A Randomized, Open-Label, Crossover, Multicenter, Single Dose Comparator Study Evaluating Onset Of Penile Rigidity In Men With Erectile Dysfunction Who Are Treated With Sildenafil And Tadalafil

Inclusion Criteria: * Included subjects were 18 years of age or older * A clinical diagnosis of erectile dysfunction * Known responders to either 100 mg sildenafil or 20 mg tadalafil. Exclusion Criteria: * Excluded were subjects who were unable to achieve penile rigidity of greater than or equal to 20% at the base of the penis that was sustained for at least 3 minutes * Subjects who are able to achieve penile rigidity of greater than or equal to 60% at the base of the penis that was sustained for for at least 2 minutes or subjects who are able to achieve penile rigidity of greater than or equal to 80% at the base of the penis that is sustained for for at least 1 minute measured by Rigiscan®, at screening with no therapy, within 60 minutes following visual sexual stimulation * Subjects currently using any commercially available treatments for erectile dysfunction * Subjects on nitrates.