A Study to Investigate the Effects on Blood Pressure and Pulse Rate of a Single 100mg Dose of Sildenafil in Patients With Benign Prostatic Hyperplasia Who Are Being Treated With Doxazosin

• Drug: placebo
  
  placebo by mouth as a single dose
• Drug: sildenafil
  
  sildenafil 100 mg by mouth as a single dose

• Active Comparator: Arm 1
  
  Intervention: Drug: sildenafil
• Placebo Comparator: Arm 2
  
  Intervention: Drug: placebo

Inclusion Criteria:

• patients who weighed between 132 and 220 lb (60 and 100 kg) with benign prostatic hyperplasia (BPH)
• a total PSA (prostate specific antigen) measurement of less than or equal to 10 µg/L within the 12 months prior to screening, were currently on doxazosin treatment for BPH, had been treated with doxazosin for a minimum of 2 months prior to first dose of study medication, and had received a minimum of 4 mg doxazosin once daily (from doxazosin supplied for this study) for 2 weeks prior to the first dose of study medication.

Exclusion Criteria:

• subjects with a recent history (i.e. within 6 months prior to screening) of stroke or myocardial infarction
• subjects with severe cardiovascular disorders such as unstable angina or severe congestive heart failure
• subjects with known hereditary degenerative retinal disorders, such as retinitis pigmentosa
• subjects with a supine systolic/diastolic blood pressure of >170/100 mmHg or <100/60 mmHg either at screening or at the pre-dose measurements
• subjects receiving any other antihypertensive therapy other than doxazosin in the 3 weeks prior to the first dose of study medication.