The hypothesis for the trial is that the Sildenafil Citrate Powder for Oral Suspension (10 Mg/ml) bioequivalent to the Revatio 20 Mg IR tablet in Healthy Volunteers and the Sildenafil Citrate 10 Mg immediate release (IR) tablet is bioequivalent to the Revatio 20 Mg IR tablet in Healthy Volunteers.

Inclusion Criteria:

1) Healthy male/female subjects 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 and clinical laboratory tests.

2. Body Mass Index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lbs).

3. An informed consent document signed and dated by the subject or a legally acceptable representative.

4. Subjects who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, and other study procedures.

Exclusion Criteria:

1. Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, ocular or allergic (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing) disease or clinical findings at Screening.
2. History of febrile illness within 5 days prior to the first dose.
3. A positive urine drug screen.