A Study to Compare the Blood Levels of Sildenafil Following Administration of an Experimental Tablet vs. the Conventional Oral Tablet in Healthy Subjects

Inclusion Criteria: * Healthy males between the ages of 18 and 55 years. * Body Mass Index of 18 to 30 kg/m2, and a total body weight \>50 kg (110 lbs). Exclusion Criteria: * Smoking in excess of the equivalent of 5 cigarettes per day. * Treatment with an experimental drug within 30 days or sildenafil, vardenafil, tadalfil within 4 days before first study dose. * Develop blood pressure lowering or experience dizziness, lightheadedness when going from the laying down position to standing position.