Nystatin

Indications

Nystatin is utilized in various formulations to treat and prevent specific candidiasis infections. Orally, it addresses conditions such as oral candidiasis (thrush), intestinal candidiasis, and anal candidiasis. Topically, nystatin is effective for managing vulvovaginal candidiasis and other skin infections attributable to candida. Additionally, it is an integral component of a combination product containing neomycin, gramicidin D, and triamcinolone (Viaderm K.C.), which is prescribed for corticosteroid-responsive dermatoses of bacterial or candidal origin and conditions such as pruritus ani and pruritus vulvae. A separate combination involving metronidazole employs nystatin for treating mixed infections caused by Trichomonas vaginalis and Candida albicans. Off-label, nystatin may be administered as a secondary option to fluconazole for preventing invasive candidiasis in low birth weight neonates.

Pharmacodynamics

Nystatin functions as an antifungal agent exhibiting both fungistatic and fungicidal properties against a broad spectrum of yeasts and yeast-like fungi. Its antifungal mechanism involves the disruption of fungal cell membranes, effectively targeting Candida species. While resistance is generally minimal in Candida albicans, other Candida species may develop resistance over time. Importantly, nystatin lacks significant action against bacterial, protozoal, or viral pathogens. Due to its considerable systemic toxicity and the absence of a formulation suitable for systemic use, nystatin is presently limited to applications involving topical, oral, and gastrointestinal infections.

Absorption

When administered orally, nystatin demonstrates minimal systemic absorption. It does not achieve detectable plasma concentrations through topical or vaginal administration, ensuring that its action remains localized to the site of application.

Metabolism

Given its negligible systemic absorption, nystatin does not undergo significant metabolism. The limited nature of its absorption and metabolism underscores its suitability for non-systemic use in treating targeted fungal infections.

Mechanism of Action

Nystatin operates as a channel-forming ionophore, executing its therapeutic functions by creating pores within the plasma membrane of fungal cells. This pore formation alters the membrane's permeability, causing intracellular contents to leak out and disrupting the essential electrochemical gradients required for normal cellular activity. The specificity of nystatin for fungal cells over mammalian cells is attributed to its higher binding affinity for ergosterol, a crucial sterol present in fungal cell membranes, in contrast to cholesterol, which is found in mammalian cells.