• Psychological Assessment of Sexual Dysfunction;
  • Pharmacological Studies in Sexual Function;
  • Male Erectile Disorder


Objectives.  Tadalafil, a phosphodiesterase type 5 inhibitor, has an extended period of effectiveness, up to 36 hours, for the treatment of erectile dysfunction (ED). Changes in behavior of long-term sildenafil users were evaluated by assessing time of dose relative to sexual intercourse attempts during treatment with sildenafil and tadalafil.

Materials and Methods.  This open-label study was conducted in men with ED and a history of ≥6-week prior sildenafil use in Australia, New Zealand, Asia, Central and Eastern Europe, the Middle East, and Latin America. Patients continued sildenafil treatment for 4 weeks, then switched to tadalafil for 8 weeks. Timing of sexual intercourse attempt relative to dose was assessed through patient diaries for the final 4 weeks of each treatment period. Patients continued their treatment of choice in an extension period.

Results.  A total of 2,760 men (mean age 54.4 years) with a median duration of prior sildenafil use of 474 days were enrolled. Significant increases in median time from dose to intercourse attempt were observed when changing treatment from sildenafil citrate (1.21 hours) to tadalafil (3.25 hours; P < 0.001). Fifty-nine percent of intercourse attempts were within 4 hours of dosing when patients were treated with tadalafil (88% with sildenafil). The proportion of intercourse attempts per patient made >4 hours after dose was considerably higher during the tadalafil than during the sildenafil assessment period. Similar daily cycles of frequency of dosing and intercourse attempts were observed in all study periods and were characterized by a small peak in the morning and a large peak in the evening. When changing treatment to tadalafil, patients administered the drug earlier in the day and over a broader period of time.

Conclusion.  Following the dosing instructions reflecting tadalafil's extended period of effectiveness, men with a history of established sildenafil use changed their dose-attempt behavior when treated with tadalafil. Glina S, Sotomayor M, Gatchalian E, Yaman O, Dyachkova Y, Markey C, and V Kopernicky. Timing of dose relative to sexual intercourse attempt in previous sildenafil citrate users treated with tadalafil. J Sex Med 2006;3:309–319.