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).
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
Develop blood pressure lowering or experience dizziness, lightheadedness when going from
the laying down position to standing position.