Nystatin products are made by numerous different manufacturers.
Nystatin works by binding to ergosterol, an important component of the fungal cell membrane. This changes the fungal cell membrane, making it more "leaky" and allowing for the leakage of important cellular contents to occur.
Even when taken by mouth, nystatin is not significantly absorbed into the bloodstream (it stays in the digestive tract and is excreted through the feces). This means that it is not good for fungal infections other than those on the surface of the body (which can be treated with ointments, creams, or powders) or those of the digestive tract (which can be treated with oral forms of nystatin).