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Porst H, Giuliano F, Glina S, Ralph D, Casabe AR, Elion-Mboussa A, Shen W, Whitaker JS. Evaluation of the Efficacy and Safety of Once-a-Day Dosing of Tadalafil 5mg and 10 mg in the Treatment of Erectile Dysfunction: Results of a Multicenter, Randomized, Double-Blind, Placebo-Controlled Trial. Eur Urol 2006;50:351-359.

The first line in the medical management of erectile dysfunction (ED) is an on demand oral phosphodiesterase-5 (PDE-5) inhibitor. Once daily or alternate daily dosing has been compared to an on demand PDE-5 inhibitor but not with a placebo. Tadalafil with its 17.5 hours half-life makes it suitable for this purpose with a steady state being achieved in 5 days. Here we have a multicenter, randomised, double blind, placebo controlled, parallel-group study looking at 5mg and 10mg tadalafil.

268 men aged 18+ with at least a 3 month history of ED were categorised into 3 groups depending on International Index of Erectile Dysfunction (IIEF) score (1-10 severe, 11-17 moderate, 18-30 mild). As patients were enrolled based on history those with IIEF scores 26-30 (“no ED”) were still included. They were randomised to receive placebo, 5mg tadalafil or 10mg tadalafil in ratio 1:2:2 for 12 weeks. Efficacy was assessed using IEFF, Sexual Encounter Profile (SEP) diary and Global Assessment Questionnaire (GAQ).

This study concludes that once daily dosing with either tadalafil 5mg or 10mg is a well tolerated option and significantly improved erectile function in men with ED. All published parameters were significant (P<0.001) when compared with placebo with respective changes (placebo, tadalafil 5mg, tadalafil 10mg) in IIEF score of 0.9, 9.7, 9.4, SEP2 11.2, 36.5, 39.4 and SEP3 13.2, 45.5, 50.1. Percentage of those reporting “no ED” at the end of the study was 8.3%, 51.5%, 50.5% and improvement 28.3%, 84.5%, 84.6%. Dyspepsia, headache, back pain, upper abdominal pain and myalgia occurred in at least 5% of patients with 9 (3.4%) patients discontinuing because of adverse events (1 placebo, 2 tadalafil 5mg, 6 tadalafil 10mg). One patient died in the tadalafil group but this was related to renal cell carcinoma rather than the tadalafil in the investigators opinion. Although not recorded as significant there does appear to be an increase in withdrawals in the tadalafil 10mg group due to adverse events and this dose may not be tolerated quite so well.