Pharmacotherapy in erectile dysfunction agents for self-injection programs and alternative application models.

Abstract

Previously, men with erectile dysfunction (ED) were frequently treated with penile prosthesis implants or considered to have psychogenic impotence. Since the reports by Virag and Brindley in 1932 and 1983, pharmacotherapy, by self-injection programs has become a new therapeutic concept for impotent men. In clinical practice, this application model has been generally accepted as the "golden standard" in the treatment of ED. Papaverine was first used as monotherapy, but because of side-effects such as prolonged erection, priapism, and fibrosis of the corpus cavernosum, single use of the drug was abandoned. Instead, papaverine was introduced in mixtures, e.g. together with alpha adrenoceptor-blockers as phentolamine, and/or prostaglandin E1 (PGE1) in these "cocktails", the dose of papaverine is reduced to 10-15 mg compared to the high doses (80-120 mg) that were used initially. By having two or more drugs in the mixture, a facilitating cascade effect as probably obtained. PGE1 is the only drug that has been approved by the FDA and is today registered in more than 50 countries. Other combination therapies such as vasoactive intestinal polypeptide+ phentolamine, or calcitonin gene-related peptide+ PGE1, have been suggested as suitable alternatives for intracavernosal injection. Transdermal and intraurethral application models may be considered in selected patients. Recently, oral administration of a phosphodiesterase inhibitor (UK-92.480) was reported to improve penile erection in patients with psychogenic impotence. Further clinical results from controlled trials will probably explain if this new oral drug will compete with PGE1 or other agents in self-injection programs.