Fixed Dose Study of PD 0332334 and Paroxetine for the Treatment of Generalized Anxiety Disorder

Inclusion Criteria: Subjects must meet all of the following inclusion criteria to be eligible for enrollment into the study: 1. Diagnosis of generalized anxiety disorder (Diagnostic and Statistical Manual-IV \[DSM-IV\], 300.02) as established by the clinician. 2. Subjects must have a Hamilton-A total score ≥20 at the screening (V1) and randomization (V2) visits. Subjects must also have a Covi Anxiety Scale score of ≥9 and a Raskin Depression Scale score ≤7 at the Screening (V1) visit to ensure predominance of anxiety symptoms over depression symptoms. 3. Otherwise healthy men or non-pregnant, non-lactating women (women must be using a hormonal or barrier method of contraception or be postmenopausal or surgically sterilized). Healthy is defined as no other clinically relevant abnormalities identified by a detailed medical history, full physical examination including sitting blood pressure and heart rate measurement, 12-lead ECG, and clinical laboratory tests. 4. Age 18 to 65 years, inclusive. 5. All women must have negative pregnancy tests at the Screening (Visit 1) and Randomization (Visit 2) visits. 6. Evidence of a personally signed and dated informed consent document indicating that the subject has been informed of all pertinent aspects of the study. 7. Subjects who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures. Exclusion Criteria: Subjects presenting with any of the following will not be included in the study: 1. Subjects with evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, pancreatic, neurologic, active infections, immunological, or allergic disease (including drug allergies). 2. Any of the following current (within the past 6 months through the present) Diagnostic and Statistical Manual of Mental Disorders-IV Axis I diagnoses: * Major depressive disorder; * Obsessive compulsive disorder; * Panic disorder; * Agoraphobia; * Posttraumatic stress disorder; * Anorexia; * Bulimia; * Caffeine-induced anxiety disorder; * Alcohol or substance abuse or dependence unless in full remission for at least 6 months; * Social anxiety disorder. 3. Any of the following past or current Diagnostic and Statistical Manual of Mental Disorders-IV Axis I diagnoses: * Schizophrenia; * Psychotic disorder; * Delirium, dementia, amnestic, and other clinically significant cognitive disorders; * Bipolar or schizoaffective disorder; * Cyclothymic disorder; * Dissociative disorders. 4. Antisocial or borderline personality disorder. 5. Serious suicidal risk per the clinical investigator's judgment. (Note: The Suicidality module of the Mini-Mental State Examination diagnostic interview and the Columbia-Suicide Severity Rating Scale should be used as aids to the assessment of suicidality, but do not replace overall clinical judgment in determination of suicidal risk). 6. Current use of psychotropic medications (ie, drugs normally prescribed for depression, mania, anxiety, insomnia, or psychosis) that cannot be discontinued 2 weeks prior to randomization. Fluoxetine is prohibited within 5 weeks of randomization. In the event of inadvertent administration of psychotropic medications during the 2 weeks prior to randomization, continued eligibility will be assessed on a case by case basis by the investigator and the medical monitor. 7. Use of drugs, supplements, prescription or nonprescription, or food that have psychoactive properties. In the event of inadvertent use of such products during the 2 weeks prior to randomization, continued eligibility will be assessed on a case by case basis by the investigator and the medical monitor. In addition, following a discussion of the individual case between the medical monitor and the investigator, the medical monitor may allow minimal anxiolytic medication (for example a benzodiazepine) use for subjects who experience significant intolerable anxiety during the final week of the study (Days 64-71). 8. Subjects who have been treated with monoamine oxidase inhibitors in the 14 days prior to the baseline visit. 9. Regular use of benzodiazepines during the 3 months prior to Screening (for at least 5 out of 7 days per week). 10. Subjects initiating formal psychotherapy within 3 month prior to screening who intend to continue formal psychotherapy during the study. This includes psychodynamic, cognitive, and interpersonal therapies. 11. Positive drug tests at Screening (Visit 1) or Randomization (Visit 2) visits for any of the following substances or classes of compounds: amphetamines, barbiturates, opiates, benzodiazepines, sedatives and hypnotics, cocaine, phencyclidine (PCP), cannabinoids, or other illegal or illicit drugs. An exception to the exclusion for a positive benzodiazepine, opiate, or sedative and hypnotic drug test at the Screening (Visit 1) visit may be granted by the Pfizer medical monitor if written evidence of a valid, current prescription is presented. 12. Any condition possibly affecting drug absorption (eg, gastrectomy). 13. Subjects with a current seizure disorder. 14. Subjects with a history of life-threatening neoplasms within 5 years prior to study entry, other than carcinoma in situ of the cervix or basal cell carcinoma of the skin. 15. Subjects with hypothyroidism or hyperthyroidism, except subjects who are euthyroid and have been on stable doses of thyroid replacement for 6 months or more. 16. Subjects with any clinically unstable hematological, autoimmune, endocrine, neurological, renal, hepatic, retinal, gastrointestinal, or cardiovascular disorder. 17. Subjects with uncontrolled narrow angle glaucoma. 18. Subjects with a known hypersensitivity to paroxetine. 19. History of allergy or intolerance to paroxetine. 20. Subjects with a prior history of insufficient response to paroxetine in the treatment of generalized anxiety disorder (with an adequate trial of therapy). 21. Pregnant or nursing females; females of childbearing potential who are unwilling or unable to use an acceptable method of contraception for the duration of the study. 22. Treatment with an investigational drug within 60 days preceding the first dose of trial medication. 23. Estimated creatinine clearance \<55 mL/min (using Cockcroft-Gault equation). 24. Alanine aminotransferase or aspartate aminotransferase (AST) levels \>3 times the upper limit of normal at Screening (Visit 1). 25. Male and Female subjects with a screening 12-lead ECG demonstrating QTcF (Fredericia's correction) \>450 msec, if confirmed with an unscheduled repeat 12-lead ECG's at the screen visit. In the event of discrepant QTcF values (i.e., \>450 msec and \<450 msec) after repeat unscheduled 12-lead ECG at screen, a decision with regards protocol eligibility will be made on a case by case basis between the investigator and medical monitor. 26. History of lack of efficacy for treatment of generalized anxiety disorder with, or allergy or intolerance to, other α2δ drugs (pregabalin, gabapentin). 27. Blood donation of approximately 1 pint (500 mL) or more within 56 days prior to dosing. 28. Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with trial participation or investigational product administration or may interfere with the interpretation of trial results and, in the judgment of the investigator, would make the subject inappropriate for entry into this trial.