• erectile dysfunction;
  • sildenafil citrate;
  • tadalafil;
  • phosphodiesterase 5 inhibitor

Associate Editor

Michael G. Wylie

Editorial Board

Ian Eardley, UK

Jean Fourcroy, USA

Sidney Glina, Brazil

Julia Heiman, USA

Chris McMahon, Australia

Bob Millar, UK

Alvaro Morales, Canada

Michael Perelman, USA

Marcel Waldinger, Netherlands


To compare treatment preference, efficacy, and tolerability of sildenafil citrate (sildenafil) and tadalafil for treating erectile dysfunction (ED) in men naïve to phosphodiesterase 5 (PDE5) inhibitor therapy.


This was an open-label, crossover study of sildenafil and tadalafil (taken as needed). After a 4-week baseline assessment, 367 men with ED (mean age 54 years) were randomized to receive sildenafil for 12 weeks followed by tadalafil for 12 weeks or vice versa (8-week dose optimization and 4-week assessment phases). During dose optimization, patients started taking 25- or 50-mg sildenafil or 10-mg tadalafil and could titrate to find their optimum dose (25-, 50- or 100-mg sildenafil; 10- or 20-mg tadalafil). After completing both 12-week periods, patients chose which treatment to continue during an 8-week extension. Efficacy was measured with the International Index of Erectile Function (IIEF) and Sexual Encounter Profile (SEP) diary.


Of the 291 men who completed both treatments, 85 (29%) chose sildenafil and 206 (71%) chose tadalafil (P < 0.001) for the 8-week extension. The IIEF erectile function domain scores were 14.2 at baseline, 23.9 at endpoint on sildenafil, and 24.3 at endpoint on tadalafil (P = 0.08, sildenafil vs tadalafil). The mean per patient percentage success scores for SEP2 (penetration) were: baseline (46%), sildenafil (post-baseline 82%) and tadalafil (post-baseline 85%; P = 0.06, sildenafil vs tadalafil), and for SEP3 (successful intercourse) were: baseline (19%), sildenafil (post-baseline 72%), and tadalafil (post-baseline 77%; P = 0.003, sildenafil vs tadalafil). The only treatment-emergent adverse events that were reported by >5% of men were headache and flushing.


In men with ED who were naïve to PDE5 inhibitor therapy, sildenafil and tadalafil were both effective and well tolerated. After treatment with sildenafil and tadalafil, 29% of men chose sildenafil and 71% chose tadalafil for ED therapy during an 8-week extension.