twice daily for four weeks of the study, starting at 15mg per dose, and increasing weekly as tolerated to a maximum of 60mg per dose.
Experimental: Group B: fluoxetine plus dextromethorphan then fluoxetine; Group B participants will take fluoxetine 20mg (or prior dose) daily together with over the counter dextromethorphan, with doses increasing weekly as tolerated, for 4 weeks, and then will stop dextromethorphan, continuing fluoxetine alone for 4 weeks.	Drug: Fluoxetine; Fluoxetine 20mg (or previously prescribed dose) will be taken once daily by mouth for 8 weeks; Other Names: Prozac; Drug: Dextromethorphan; Dextromethorphan, an over-the-counter cough suppressant, will be taken by mouth twice daily for four weeks of the study, starting at 15mg per dose, and increasing weekly as tolerated to a maximum of 60mg per dose.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Improvement in OCD or related disorder symptoms as measured by the Y-BOCS	Improvement in OCD severity is measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), a gold standard measure of the severity of obsessions and compulsions. Variants of the Y-BOCS designed for assessment of body dysmorphic disorder or illness anxiety disorder/somatic symptom disorder will be used as appropriate. Y-BOCS scores range from 0 to 40, with higher scores indicating greater severity of symptoms. Response will be defined as a 35% reduction in Y-BOCS score.	Change from baseline will be assessed at 4 weeks and at 8 weeks.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Improvement in clinical insight as measured by the BABS	Improvement in clinical insight is measured by the Brown Assessment of Beliefs Scale (BABS), a scale assessing multiple dimensions of clinical insight as relevant to OCD and related disorders. The BABS rates multiple dimensions of clinical insight related to an identified belief. BABS scores range from 0-24, with higher scores indicating greater insight impairment. Response will be defined as a 35% reduction in BABS score.	Change from baseline will be assessed at 4 weeks and at 8 weeks.

Collaborators and Investigators

• Sponsor: Stanford University
• Collaborators: Avy L. & Roberta L. Miller Foundation
• Investigators: Principal Investigator: Peter J van Roessel, MD PhD, Stanford University

Study record dates

Study Major Dates

• Study Start (Actual): January 20, 2022
• Primary Completion (Estimated): April 1, 2027
• Study Completion (Estimated): December 1, 2028

Study Registration Dates

• First Submitted: May 13, 2021
• First Submitted That Met QC Criteria: May 20, 2021
• First Posted (Actual): May 24, 2021

Study Record Updates

• Last Update Posted (Actual): May 20, 2026
• Last Update Submitted That Met QC Criteria: May 18, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: OCD; Fluoxetine; Dextromethorphan; IAD; BDD; SSD
• Additional Relevant MeSH Terms: Mental Disorders; Anxiety Disorders; Somatoform Disorders; Obsessive-Compulsive Disorder; Body Dysmorphic Disorders; Organic Chemicals; Heterocyclic Compounds; Heterocyclic Compounds, Fused-Ring; Alkaloids; Polycyclic Aromatic Hydrocarbons; Polycyclic Compounds; Amines; Heterocyclic Compounds, 4 or More Rings; Morphinans; Opiate Alkaloids; Heterocyclic Compounds, Bridged-Ring; Phenanthrenes; Propylamines; Fluoxetine; Dextromethorphan
• Other Study ID Numbers: 60569

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes