Safety & Efficacy Study Using Topiramate in Posttraumatic Stress Disorder

Inclusion Criteria: * PTSD as defined by DSM-IV for at least 6 months supported by the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I); * Subjects must have a minimum past week CAPS score of \> than 50 at Visit 2; * Subjects must be in general good health as confirmed by medical history, and physical examination; * Subjects must be off prohibited medications for washout periods as outlined under Concomitant Therapy section; * Subjects must have negative urine drug screen (phencyclidine, cocaine, amphetamines, tetrahydrocannabinol, and opiates) at visit 1; * Subjects must either be postmenopausal for at least 1 year,have had a hysterectomy or tubal ligation, be otherwise incapable of pregnancy or have practiced one of the following methods of contraception for at least one month prior to enrollment: hormonal contraceptives, spermicide and barrier, intrauterine device, spousal/partner sterility or be practicing abstinence and agree to continue abstinence or to use an acceptable method of contraception (as listed above) should sexual activity commence. * Subjects must be able to take oral medication, adhere to medication regiments and be willing to return for regular visits; * After full explanation of the study, subjects must demonstrate their willingness to participate by signing an informed consent form. Exclusion Criteria: * Subjects who have a DSM-IV diagnosis of substance dependence or abuse (with the exception of nicotine or caffeine dependence) within the past 3 months; * Subjects with current or past history of primary major depressive disorder or primary major anxiety disorder (i.e. panic disorder, obsessive-compulsive disorder, social phobia) as defined by DSM-IV; * Subjects with current or lifetime history of schizophrenia, bipolar disorder, or other psychotic disorder; * Subjects with diagnosis of current organic mental disorder, factitious disorder or malingering * Subjects with diagnosis of bulimia or anorexia nervosa; * Subjects who are currently enrolled in cognitive-behavioral therapy; * Subjects with current disability compensation or claim pending for persisting functional impairment related to PTSD; * Subjects with prior non-response to topiramate for the treatment of PTSD following an adequate trial. * Subjects who have previously been treated with topiramate and discontinued treatment due to an adverse event or subjects with a known hypersensitivity to topiramate; * Subjects with clinically unstable disease: cardiovascular, renal, gastrointestinal, pulmonary, metabolic, endocrine or other systemic disease that could interfere with their participation in the study; * Subjects with history of nephrolithiasis; * Subjects with SGOT and/or SGPT levels greater than 2 times the upper limit of normal range at screening; * Subjects taking antipsychotics within 3 months of the screening visit; * Subjects with progressive or degenerative neurologic disorders (e.g. multiple sclerosis); * Subjects with active liver disease; * Subjects with estimated creatinine clearance \< 60 mL/min; * Subjects with known clinically significant medical conditions, including but not limited to: symptomatic coronary artery or peripheral vascular disease, malignancy within the past 5 years, except basal cell carcinoma; any condition compromising the function of those body systems that could result in altered absorption, excess accumulation or impaired metabolism or excretion of topiramate; subjects with history of attempted suicide/homicide in the past 12 months or suicidal/homicidal tendencies or judged clinically to be at serious suicidal/homicidal risk; * Subjects who are pregnant or lactating; * Subjects who have not observed the designated washout periods for any of the prohibited medications outline in this protocol; * Subjects who in the opinion of the investigator should not be enrolled in the study because of the Precautions, Warnings, or Contraindications of the topiramate package insert.