Exposure, D-cycloserine Enhancement, and Functional Magnetic Resonance Imaging (fMRI) in Snake Phobics

Study Overview
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Brief Summary
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The aim of the present study is to determine whether people receiving d-cycloserine and exposure therapy show different brain reactions to symptom provocation compared to people receiving placebo and exposure therapy.

Detailed Description
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D-cycloserine (DCS) is a partial N-methyl-D-aspartate (NMDA) receptor agonist that may improve or accelerate extinction learning. We will randomly assign people with snake phobia to receive DCS or placebo, and then provide all participants with exposure therapy. We will examine whether people receiving DCS and vs. placebo show different brain reactions to symptom provocation before and after exposure therapy.

Official Title
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Exposure, D-cycloserine Enhancement, and Functional Magnetic Resonance Imaging (fMRI) in Snake Phobics

Conditions
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Specific Phobia

Intervention / Treatment
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* Drug: D-cycloserine
* Behavioral: Exposure therapy
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Primary diagnosis of specific phobia (snakes) Exclusion Criteria: History of psychosis, obsessive-compulsive disorder, or mania Recent substance abuse or suicidality Previous receipt of study treatments

Ages Eligible for Study
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Minimum Age: 18 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: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: D-cycloserine plus exposure therapy<br>Single session (up to 3 hr) of in vivo exposure therapy plus 50 mg oral d-cycloserine administered 1 hr prior to exposure therapy session | Drug: D-cycloserine<br>* 50 mg d-cycloserine, oral, 1 dose<br>Behavioral: Exposure therapy<br>* Single session graded in vivo exposure therapy, 60-180 minutes<br>|
| Placebo Comparator: Placebo plus exposure therapy<br>Single session (up to 3 hr) of in vivo exposure therapy plus oral placebo capsule administered 1 hr prior to exposure therapy session | Behavioral: Exposure therapy<br>* Single session graded in vivo exposure therapy, 60-180 minutes<br>Drug: Placebo<br>* Single capsule of oral placebo, administered once 1 hr prior to exposure therapy<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Snake Questionnaire (SNAQ) | 30-item self-report scale of severity of snake fear and avoidance Range: 0-30; higher values indicate greater fear severity | 2 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinician's Global Impression (CGI)-Severity | Clinician rating of global illness severity (at pre- and post-treatment) CGI-Severity range 1-7; higher scores indicate greater illness severity. | 2 weeks | 
| Clinician's Global Impression (CGI)-Improvement | Clinician rating of global illness severity (at post-treatment) CGI-Improvement range 1-7; higher scores indicate poorer improvement; classified as responder if score = 1 or 2, nonresponder if score > 2 | 2 weeks |