Amphotericin B deoxycholate is the gold standard antifungal for invasive aspergillosis before liposomal formulations were introduced. Its mechanism of action is:

• A Inhibition of ergosterol synthesis by blocking lanosterol 14-alpha demethylase
• B Inhibition of (1-3)-beta-D-glucan synthase, disrupting fungal cell wall
• C Binding to ergosterol in the fungal membrane, forming pores that cause potassium and other ion loss, depolarisation, and cell lysis ✓
• D Competitive inhibition of thymidylate synthase, blocking fungal DNA synthesis

Explanation

Amphotericin B is a polyene antifungal that inserts into fungal membranes by binding specifically to ergosterol (the principal fungal sterol, absent in mammalian cells which contain cholesterol). This creates transmembrane channels/pores that allow rapid efflux of K+, Na+, and other cellular ions, disrupting osmotic balance and causing cell lysis. Nephrotoxicity occurs because it has some affinity for cholesterol in renal tubular membranes. Azoles inhibit ergosterol synthesis (lanosterol demethylase); echinocandins inhibit glucan synthase; flucytosine inhibits DNA/RNA synthesis.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.