Amphotericin B Drug Profile

What is Amphotericin B?

Amphotericin B is a powerful antifungal medication belonging to the polyene class of antimicrobials. It is primarily used to treat serious, life-threatening fungal infections that are often resistant to other antifungal drugs. This medication is typically reserved for severe systemic fungal infections due to its potent effects and significant side effect profile.

Uses

Amphotericin B is approved for treating several serious fungal infections:

• Invasive aspergillosis: A severe lung infection caused by Aspergillus fungi, particularly dangerous in immunocompromised patients
• Cryptococcal meningitis: A brain infection often seen in patients with HIV/AIDS or other immune system disorders
• Histoplasmosis: A systemic infection caused by Histoplasma capsulatum, especially severe forms affecting multiple organs
• Candida infections: Serious bloodstream or organ infections caused by Candida species resistant to other treatments
• Mucormycosis: A rare but aggressive fungal infection that can affect the sinuses, lungs, or other organs

How it works

Amphotericin B works by binding to ergosterol, a crucial component of fungal cell membranes. This binding creates pores in the membrane, causing essential cellular contents to leak out and ultimately leading to fungal cell death. The drug is selective for fungal cells because human cells contain cholesterol instead of ergosterol in their membranes, though this selectivity is not perfect, which contributes to the medication’s side effects.

Side effects

Common side effects include:

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• Fever and chills during infusion
• Nausea and vomiting
• Headache
• Loss of appetite
• Muscle and joint pain
• Low blood pressure
• Fatigue and weakness
• Pain or irritation at injection site

Serious side effects to watch for:

• Kidney damage or failure
• Severe electrolyte imbalances (low potassium, magnesium)
• Heart rhythm abnormalities
• Severe allergic reactions
• Blood disorders including anemia

Warnings and precautions

• Kidney function monitoring: Regular kidney function tests are essential as amphotericin B can cause significant kidney damage, particularly with conventional formulations
• Electrolyte monitoring: Blood levels of potassium, magnesium, and other electrolytes must be checked frequently and supplemented as needed
• Pregnancy considerations: Classified as pregnancy category B – animal studies show no risk but human studies are limited; use only when benefits outweigh potential risks
• Pre-existing kidney disease: Patients with kidney problems require careful dose adjustment and more frequent monitoring
• Infusion reactions: Premedication with fever reducers, antihistamines, or corticosteroids may be necessary to prevent severe infusion reactions

Interactions

• Nephrotoxic drugs: Medications like aminoglycosides, cyclosporine, and vancomycin increase kidney damage risk when combined
• Digoxin: Amphotericin B-induced low potassium levels can increase digoxin toxicity and heart rhythm problems
• Corticosteroids: May worsen potassium loss, requiring more frequent electrolyte monitoring
• Diuretics: Water pills can compound electrolyte losses, particularly potassium and magnesium
• Flucytosine: This antifungal combination may increase effectiveness but also raises toxicity risk
• Zidovudine: Concurrent use may increase risk of kidney and blood-related side effects
• Pentamidine: Combination increases risk of kidney damage and low blood pressure
• Other antifungals: Some azole antifungals may reduce amphotericin B effectiveness through antagonistic effects

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Dosage

Amphotericin B dosing varies significantly based on the specific formulation used and the type of infection being treated. Conventional amphotericin B is typically dosed at 0.25-1.5 mg per kilogram of body weight daily, while lipid formulations allow for higher doses of 3-6 mg per kilogram daily due to reduced toxicity. The medication is given intravenously over several hours, usually daily or every other day. Treatment duration can range from weeks to months depending on the infection severity and patient response. All dosing must be individualized and determined by a healthcare provider based on kidney function, infection type, and patient tolerance.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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