amphotericinB

Amphotericin B is a polyene antifungal antibiotic produced by Streptomyces nodosus. It is used to treat life‑threatening systemic fungal infections and is administered intravenously due to poor oral bioavailability. Conventional amphotericin B deoxycholate is effective but associated with significant toxicity. Lipid formulations, including liposomal amphotericin B and amphotericin B lipid complex, reduce nephrotoxicity and infusion reactions and can permit higher dosing in selected cases, though they are more costly.

Mechanism of action and spectrum: amphotericin B binds to ergosterol in fungal cell membranes, forming pores that increase permeability and cause cell death. Binding to cholesterol in human cell membranes contributes to toxicity. It has broad antifungal activity against many yeasts and molds, including Candida, Cryptococcus, Aspergillus, Histoplasma, Blastomyces, Coccidioides, and some Mucorales species; activity against some species can vary, and resistance is uncommon but possible.

Pharmacokinetics and administration: the drug is given IV; oral administration is not effective. Conventional formulations are associated with notable nephrotoxicity and electrolyte disturbances. Lipid formulations distribute differently and generally have improved renal tolerability. Amphotericin B distributes widely and penetrates poorly into the central nervous system unless meningitis or meningeal inflammation is present; clearance is slow and largely dependent on renal and hepatic pathways.

Indications and monitoring: used as induction therapy for cryptococcal meningitis (often with flucytosine) and for other severe invasive fungal infections when other agents are unsuitable. Monitoring focuses on renal function, electrolytes (notably potassium and magnesium), liver enzymes, and complete blood counts. Adverse effects include fever and chills on infusion, nephrotoxicity, electrolyte abnormalities, anemia, and hepatotoxicity. Use in pregnancy is reserved for cases where benefits outweigh risks.