Generic Name

Nystatin

Mechanism

The Nystatin fungicidal activity is primarily mediated through membrane disruption:
• Ergosterol binding – Nystatin has a high affinity for the ergosterol component of fungal plasma membranes.
• Pore formation – Binding induces the creation of trans‑membrane ion channels.
• Ion leakage – Potassium, sodium, and chloride ions escape, disturbing osmotic balance and leading to cell death.
• Selective toxicity – Human cell membranes lack ergosterol; thus, systemic toxicity is minimal.

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Pharmacokinetics

• Absorption – Virtually unchanged and very poorly absorbed from the GI tract; systemic exposure is <1 % of the administered dose.
• Distribution – Primarily confined to the lumen of the GI tract or the superficial tissues where applied.
• Metabolism – No significant hepatic metabolism.
• Excretion – Primarily unaltered, excreted in feces (oral suspension) or via local elimination (topical).
• Special populations
• Children and infants: dosing frequency may be increased but systemic exposure remains negligible.
• Malabsorptive patients (e.g., cystic fibrosis): high‑dose oral suspension is used to keep the drug within the gut lumen.

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Indications

• Oral cavity candidiasis (thrush) – oral suspension or lozenges.
• Esophageal candidiasis – topical oral rinse or slurry.
• Cutaneous candidiasis – 1 % cream, ointment, powder, or wash.
• Vaginal candidiasis – 4 mg suppository or gel.
• Diaper dermatitis – cream or wash.
• Intestinal candidiasis in malabsorptive states – high‑dose oral suspension.

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Contraindications

• Hypersensitivity to nystatin or other polyene antifungals.
• None for topical use in pregnancy and lactation; safe when applied externally.
• Rare systemic toxicity (neutropenia, eosinophilia, interstitial nephritis) – mainly associated with prolonged high‑dose therapy.
• Caution with patients who develop oral mucosal irritation or urticaria during therapy; discontinue if severe reaction ensues.
• Do not use for invasive Candida disease (e.g., bloodstream infection, meningitis).

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Dosing

Administration tips
• For oral suspension, use the *spit technique*: swish for 30–60 s, spit it out; avoid swallowing large volumes to minimize GI upset.
• For infants, give a thin layer of cream to the diaper area and apply gently to the skin.
• Do not triturate capsules for children; use the suspension or liquid preparates.

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Adverse Effects

Common
• Oral irritation, taste changes (bitter or metallic).
• Mild diarrhea or abdominal discomfort (due to high‑dose oral suspension).
• Contact dermatitis around application site.

Serious (rare)
• Allergic reactions (urticaria, angioedema).
• Hypersensitivity pneumonitis.
• Neutropenia or eosinophilic granulocytosis (very uncommon).

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Monitoring

• Clinical response – resolution of lesions or oral symptoms within 4–7 days.
• CBC – only if prolonged high‑dose therapy (>2 weeks) or systemic exposure suspected.
• Signs of hypersensitivity – monitor for rash, itching, wheezing.
• Kidney function – baseline serum creatinine if using for GI candidiasis in patients with renal impairment (due to rare nephrotoxicity).

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Clinical Pearls

• First‑line for superficial candidiasis: Nystatin’s topical potency and minimal systemic absorption make it the gold standard for oral, cutaneous, and vaginal yeast infections.
• “Spit technique” is crucial: Spit to prevent GI upset and hold the drug in contact with mucosal surfaces for maximum efficacy.
• High‑dose oral suspension (>500 IU/mL) keeps drug in the gut lumen: Use in malabsorptive patients like cystic fibrosis or short‑bowel syndrome to treat intestinal candidiasis.
• Not for invasive disease: Nystatin’s poor absorption and limited activity against bloodstream infection render it ineffective for invasive candidiasis; azole or amphotericin B must be used instead.
• Avoid combination with systemic azoles when treating GI candidiasis – co‑administration may reduce GI luminal concentrations due to increased absorption but has not been shown to be necessary.
• Prophylaxis in CF infants: 5 × daily 200,000 IU oral suspension is an evidence‑based strategy to prevent breakthrough intestinal candidiasis and associated morbidity.
• Packaging matters: Prepare the suspension fresh (500 IU/mL) from a lyophilized ampoule or use pre‑filled O.C. for consistent dosing.
• Remember the “sticky‑cream” problem: The 1 % cream is sticky; a thin layer on the skin mitigates the itchiness and reduces the risk of transfer to clothing.

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