Diflucan (fluconazole) is an antifungal medicine.It belongs to a class of drugs called azole antifungals. It works by stopping the growth of certain types of fungus.Diflucan is used to treat infections caused by fungus, which can invade any part of the body including the mouth, throat, esophagus, lungs, bladder, genital area, and the blood.Diflucan is also used to prevent fungal infection in people with weak immune systems caused by cancer treatment, bone marrow transplan