Which antifungal drug binds ergosterol and forms pores in fungal membranes?

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

Answer: (B)

Amphotericin B works by targeting the fungal membrane directly. It is a polyene antifungal that binds to ergosterol, a key component of the fungal cell membrane. When amphotericin B binds ergosterol, it aggregates and forms pores or channels in the membrane. These pores disrupt the membrane’s integrity, causing leakage of essential ions and small molecules, which leads to fungal cell death. This mechanism is why it’s typically fungicidal.

The other drugs listed are azoles. They don’t form pores; instead they inhibit the enzyme responsible for converting lanosterol to ergosterol, reducing ergosterol synthesis and weakening the membrane—usually yielding fungistatic effects rather than pore formation.