Study to Evaluate Viagra's Ability to Provide a Better Sexual Experience Through Quality Erections and Satisfaction

The study objective is to:

1. To evaluate the effect of sildenafil citrate versus placebo on the IIEF_EF Domain at the end of the double-blind phase
2. To assess the relationship between treatment with sildenafil citrate or placebo and responses to the Quality of Erection Questionnaire (QEQ) and Sexual Experience Questionnaire (SEX_Q).

• Kirby M, Creanga DL, Stecher VJ. Erectile function, erection hardness and tolerability in men treated with sildenafil 100 mg vs. 50 mg for erectile dysfunction. Int J Clin Pract. 2013 Oct;67(10):1034-9. doi: 10.1111/ijcp.12229.
• Claes HIM, Goldstein I, Althof SE, Berner MM, Cappelleri JC, Bushmakin AG, Symonds T, Schnetzler G. Understanding the effects of sildenafil treatment on erection maintenance and erection hardness. J Sex Med. 2010 Jun;7(6):2184-2191. doi: 10.1111/j.1743-6109.2010.01791.x. Epub 2010 Apr 1.
• Loran OB, Ströberg P, Lee SW, Park NC, Kim SW, Tseng LJ, Collins S, Stecher VJ. Sildenafil citrate 100 mg starting dose in men with erectile dysfunction in an international, double-blind, placebo-controlled study: effect on the sexual experience and reducing feelings of anxiety about the next intercourse attempt. J Sex Med. 2009 Oct;6(10):2826-35. doi: 10.1111/j.1743-6109.2009.01428.x.

Inclusion Criteria:

• Male subjects aged 18-65.
• Documented clinical diagnosis of erectile dysfunction confirmed by an IIEF-EF Domain score of less than or equal to 25. (If the subject scores greater than 25 on the IIEF-EF Domain, screening procedures should be terminated.)

Exclusion Criteria:

• Subjects who have been treated with more than 6 doses of sildenafil citrate or any other phosphodiesterase type 5 (PDE-5) inhibitor such as vardenafil or tadalafil for erectile dysfunction [Note: subjects should not have taken any PDE-5 inhibitors within 4 weeks prior to the date of screening].