Nystatin is a polyene antifungal drug to which many molds and yeast infections are sensitive, including Candida. Cutaneous, vaginal, mucosal and esophageal Candida infections usually respond well to treatment with nystatin.

Like amphotericin B and natamycin, nystatin binds to ergosterol, a major component of the fungal cell membrane. When present in sufficient concentrations, it forms pores in the membrane that lead to K+ leakage and death of the fungus. Ergosterol is fairly unique to fungi, so the drug does not have such catastrophic effects on animals.

 1. Nystatin is often used as prophylaxis in patients who are at risk for fungal infections, such as AIDS
patients with a low CD4+ count and patients receiving chemotherapy.
2. It is prescribed in units, with doses varying from 100,000 (for oral infections) to 1 million (for intestinal ones). As it is not absorbed from the gut, it is safe for oral use and does not have problems of drug interactions.
3. It is also used in cellular biology as an inhibitor of the lipid raft-caveolae endocytosis pathway on mammalian cells, at concentrations around 3 µg/mL.
4. In certain cases, nystatin has been used to prevent the spread of mold on objects such as works of art. For example, it was applied to wood panel paintings damaged as a result of the Arno River Flood
of 1966 in Florence, Italy.

Nystatin is also used as a tool by scientists performing "perforated" patch-clamp electrophysiologic recordings of cells. When loaded in the recording pipette, it allows for measurement of electrical currents without washing out the intracellular contents, because it forms pores in the cell membrane that are permeable to only monovalent ions.