The ENDOTRIAL Study: A Spontaneous, Open-Label, Randomized, Multicenter, Crossover Study on the Efficacy of Sildenafil, Tadalafil, and Vardenafil in the Treatment of Erectile Dysfunction


  • The ENDOTRIAL STUDY GROUP: Eleonora Carosa, Silvia Di Tommaso (University of L'Aquila), Roberto Bruzziches, Davide Francomano, Daniele Gianfrilli, Carlotta Pozza, Elisa Giannetta (University of Rome “La Sapienza”), Riccardo Selice, Nicola Caretta (University of Padua), Francesca Paggi, Eddi Buldreghini (University of Ancona), Angela Magini, Csilla Krausz (University of Florence), Massimiliano Caprio, Massimo Ulderico De Martino, Stefania Falcone, Alessandra Ruggiero (University of Rome “Tor Vergata”), Alessandro Guidi, Giovanni De Mola, Valeria Pugni (University of Modena and Reggio Emilia).

Emmanuele Jannini, MD, Department of Experimental Medicine, University of L'Aquila, Via Vetoio, Coppito, L'Aquila 67100, Italy. Tel: +39 (0) 433530; Fax: +39 (0) 433523; E-mail:;


Introduction.  The three effective, commercially available drugs for the treatment of erectile dysfunction—sildenafil, vardenafil, and tadalafil—inhibit the same substrate, the erectolytic enzyme phosphodiesterase type 5 (PDE5). Although there are pharmacological differences between these three compounds, few comparative studies have been conducted to date.

Aim.  The aim of this study was to determine the efficacy of sildenafil, tadalafil, and vardenafil in a randomly assigned 8-week fixed regimen.

Methods.  This was a spontaneous, open-label, randomized, multicenter, crossover study where the patients were randomized to receive sildenafil 50 mg, sildenafil 100 mg, tadalafil 20 mg, or vardenafil 20 mg.

Main Outcome Measures.  The primary outcome included the posttreatment analysis of erectile function domains of the abridged International Index of Erectile Function (IIEF5+1). The secondary objectives included the analysis of peak-systolic velocities (PSVs), end-diastolic velocities (EDVs), and resistive index (RI), and the estimate of the percentage of men with normal penile hemodynamic parameters after each treatment.

Results.  In all groups of patients taking sildenafil 50 mg, sildenafil 100 mg, tadalafil 20 mg, and vardenafil 20 mg at a frequency reflecting the common treatment regimens in real life, there was a statistically significant baseline-to-end point improvement in subjective perception of erectile function measured by IIEF5+1. When the four groups were compared, the treatments were not different in modifying IIEF5+1 and penile flow parameters. However, the within-group analysis showed that PSV improved in the sildenafil 50 mg group and that PSV together with RI significantly ameliorated in patients receiving 100 mg of sildenafil. Regression analysis confirmed an independent effect of sildenafil on hemodynamic efficacy parameters.

Conclusions.  An overall equivalence was demonstrated in the subjective perception of treatment benefits for all the PDE5i tested. However, sildenafil, in a dose-dependent manner, was the unique PDE5i able to ameliorate some of the penile flow parameters within the 8-week treatment period. These findings should be interpreted conservatively because of the observational nature of the study. Jannini EA, Isidori AM, Gravina GL, Aversa A, Balercia G, Bocchio M, Boscaro M, Carani C, Corona G, Fabbri A, Foresta C, Forti G, Francavilla S, Granata ARM, Maggi M, Mansani R, Palego P, Spera G, Vetri M, and Lenzi A on behalf of the Endotrial Study Group. The ENDOTRIAL study: A spontaneous, open-label, randomized, multicenter, crossover study on the efficacy of sildenafil, tadalafil, and vardenafil in the treatment of erectile dysfunction. J Sex Med 2009;6:2547–2560.