Amphotericin B and its Formulations

Introduction & chemistry

• Amphotericin B (AmB) is the prototype polyene macrolide antifungal and remains the gold standard for deeply invasive, life-threatening mycoses owing to its broad spectrum and fungicidal action — despite considerable toxicity. Obtained from the actinomycete Streptomyces nodosus; introduced as amphotericin B-deoxycholate in the late 1950s.
• Chemistry — an amphipathic (amphoteric) heptaene macrolide: a large lactone (macrolide) ring bearing seven conjugated trans-double bonds (heptaene) plus a mycosamine sugar (3-amino-3,6-dideoxymannose) attached by a glycosidic bond.
• Amphipathic rod — one face is lipophilic (the conjugated double bonds), the opposite face hydrophilic (many –OH groups). The amphoteric nature (hence "ampho-") arises from a –COOH on the ring and a –NH₂ on mycosamine → soluble only at extremes of pH; insoluble & unstable in water, requiring formulation for IV use.
• Less-toxic azoles and echinocandins have displaced AmB for many indications, but its broad fungicidal spectrum keeps it indispensable — increasingly used as rapid induction therapy to lower fungal burden before an azole step-down.