Study of Dextromethorphan in OCD and Related Disorders

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

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

Conditions
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Obsessive-Compulsive Disorder, Illness Anxiety Disorder, Body Dysmorphic Disorders, Somatic Symptom Disorder

Intervention / Treatment
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* Drug: Fluoxetine
* Drug: Dextromethorphan


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: After signing consent and baseline assessments, participants will be randomized 1:1 to Group A or Group B for the purposes of sequencing fluoxetine vs combined fluoxetine/dextromethorphan treatment periods.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Group A: fluoxetine then fluoxetine plus dextromethorphan<br>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<br>* Fluoxetine 20mg (or previously prescribed dose) will be taken once daily by mouth for 8 weeks<br>* Other names: Prozac;Drug: Dextromethorphan<br>* 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.<br>|
| Experimental: Group B: fluoxetine plus dextromethorphan then fluoxetine<br>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<br>* Fluoxetine 20mg (or previously prescribed dose) will be taken once daily by mouth for 8 weeks<br>* Other names: Prozac;Drug: Dextromethorphan<br>* 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.<br>|

What is the study measuring?
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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. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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OCD, BDD, IAD, SSD, Fluoxetine, Dextromethorphan