Not used in erectile dysfunction ?
Phenylephrine Human penis is made up of two spongy structures i.e., - Corpora cavernosa - Corpora spongiosum These structures contain distensile channels that become filled with blood when the aerial circulation is increased. The enlargement of the aerial channels presses on the veins situated in these structures preventing outflow of blood through them. The collection of blood in the distensile channels due to aerial dilatation leads to penile erection. Erection is mediated by parasympathetic nerves (S2, S3, S4) and non adrenergic and noncholinergic pathways which induces release of NO from endothelium in penile vasculature. NO induces vascular smooth muscle relaxation allowing enhancement of blood flow leading to erection. The primary drugs used in erectile dysfunction e.g. Slidenafil, Tadalafil and Vardenfil act on Nitric oxide pathway to improve erectile dysfunction. Nitric oxide mediates its action by increasing cGMP concentration. cGMP is finally degraded by an enzyme phosphodiesterase type 5 (PDE-5). Slidenafil and other oral agents are inhibitors of phosphodiesterase enzyme (PDE-5). These enzymes inhibits PDE-5 and thus they reduce the degradation of cGMP. Increased cGMP facilitates the relaxation of distensile channels of penis. Besides phosphodiesterase inhibitors several other drugs are also used these days - Prostaglandin Ei. E2 - Alprostadil - Transurethral alprostadil - Injectable phentolamine - Apomorphine (used in Europe only) PQK - Intracavernous injection PGE1 is widely used for treating erectile dysfunction. - PGE2 (intrauretbrall) can also be used to increase penile blood flow and treat erectile dysfunction. It relaxes human corpus cavernosum. Phenvlephrine - It is dung of choice for priapism
PGE-2
Vardenifil
Phenylephrine
Alprostadil