Anti-Fungal | Lecture | Dr. Aqsa Murtaza



ANTI-FUNGAL DRUGS


  • The disease caused by fungus is called mycoses.
  • It can cause infection either on the skin, subcutaneous or systemic.
  • The fungal cell membrane contains ergosterol. 

Drug for Subcutaneous and Systemic Mycotic Infection 

1. Amphotericin B

  • Naturally occurring polyene anti-fungal produced by Streptomyces Nodosus.
  • Drug of choice for the treatment of several life-threatening mycoses.
  • Depending on the organism and drug concentration, it is either fungicidal or fungistatic.

Mechanism Of Action

Amphotericin  B binds to the ergosterol of fungus cells. There it forms pores, which disrupts membrane function, allowing electrolytes and small molecules to leak from the cell, resulting in cell death.

Adverse Effect 

  • Fever and chills
  • Hypotension  
  • Thrombophlebitis
  • Renal insufficiency
2. Antimetabolite Antifungal

  • Flucytosine (5-FC) is a pyrimidine anti-metabolite often used with other antimetabolite agents.
  • It is fungi static.


Mechanism Of Action


5-FC enters through the fungal cell. It is converted to a series of compounds i.e. 5-fluorouracil.


Adverse Effect 

  • Reversible neutropenia
  • Thrombocytopenia
  • Dose-related bone marrow depression


3. Azole Antifungals

It is made up of 2 different classes i.e imidazole and triazole are used for the treatment 
or prophylaxis of cutaneous and systemic mycoses.

Mechanism Of Action                                

Azole are fungistatic they block the demethylation of lanosterol to ergosterol. The inhibition of ergosterol inhibits fungal cell growth.

Drug Interactions

All azole inhibits the hepatic CYTP4503A4 e.g:
  • Rifampin
  • Phenytoin

Contraindication                        

Azole are considered teratogenic.

Drug for Cutaneous Mycotic Infection

1. Squalene epoxidase inhibitors

It acts by inhibiting squalene epoxidase thereby blocking the biosynthesis of ergosterol, an essential component of fungal cell membrane.

  • Terbinafine

Oral terbinafine is a drug of choice for treating fungal infection of nails. It requires a shorter duration of therapy. 

Adverse Effect 

Diarrhea, Dyspepsia, Headache and Rash, Taste and visual disturbances have been reported.

  • Imidazole

Imidazole are azole derivative that includes:

  • Clotrimazole
  • Ketoconazole
  • Miconazole 
  • Tioconazole

The topical imidazole has a variety of uses including:
 
  • Tinea corporis
  • Tinea pedis (Athlete's foot)
  • Oropharyngeal and Vulvitis

Topical use is associated with dermatitis and edema. 



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