The development of phosphodiesterase inhibitors, which are selective for the type 5 isoenzyme, has revolutionized the initial evaluation and treatment of men with erectile dysfunction. These agents can be taken orally and are effective in 60-70% of patients with erectile dysfunction, and they have low incidences of side effects when taken as recommended. The major contraindications are concomitant use with nitrates or the alpha-blockers terazosin and doxazosin. The major difference in the three approved inhibitors is that tadalafil has a considerably longer serum half-life, which provides a longer window of opportunity and potentially side effects.
