10.1177/0897190004269201 ARTICLENORWOOD ET ALADVANCES IN THE TREATMENT OF ERECTILE DYSFUNCTION Advances in the Treatment of Erectile Dysfunction

Erectile dysfunction (ED) affects more than 150 million men and their partners throughout the world. Sildenafil, the first oral phosphodiesterase-type 5 (PDE-5) inhibitor approved for the treatment of ED, has led to the discovery of 2 more prod-ucts in this class, with tadalafil being the latest. Tadalafil has proven to be well tolerated in various clinical studies and has demonstrated effectiveness in men with mild to severe ED, re-gardless of severity, etiology, or age. One major characteristic that may distinguish tadalafil from other oral PDE-5 inhibi-tors is its extensive duration of effect. Tadalafil has a thera-peutic duration of up to 36 hours that may allow patients to engage in sexual activity at their own convenience rather than in a limited time period. This, along with other clinical and practical advantages, should make tadalafil an attrac-tive alternative to currently available treatments options. This article summarizes the pharmacology, pharmacokinetics, adverse effects, and clinical efficacy of tadalafil. KEY WORDS: Erectile dysfunction, sildenafil, tadalafil, pharmacokinetics, pharmacology, drug interactions. ERECTILE DYSFUNCTION (ED), described as the inabil-ity to achieve and maintain an erection sufficient to permit satisfactory sexual intercourse, affects ap-proximately 20 to 30 million men in the United States and more than 150 million men worldwide.1,2 ED may be the result of psychological, neurological, vascular, hormonal, or cavernosal abnormalities or a combina-tion of all these factors. The traditional management of ED has included difficult to administer and often pain-ful modalities such as external vacuum devices, intracavernosal injection therapies, and intraurethral suppositories. Oral medications such as yohimbine, apomorphine, and phentolamine have also been re-ported to improve ED.3-5 However, the safety and benefi-cial effects of these oral agents have not been substantiated in clinical trials, and the Food and Drug Ad-ministration (FDA) has yet to approve any of these prod-ucts for use in the United States for the treatment of ED