An open-label, multicentre, randomized, crossover study comparing sildenafil citrate and tadalafil for treating erectile dysfunction in men naïve to phosphodiesterase 5 inhibitor therapy.

OBJECTIVES: 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.

PATIENTS AND METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.