This study investigates the safety, tolerability and pharmacokinetics of PF-04191834 when respectively given orally as a single dispersion dose and a single dose of a suspension. The suspension is the test formulation and the dispersion is the formulation with which the novel preparation will be compared.

Inclusion Criteria:

• Healthy male and/or female subjects of non-childbearing potential between the ages of 18 and 55 years, inclusive. Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history, full physical examination, including blood pressure and pulse rate measurement, 12-lead ECG or clinical laboratory tests.
• Body Mass Index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg(110 lbs).

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
• Clinical evidence of existing hepatic disease or a medical history of such a condition in the last year. Subjects with AST or ALT >ULN. Subjects with total bilirubin >ULN (except those with a documented history of Gilbert's Syndrome). Subjects with AST/ALT/total bilirubin >ULN and <1.5X ULN may be retested once.
• Treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) preceding the first dose of study medication;
• Use of tobacco- or nicotine-containing products in excess of the equivalent of 5 cigarettes per day;
• Females of childbearing potential.
• Subjects with positive responses (score 1) for suicidality on the Sheehan Suicidality Tracking Scale (S-STS) (specifically items 1a, 1b, 3, 4, 5, 6, 7, or 9).