Enhancing Extinction Learning in Post Traumatic Stress Disorder (PTSD)

The psychotherapy the investigators are offering in this study is a type of cognitive
behavioral therapy called imaginal exposure. In imaginal exposure, the investigators
encourage the client to approach the memory of the trauma by recounting the trauma story to
the therapist and discussing his or her reactions to the memory.

Inclusion Criteria:

1. Current primary PTSD diagnosis based on DSM-IV criteria, with a minimum duration of
12 weeks since the traumatic event.

2. Between the age of 18 and 65.

Exclusion Criteria:

1. Current diagnosis of schizophrenia, delusional disorder, or organic mental disorder
as defined by the DSM-IV.

2. Current diagnosis of bipolar disorder, depression with psychotic features, or
depression severe enough to require immediate psychiatric treatment (i.e., serious
suicide risk with intent and plan).

3. Current diagnosis of alcohol or substance dependence within the 3 previous months.

4. Unwilling or unable to discontinue current trauma-focused psychotherapy or
psychotropic medication (at least 1 month medication free).

5. Ongoing intimate relationship with the perpetrator (in assault-related PTSD cases).

6. Unstable cardiovascular, autoimmune, endocrine, neurological, renal, hepatic,
retinal, gastrointestinal, or hematological disorder or current seizure disorder.

7. Pregnant or nursing females; females of childbearing potential who are unwilling or
unable to use an acceptable method of contraception for the duration of active
treatment.

8. A history of hypersensitivity or allergy to MB.

9. Any condition possibly affecting drug absorption (e.g., gastrectomy).

10. Glucose-6-phosphate dehydrogenase deficiency.

11. Other severe acute or chronic medical or psychiatric condition or laboratory
abnormality that, in the judgment of the Medical Directors, would make the
participant inappropriate for entry.