introduction of polyenes:

Polyenes are a class of antifungal agents that are primarily used to treat serious fungal infections. They are characterized by their large macrocyclic structures containing multiple conjugated double bonds ("polyene" chains), which is the origin of their name.

The main mechanism of action of polyenes is binding to ergosterol, a key component of fungal cell membranes. This binding disrupts the membrane's integrity, creating pores that lead to leakage of cellular contents and ultimately cell death. Due to their selectivity for ergosterol (which is absent in human cells that contain cholesterol instead), polyenes exhibit fungicidal activity with relatively low toxicity to human cells.

The most well-known polyene antifungal is Amphotericin B, often referred to as the "gold standard" for treating systemic fungal infections. Other examples include Nystatin and Natamycin, which are mainly used for topical infections.

Despite their effectiveness, polyenes can have notable side effects, particularly nephrotoxicity (especially with Amphotericin B), which has led to the development of lipid formulations to reduce toxicity.

Indications:

Indications:

Used to treat serious systemic fungal infections, including:

Systemic candidiasis

Blastomycosis

Histoplasmosis

Coccidioidomycosis

Invasive fungal infections in immunocompromised patients (e.g., HIV/AIDS, cancer)

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2. Nystatin (Mycostatin, Nilstat):

Indications:

Used for topical and mucosal fungal infections caused by Candida species, such as:

Oral thrush (oral candidiasis)

Cutaneous candidiasis (skin infections)

Vaginal candidiasis

Note: Nystatin is not absorbed systemically, so it's only used for local infections.

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3. Natamycin (Natacyn):

Indications:

Used for fungal eye infections, including:

Fungal keratitis (corneal infection)

Fungal conjunctivitis

Effective against fungi like Fusarium and Aspergillus.

Side effects:

1. Amphotericin B

Common Side Effects:

Nephrotoxicity (kidney damage) – most serious and common

Fever, chills, rigors (especially during infusion)

Hypokalemia (low potassium)

Hypomagnesemia (low magnesium)

Anemia (due to decreased erythropoietin production)

Thrombophlebitis (inflammation at IV site)

Hypotension

Note: Lipid formulations (like Ambisome) reduce nephrotoxicity and infusion-related reactions.

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2. Nystatin

Common Side Effects:

Generally well tolerated because it's not absorbed systemically

Oral form:

Nausea

Vomiting

Diarrhea

Topical form:

Skin irritation

Burning or itching sensation

Allergic reactions (rare)

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3. Natamycin

Common Side Effects (eye drops):

Eye irritation or discomfort

Blurred vision (temporary)

Redness or tearing

Allergic reactions (rare)

Precautions:

1.Amphotricin B
Precautions:

Monitor renal function closely (serum creatinine, BUN)

Regularly check electrolytes (especially potassium and magnesium)

Monitor for anemia (complete blood count)

Use with caution in patients with renal impairment or those taking other nephrotoxic drugs

Pre-medication with antipyretics, antihistamines, or corticosteroids may be needed to reduce infusion-related reactions

Contraindications:

Known hypersensitivity to Amphotericin B or any component of the formulation

Use with caution during pregnancy (Category B – considered safe if clearly needed)

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2. Nystatin

Precautions:

Topical use only – do not use systemically

Use oral form carefully in patients with gastrointestinal disorders

Avoid contact with eyes (when used as a cream or ointment)

Prolonged use may lead to fungal resistance

Contraindications:

Known allergy or hypersensitivity to nystatin or any formulation ingredients

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3. Natamycin

Precautions:

For ophthalmic use only – not for injection or systemic use

May cause temporary blurred vision, so caution is advised when driving or operating machinery

Use with care in patients with hypersensitive eyes or pre-existing ocular conditions

Remove contact lenses before application

Contraindications:

Hypersensitivity to natamycin or any component of the formulation