Nitric oxide synthase (NOS) is a dimeric enzyme that catalyses the production of nitric oxide (NO) in the
human body. The nitric oxide has been identified as the most interesting and vital mediators for normal and pathological
processes, including the regulation of blood pressure, neurotransmission, and macrophage defence system, but the over
production of it can be toxic, hence their inhibitors are desired. In this article, the various isoforms of NOS and their roles
are described and a detail of the development of their inhibitors has been presented. The inhibitors studied include
aminopyridines, iminopiperidines, N-phenylamidines, benzoxazolones, isothioureas, oxazepanes, thiazepanes, diazepanes,
4,5-disubstituted-1,3-oxazolidin-2-imine derivatives, thiazolidines, pyrazoles, pyrazolines, and some others.