Mechanism of Action and Pharmacokinetics
Nystatin is a natural antibiotic, specifically a polyene antibiotic. Its main pharmacokinetic feature upon oral administration is the near-total absence of absorption. The active substance passes through the gastrointestinal tract (GI) in transit and is excreted unchanged in the feces.
This exact property (excretion of unabsorbed substances via the intestine) makes the drug an excellent tool for local therapy within the intestinal lumen. It achieves decontamination without entering the systemic circulation, avoiding systemic adverse effects.
Spectrum of Activity and Classification
The drug has a narrow, but clinically crucial spectrum of activity. It is most effective against yeast-like fungi of the genus Candida (the most common pathogen being Candida albicans).
In the classification of polyene antibiotics, there are several key representatives that differ in their clinical application:
- Amphotericin B — the main drug for treating severe systemic mycoses.
- Nystatin and Levorin — drugs for topical application and GI decontamination.
- Natamycin.
Unlike amphotericin B, nystatin is not used systemically. This is due to its high toxicity when introduced into the bloodstream and its pharmacokinetic profile. While pharmacologists create complex lipid formulations to reduce the nephrotoxicity of amphotericin B (liposomal AmBisome, lipid complex Abelcet, colloidal dispersion Amphocil), the safety strategy of nystatin relies exclusively on its local and enteral administration.
Indications: Treatment and Prevention of Candidiasis
The primary indication for use is candidiasis. These fungal infections can present superficially, affecting the oral cavity, intestines, and urogenital tract.
Special attention in clinical pharmacology is given to the prophylactic use of Nistatinum. Dysbiosis (disruption of the normal balance of mucosal microflora) is a specific adverse effect of antimicrobial pharmacotherapy.
The pathogenesis of fungal superinfection develops as follows:
- Broad-spectrum antibiotics cause the death of beneficial competitive microflora.
- Local mucosal immunity decreases.
- Opportunistic flora, particularly Candida fungi, actively proliferate.
To prevent this complication, the strategy of rational drug combination is applied. The combination of "Broad-spectrum antibiotics + Nystatin (or Levorin)" is considered therapeutically appropriate. In this case, the antifungal drug acts as etiotropic therapy, mitigating the adverse reactions of the antibiotic (prevention of candidiasis).
Formulations and Administration
To ensure local action in various sites, the drug is available in multiple dosage forms. Dosing is performed not in grams, but in IU (International Units):
- Tablets: 250,000 and 500,000 IU. Administered orally for GI decontamination.
- Suppositories (rectal and vaginal): 250,000 and 500,000 IU. Used rectally (for lower intestinal candidiasis) and intravaginally (for urogenital candidiasis).
- Ointment: available in 15 and 30 g tubes. Active substance concentration: 1 g of ointment contains 100,000 IU. Applied topically for skin and mucosal lesions.