Oral phosphodiesterase type 5 (PDE5) inhibitor therapy is recommended in guidelines as first-line therapy for erectile dysfunction because of its convenience, high efficacy and low rates of side effects. Tadalafil (Cialis, Lilly ICOS, USA), recently approved in Canada and the United States as an oral therapy for erectile dysfunction, has a half-life of 17.5 h, which offers men a longer period of effectiveness than other PDE5 inhibitors. Five randomized, double-blind, placebocontrolled, multicentre trials (four with patients in Canada) studied tadalafil at fixed doses of 2.5, 5, 10, or 20 mg. In an integrated analysis, tadalafil gave statistically significant improvements in all efficacy outcomes compared with placebo. A global assessment question found 81% of men taking tadalafil 20 mg reported overall improvement in their erections. In a separate study, tadalafil significantly improved erectile function 36 h after dosing. Tadalafil has been generally well-tolerated, with side effects comparable to those seen with other PDE5 inhibitors.
