To examine, in a post-hoc, integrated analysis, the first-dose success, cumulative success by dose, and maintenance of success among men taking tadalafil. Early treatment success is important to men with erectile dysfunction.

In five double-blind, placebo-controlled, 12-week studies, men were randomized to placebo (n = 308), tadalafil 10 mg (n = 321), or tadalafil 20 mg (n = 258) as a fixed dose. The Sexual Encounter Profile (SEP) diary questions assessed success from three perspectives: (a) first-dose success; (b) cumulative proportion of men with first success by dose; and (c) maintenance of success among men with first-dose success.

With the first dose, significantly greater proportions of men taking tadalafil 10 and 20 mg versus placebo achieved successful erection (SEP-Q1: 85% and 90% versus 66%, respectively), successful penetration (SEP-Q2: 74% and 79% versus 47%, respectively), successful intercourse (SEP-Q3: 56% and 67% versus 31%, respectively), and were satisfied overall with their sexual experience (SEP-Q5: 36% and 47% versus 15%, respectively; all P <0.001). The proportion of men achieving first success increased with continued dosing, reaching a plateau between doses 4 and 8 at approximately 95% (SEP-Q2), 90% (SEP-Q3), and 81% (SEP-Q5). For men with first-dose success, the subsequent success rate during the 12-week period was significantly greater for men taking tadalafil 10 and 20 mg versus placebo (all P <0.001; SEP-Q2: 85% and 91% versus 75%; and SEP-Q3: 81% and 88% versus 64%, respectively).

Most men taking tadalafil achieved successful erection, penetration, and intercourse after one dose and maintained the success over time. Because success increased with continued use, men who do not respond initially should continue treatment to increase the likelihood of treatment success.