Drugs for the treatment of impotence.

Penile erection is a complex neurovascular event that represents a balance between corporal smooth muscle relaxation and contraction. This balance is determined by the interaction between proerectile and antierectile neurotransmitters. It is believed that nitric oxide is the primary erectogenic neurotransmitter and that noradrenaline (norepinephrine) is the primary erectolytic neurotransmitter. There are a number of pharmacological approaches to the management of erectile dysfunction and manipulation of the neurotransmitter systems. These involve direct delivery of drugs into the erectile chambers (intracavernosal injection therapy), administration of medications into the urethra (transurethral delivery), application of medications to the skin (transdermal delivery) and it is hoped that oral agents will be available in the very near future. This article reviews the world literature on the medications that have been investigated to date and their delivery routes.