Anti-Fungal Drugs

Drugs targeting the cell membrane

Amphotericin B

This drug binds to ergosterols in the cell membrane to make large pores

– This leads to the leakage of cell ions causing leakage of cell content leading to cell death

– It is a broad-spectrum antibiotic which is used for many systemic fungal infections

Side effects
  • Very low therapeutic index as also affects human membranes which have cholesterol

  • Flu-like symptoms

  • Nephrotoxicity

  • Hypokalaemia

  • Hypomagnesaemia

Nystatin

This has a similar mechanism of action to amphotericin B forming pores in the membrane

– As it is so toxic, it is only used in topical treatments (e.g. for vaginal thrush)

Side effects
  • Diarrhoea

  • Rash

Azole drugs

e.g. Itraconazole + Fluconazole + Clotrimazole + Ketoconazole

These inhibit 14a-demethylase which prevents the synthesis of ergosterol in the cell membrane

– The depletion alters fluidity and permeability causing the organism to die.

Side effects
  • Inhibit liver enzymes CYP450

  • Hepatoxicity (especially Ketoconazole)

Terbinafine

This inhibits squalene epoxidase which inhibits ergosterol synthesis

– Commonly taken orally and used for superficial fungal nail infections

Side effects
  • Taste disturbance

Drugs targeting other features

Flucytosine [targets DNA]

This drug is transported into fungal cells and made into 5-fluoruracil.

– This then inhibits thymidylate synthase needed for thymine synthesis stopping fungi making DNA

Side effects
  • Vomiting

Griseofulvin [targets spindle]

Inhibits mitosis by binding to tubulin thus preventing adequate spindle formation.

– It is commonly used for dermatophyte (hair and nail) infections

Side effects
  • Induces cytochrome P450

  • Teratogenic

Capsofungin [targets the cell wall]

This prevents synthesis of the fungal cell wall causing cell death

– It is very useful in fighting candida infections

Side effects
  • Flushing of the face

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