Amphotericin B 1397-89-3

Amphotericin B (AmB) is a polyene antifungal discovered in the 1950s. It remains a cornerstone therapy for life-threatening invasive fungal infections (IFD) due to its unique mechanism and broad spectrum.

Mechanism of Action

Target: Fungal cell membrane ergosterol.

Process: Binds to ergosterol and creates transmembrane pores.

Result: Leakage of intracellular ions (K⁺, Na⁺, Mg²⁺) leading to rapid fungicidal (killing) activity.

Selectivity Issue: It also binds weakly to mammalian cholesterol, which explains its dose-limiting toxicity profile.

Spectrum of Activity

Amphotericin B covers nearly all clinically relevant fungal pathogens:

✅ Yeasts: Candidaspecies (high susceptibility).

✅ Cryptococci: Cryptococcus neoformans.

✅ Molds: Aspergillusspecies.

✅ Mucormycosis: Rhizopusand Mucorspecies (Critical Indication).

✅ Endemic Fungi: Histoplasma, Coccidioides, Blastomyces.

Comparative Advantages Over Other Antifungals

Compared to Azoles (e.g., Fluconazole, Voriconazole) and Echinocandins (e.g., Caspofungin):

Feature

Irreplaceable Clinical Scenarios

Amphotericin B is the definitive therapy in specific high-mortality situations:

1. Mucormycosis: The only reliable first-line treatment. Azoles and Echinocandins are ineffective.

2. Severe Azole-Resistant Candidiasis: Maintains efficacy where Fluconazole fails.

3. Empirical Therapy in Critical Illness: Provides the widest possible coverage when the pathogen is unknown.

4. Severe Hepatic Impairment: Preferred when azole hepatotoxicity is a concern.

Key Differentiators Summary

1. Best-in-class for: Mucormycosis, broad-spectrum empiric coverage, and azole-resistant infections.

2. Safety Profile: Minimal drug-drug interactions; significant renal toxicity risk with conventional formulations (mitigated by lipid formulations).

3. Unique Value: Decades of clinical use with persistently low resistance rates.