title: Sildenafil, a novel effective oral therapy for male erectile dysfunction.
abstract: OBJECTIVE
  To determine the efficacy and safety of sildenafil, a novel orally active inhibitor of the type-V cyclic guanosine monophosphate-specific phosphodiesterase (the predominant isoenzyme in the human corpus cavernosum) on penile erectile activity in patients with male erectile dysfunction of no established organic cause.
  
  
  METHODS
  Twelve patients (aged 36-63 years) with male erectile dysfunction of no established organic cause were entered into a double-blind, randomized, placebo-controlled, crossover study which was conducted in two phases. In the first phase (four-way crossover), treatment efficacy was evaluated by measurements of penile rigidity using penile plethysmography during visual sexual stimulation at different doses of sildenafil (10, 25 and 50 mg or placebo). In the second phase (two-way crossover), efficacy was assessed by a diary record of penile erectile activity after single daily doses of sildenafil (25 mg) or placebo for 7 days.
  
  
  RESULTS
  The mean (95% confidence interval, CI) duration of rigidity of > 80% at the base of the penis was 1.3 min (0.4-3.1) in patients on placebo, 3.5 min (1.6-7.3; P = 0.009) on 10 mg, 8.0 min (3.7-16.7; P = 0.003) on 25 mg and 11.2 min (5.6-22.3; P < 0.001) on 50 mg of sildenafil. The mean (95% CI) duration of rigidity of > 80% at the tip of the penis was 1.2 min (0.4-2.7) on placebo and 7.4 min (2.4-8.5; P = 0.001) on 50 mg sildenafil. From the diary record of daily erectile activity, the mean (95% CI) total number of erections was significantly higher in patients receiving sildenafil was 6.1 (3.2-11.4), compared with 1.3 (0.5-2.7) in those on placebo; 10 of 12 patients reported improved erectile activity while receiving sildenafil, compared with two of 12 on placebo (P = 0.018). Six patients on active treatment and five on placebo reported mild and transient adverse events which included headache, dyspepsia and pelvic musculo-skeletal pain.
  
  
  CONCLUSIONS
  These results show that sildenafil is a well tolerated and effective oral therapy for male erectile dysfunction with no established organic cause and may represent a new class of peripherally acting drug for the treatment of this condition.
authors.affiliation: Department of Urology, Southmead Hospital, Westbury on Trym, Bristol, UK.
authors.forename: M
authors.initials: M
authors.lastname: Boolell
authors.forename: S
authors.initials: S
authors.lastname: Gepi-Attee
authors.forename: J C
authors.initials: JC
authors.lastname: Gingell
authors.forename: M J
authors.initials: MJ
authors.lastname: Allen
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000284:Administration, Oral; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D007172:Erectile Dysfunction / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D010410:Penile Erection / Q000187:drug effects*; D010879:Piperazines / Q000008:administration & dosage*; D010991:Plethysmography; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate; D015106:3',5'-Cyclic-GMP Phosphodiesterases