Neural and pharmacological determinants of erection

An integrative analysis of the determinants of erection will reveal that almost all the common actions of smooth muscle and endothelial cells found in normal vascular biology (NVB), and some neural mechanisms, have roles in supporting erectile function. Many of these cellular mechanisms have been harnessed to create drugs that are or will be used to treat erectile dysfunction. Without standard diagnostic or therapeutic methods, or classifications, it is difficult to compare drugs, and difficult to target the specific deficiencies causing erectile dysfunction. A classification is suggested here that hinges on the identification of two main characteristics. Firstly, there is a fundamental difference between initiating an erection (initiators) and facilitating or enhancing an erection already initiated by other processes (conditioners), and secondly, there are different implications for adverse effects and drug delivery that arise from targeting central nervous system or peripheral systemic processes. These properties suggest a classification of treatments based on a two-by-two matrix. Within each class drugs will be more equivalent enabling better comparisons and more standardized evaluative strategies. By observing the characteristics of patients benefiting from drugs of an identified class it may be possible to develop a physiologically based classification of diagnoses. There may be logical combinations of drugs that will be assembled in clinical practice, taking suitable agents from one of two or more classes. No single mechanism will stand out as overwhelming and no single drug will treat all erectile dysfunction.