Fungal infections range from mild skin infections to serious systemic diseases, especially in patients with weak immunity. Antifungal antibiotics are medicines used to treat these infections. They act by damaging fungal cell membranes, blocking cell wall synthesis, or interfering with fungal metabolism. Unlike bacteria, fungi are eukaryotic organisms, so antifungal drugs need to be more selective to avoid harming human cells.
Classification of Antifungal Antibiotics
Antifungal agents are broadly classified into:
- Polyenes
- Azoles
- Echinocandins
- Allylamines
- Other antifungal agents
POLYENES
Polyenes are powerful antifungal antibiotics that act by binding to ergosterol, a key lipid in fungal cell membranes. This creates pores, leading to leakage of cell contents and fungal death.
1. Amphotericin B
Known as the “ampho-terrible” because of its toxicity but remains the drug of choice for many life-threatening fungal infections.
Uses
- Systemic fungal infections such as cryptococcosis, histoplasmosis, mucormycosis, and aspergillosis
- Visceral leishmaniasis
Adverse Effects
- Fever, chills
- Kidney damage (major concern)
- Low potassium and magnesium levels
- Inflammation at injection site
2. Nystatin
Nystatin is used only for local fungal infections because it is not absorbed from the skin or gut.
Uses
- Oral candidiasis (thrush)
- Vaginal candidiasis
- Skin fungal infections
AZOLES
Azoles inhibit fungal sterol synthesis by blocking the enzyme required to make ergosterol. They are divided into:
- Imidazoles: ketoconazole, miconazole, clotrimazole
- Triazoles: fluconazole, itraconazole, voriconazole, posaconazole
Uses
- Superficial infections (clotrimazole, miconazole)
- Systemic infections (fluconazole, itraconazole)
- Cryptococcal meningitis (fluconazole)
- Aspergillosis (voriconazole)
Side Effects
- Nausea, vomiting
- Liver toxicity
- Hormonal disturbances (ketoconazole)
- Drug interactions due to CYP450 inhibition
ECHINOCANDINS
Echinocandins inhibit beta-glucan synthesis in fungal cell walls, making them highly effective against Candida and Aspergillus.
Common Drugs
- Caspofungin
- Micafungin
- Anidulafungin
Uses
- Invasive candidiasis
- Aspergillosis (when other drugs fail)
Side Effects
- Fever
- Rash
- Mild liver enzyme elevation
ALLYLAMINES
Allylamines block squalene epoxidase, an enzyme needed for ergosterol synthesis.
Common Drugs
- Terbinafine
Uses
- Fungal nail infections
- Skin infections like ringworm
Side Effects
- GI upset
- Liver problems
OTHER ANTIFUNGAL AGENTS
1. Flucytosine
Converted into 5-FU inside fungal cells, inhibiting DNA synthesis.
- Mainly used with amphotericin B
2. Griseofulvin
Used for skin, hair, and nail infections caused by dermatophytes.
3. Tolnaftate
Used topically for ringworm and athlete’s foot.
Superficial vs Systemic Fungal Infections
- Superficial infections: treated with topical drugs like clotrimazole, miconazole, nystatin
- Systemic infections: treated with amphotericin B, fluconazole, itraconazole, echinocandins
Detailed Notes:
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