Hatzichristou · European urology 2005 · prospective case series · n=100

Sildenafil failures may be due to inadequate patient instructions and follow-up: a study on 100 non-responders.

Cited 98 times in the scientific literature.

Level 4 - case-series / case-control

Uncontrolled prospective case series

PubMed 15774252 · doi:10.1016/j.eururo.2004.12.005 · record verified 2026-08-27

What was done

The study evaluated 100 consecutive patients (mean age 59 +- 14.4 years, mean erectile dysfunction duration 5.5 +- 6.4 years) presenting as sildenafil non-responders. Participants completed the International Index of Erectile Function (IIEF) and a questionnaire regarding their prior sildenafil use and instructions received. When inappropriate use was reported, patients received corrective instructions on proper administration, timing, and dosing, and were instructed to try at least 4 tablets at home before efficacy was re-evaluated at a scheduled follow-up visit.

What was found

Baseline mean IIEF erectile function domain score was 14 +- 9.9. Inappropriate use was identified in 56 of 100 patients: 45 had never tried the 100 mg dose, 32 took the pill on a full stomach right after a meal, 22 took it immediately before sexual activity, and 12 did not know sexual stimulation was required. In addition, 8 patients used 100 mg despite factors reducing drug clearance, and only 34 patients had a follow-up scheduled by their original physician. After proper education and dose titration, 31 patients responded to sildenafil (10 at 50 mg and 21 at 100 mg).

Why it matters

Apparent sildenafil failure often stems from correctable errors in administration or lack of dose escalation rather than true pharmacologic resistance. Re-educating patients on proper use can salvage successful response in nearly one-third of non-responders before advancing to more invasive treatments.

Limits

This was a single-arm, uncontrolled observational case series with no comparator group. Prior medication use and physician instructions relied on retrospective patient recall, and the abstract does not report long-term follow-up or the specific criteria used to define treatment response.

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