Which antifungal medication inhibits ergosterol by binding to it and forming pores rather than inhibiting ergosterol synthesis?

• A. Ketoconazole
• B. Amphotericin B
• C. Fluconazole
• D. Miconazole

Answer: (B)

Antifungals that act on the membrane do so in two main ways: by blocking ergosterol synthesis or by binding ergosterol itself to disrupt the membrane. Amphotericin B is the pore-forming one. It binds to ergosterol in the fungal cell membrane and inserts into the bilayer, creating pores. These pores let ions and other small molecules leak out, compromising the membrane and killing the cell. It doesn’t inhibit the synthesis of ergosterol; instead it uses ergosterol as a target to punch holes in the membrane.

The other drugs listed are azoles. They inhibit the enzyme 14-α-demethylase in the ergosterol biosynthesis pathway, reducing ergosterol production and weakening the membrane over time, but they do not form pores.