- Chemical Name: Amphotericin B
- Molecular Formula: C₄₇H₇₃NO₁₇
- Molecular Weight: 924.09 g/mol
- Structure: Macrolide polyene antibiotic with a large lactone ring (38-membered) and multiple conjugated double bonds
- Solubility: Poorly soluble in water, soluble in dimethyl sulfoxide (DMSO) and dimethylformamide (DMF)
- Stability: Degrades in light, heat, and extreme pH; stored as a lyophilized powder
- Mechanism of Action: Primary Action: Binds to ergosterol (a key fungal membrane sterol), forming pores → disrupts membrane integrity → leakage of ions and cell death
- Secondary Effects:
- Induces oxidative damage via reactive oxygen species (ROS)
- Stimulates immune responses (cytokine release)
- Spectrum of Activity: Fungi (Broad-spectrum against most pathogenic fungi)
- Candida spp. (including C. albicans, C. glabrata)
- Aspergillus spp.
- Cryptococcus neoformans
- Histoplasma capsulatum
- Blastomyces dermatitidis
- Mucorales (e.g., Rhizopus, Mucor)
- Resistance: Rare but can occur via ergosterol depletion or altered membrane composition
- Administration: IV (poor oral bioavailability)
- Distribution: Highly protein-bound (>90%), penetrates tissues (lung, liver, spleen) but poorly into CSF (~2-4% of serum levels)
- Metabolism: Minimal hepatic metabolism
- Excretion: Slow renal and biliary elimination (half-life ~15 days)
- Dosing: Typically 0.5–1.5 mg/kg/day (varies by formulation and indication)
- Formulations:
- Conventional Amphotericin B (AmB deoxycholate)
- Higher toxicity (nephrotoxicity, infusion reactions)
- Cheaper, widely available
- Lipid Formulations (reduced toxicity):
- Liposomal (L-AmB, e.g., AmBisome®) – Lower nephrotoxicity
- Lipid Complex (ABLC, e.g., Abelcet®) – Larger lipid-drug particles
- Colloidal Dispersion (ABCD, e.g., Amphotec®) – Less commonly used
- Conventional Amphotericin B (AmB deoxycholate)
