Amphotericin B, often shortened to “Ampho,” is an effective antifungal medication that treats serious fungal infections. This drug belongs to the polyene class of antifungals and works by targeting ergosterol in fungal cell membranes, disrupting the cell’s integrity and leading to its demise. It has been a foundational treatment for invasive fungal infections for decades, active against many types of pathogenic fungi. Amphotericin B is typically reserved for severe cases where other antifungal agents may be less effective or inappropriate.
Medical Uses of Amphotericin B
Amphotericin B treats serious, often life-threatening systemic fungal infections. Its broad-spectrum activity makes it valuable against many fungal pathogens. It is used for conditions such as invasive aspergillosis, a severe lung infection, and cryptococcal meningitis, which affects the brain and spinal cord.
It also treats systemic candidiasis, an infection caused by Candida species that can affect various organs, and mucormycosis, a rare but aggressive fungal infection. It is considered for severe infections in critically ill or immunocompromised individuals. It remains effective because fungi have a low incidence of developing resistance.
Administration and Formulations
Amphotericin B is administered intravenously, typically as a slow infusion in a hospital setting, over 2 to 6 hours. This ensures the drug reaches systemic circulation effectively, as it is poorly absorbed orally. Before a full dose, a small test dose (e.g., 1 mg) may be given over 20-30 minutes to assess patient tolerance.
Distinct formulations of Amphotericin B optimize its delivery and safety. Conventional Amphotericin B deoxycholate, the older version, uses sodium deoxycholate to improve solubility. This formulation binds to ergosterol in fungal cell membranes but can also interact with cholesterol in human cells, contributing to side effects.
Newer lipid-based formulations, such as liposomal Amphotericin B (e.g., Ambisome) and Amphotericin B lipid complex (e.g., Abelcet), reduce toxicity. These formulations encapsulate the drug within lipid structures, delivering it more selectively to fungal cells and reducing exposure to human tissues, particularly the kidneys. This allows for higher doses with a lower risk of adverse effects compared to the conventional form.
Common Side Effects and Management
Amphotericin B causes infusion-related reactions, often termed “shake and bake” due to their symptoms. These reactions include fever, chills, rigors, headache, and nausea, typically appearing during or shortly after infusion. To manage these reactions, patients often receive premedications, such as acetaminophen, diphenhydramine (an antihistamine), and sometimes corticosteroids, about 30 minutes before infusion.
Beyond immediate infusion reactions, Amphotericin B carries a risk of long-term toxicities, with kidney damage (nephrotoxicity) being a primary concern. This can manifest as decreased kidney function, which may be reversible if the drug is discontinued. The drug can cause renal vasoconstriction and tubular damage, particularly with the conventional formulation.
Electrolyte imbalances are also common, specifically low potassium (hypokalemia) and low magnesium (hypomagnesemia). These imbalances can lead to muscle weakness, cramps, and irregular heart rhythms. Regular monitoring and supplementation of these electrolytes are often necessary to prevent complications during treatment.
Monitoring During Treatment
Close monitoring is standard during Amphotericin B treatment to manage potential side effects and ensure patient safety. Frequent blood tests assess kidney function, typically by measuring serum creatinine. These tests help detect kidney damage early, allowing for dose adjustments or changes in formulation.
Electrolyte levels, especially potassium and magnesium, are also tracked through blood tests due to the drug’s tendency to cause imbalances. If levels are too low, healthcare providers administer supplements to correct them. Liver function tests may also be performed, as Amphotericin B can sometimes affect the liver.
During the intravenous infusion, vital signs such as temperature, pulse, respiration, and blood pressure are regularly recorded. This helps identify acute infusion-related reactions promptly. Careful attention is also given to fluid intake and output, particularly in children, to maintain hydration and support kidney function throughout treatment.