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Polyenes


  • Bind to ergosterol in the fungal cell membrane → formation of pores in the fungal membrane → disruption of electrolyte balance → cell lysis → cell death
    • It binds cholesterol to a degree, which explains a large number of its adverse effects.

Amphotericin B

Adverse effects

  • Nephrotoxicity: Lipid-based formulations of the drug and IV hydration reduce nephrotoxicity.
  • IV phlebitis
  • Impaired renal tubule permeability → hypokalemia and hypomagnesemia (restoring K+ and Mg2+ while administering the drug can counter this effect)
  • Fever, chills (amphotericin B is sometimes referred to as “shake and bake”)
  • Bone marrow suppression, anemia
  • Arrhythmias

Nystatin

Azoles


  • Mechanism of action
    • Inhibition of 14-alpha demethylase, a fungal cytochrome P450 → ↓ fungal synthesis of ergosterol from lanosterol → ↓ levels of ergosterol → membrane instability → cellular death.

Echinocandins


  • Drugs
    • Caspofungin
    • Anidulafungin
    • Micafungin
  • Route of administration: IV
    • Mechanism of action: inhibition of β-glucan synthesis → disruption of fungal cell wall synthesis → ↓ resistance against osmotic forces → cell death
  • Clinical use
  • Adverse effects
    • Flushing (due to release of histamine)
    • Hepatotoxicity
    • Gastrointestinal upset

Benzofurans (griseofulvin)


  • Route of administration: oral
  • Mechanism of action: griseofulvin binds to keratin precursor cells → accumulation in keratin-rich tissues (e.g., nails, hair) → entry into the fungal cell → interference with microtubule function → disruption of fungal mitosis
  • Clinical use: dermatophyte infections (e.g., tinea pedis)

Antimetabolites (flucytosine)


  • Route of administration: oral
  • Mechanism of action: converted to 5-fluorouracil by fungal cytosine deaminase, thereby inhibiting DNA and RNA synthesis