Amphotericin B

Serious Fungal Infections

Amphotericin B is used to treat severe, progressive, and potentially fatal fungal infections. Because of its potency, it is typically reserved for systemic infections rather than minor or superficial ones. Healthcare providers often use it when other antifungal medications have not worked or are not appropriate for the patient's condition.

Conditions Treated

This medication is effective against a variety of serious fungal conditions, including:

• Aspergillosis: An infection that often affects the lungs.
• Blastomycosis: A fungal infection that can affect the lungs, skin, and bones.
• Candidiasis: Severe, widespread yeast infections that affect the blood or internal organs.
• Coccidioidomycosis: Also known as Valley Fever.
• Cryptococcosis: An infection that can lead to fungal meningitis.
• Histoplasmosis: A lung infection caused by inhaling spores.
• Mucormycosis: A rare but very serious fungal infection.
• Sporotrichosis: A fungal infection that can affect the skin and other parts of the body.

Other Uses

In some cases, amphotericin B is used to treat leishmaniasis, a disease caused by parasites transmitted through the bite of certain sandflies. It is not used to treat minor fungal infections, such as oral thrush or vaginal yeast infections, in individuals with normal immune systems.

Mechanism of Action

Amphotericin B belongs to a class of medications known as antifungals. It works by targeting the cell membrane, which is the protective outer layer of a fungal cell.

The medication attaches itself to a specific component called ergosterol, which is found in the fungal cell membrane. Once attached, amphotericin B creates tiny holes or pores in the membrane. These holes cause the following to happen:

• Leakage: Essential components inside the fungal cell leak out through the newly formed pores.
• Disruption: The loss of these internal materials prevents the fungus from functioning properly.
• Cell Death: Depending on the amount of medication used and the type of fungus, the cell either stops growing or dies completely.

By breaking down the integrity of the fungal cell, amphotericin B helps the body control and eliminate serious fungal infections.

Common Side Effects

Many people experience side effects during or shortly after receiving an infusion of amphotericin B. These common symptoms may include:

• Fever and chills
• Nausea and vomiting
• Loss of appetite or weight loss
• Headache
• Diarrhea or stomach pain
• Muscle or joint pain
• Dizziness or flushing

Serious Side Effects

Some side effects can be severe and require immediate medical attention. Contact a healthcare provider right away if you experience:

• Signs of kidney problems, such as decreased urination or swelling in the feet and ankles
• Irregular heartbeat or chest pain
• Shortness of breath or difficulty breathing
• Signs of low potassium, such as muscle weakness or cramping
• Yellowing of the skin or eyes (jaundice)
• Seizures or unusual tiredness
• Blurred vision or hearing loss
• Skin rash, hives, or itching

Boxed Warning

Amphotericin B should only be used to treat progressive and potentially fatal fungal infections. It is not intended for use in treating common, non-invasive fungal infections, such as those affecting the mouth, throat, or vagina, in patients with normal white blood cell counts.

Kidney Toxicity

Kidney damage is a significant risk associated with this medication. Healthcare providers monitor kidney function tests, such as blood urea nitrogen (BUN) and serum creatinine, frequently during treatment. If kidney function declines significantly, the dosage may need to be adjusted or the medication stopped temporarily. Staying well-hydrated may help reduce the risk of kidney issues.

Infusion-Related Reactions

Acute reactions often occur during or shortly after the intravenous infusion. These symptoms may include:

• Fever and chills
• Nausea and vomiting
• Headache
• Low blood pressure
• Muscle or joint pain
• Shortness of breath

Medical teams may provide other medications before the infusion, such as antihistamines or corticosteroids, to help reduce the severity of these symptoms.

Electrolyte and Blood Monitoring

Treatment can lead to low levels of potassium and magnesium in the blood. Regular blood tests are necessary to monitor these electrolytes, as well as liver function and complete blood counts. Anemia is a common side effect during prolonged therapy and may require monitoring of red blood cell levels.

General Precautions

This medication is contraindicated in individuals with a known hypersensitivity to amphotericin B unless the condition being treated is life-threatening and no other options are available. Caution is required when using this drug alongside other medications that can also damage the kidneys, such as certain antibiotics or chemotherapy agents.

Pregnancy

There are no adequate and well-controlled studies of amphotericin B in pregnant women. Research in animals using doses similar to human doses has not shown evidence of harm to the developing fetus. However, because animal studies do not always predict how a human will respond, healthcare providers generally reserve this medication for use during pregnancy only when it is clearly needed to treat a serious or life-threatening infection.

Breastfeeding

It is not known whether amphotericin B is excreted in human breast milk. Because many medications can pass into milk and there is a potential for serious adverse reactions in nursing infants, a decision must be made whether to stop breastfeeding or stop the medication. This decision is based on the importance of the drug to the mother's health. Patients should discuss the risks and benefits with their healthcare team to determine the safest course of action.

Available Forms

Amphotericin B is available as an injection for intravenous infusion. It is produced in several distinct formulations, which are not interchangeable. These include:

• Conventional Amphotericin B: This form is supplied as a sterile powder for reconstitution.
• Liposomal Amphotericin B: This formulation encapsulates the medication within small fat-like particles.
• Amphotericin B Lipid Complex: This version combines the medication with specific lipid molecules.
• Amphotericin B Cholesteryl Sulfate Complex: This is another lipid-based formulation designed for intravenous use.

Because these products have different safety and efficacy profiles, they cannot be substituted for one another without specific medical guidance.

FDA Approval and Indications

Amphotericin B is approved by the U.S. Food and Drug Administration (FDA) for the treatment of progressive and potentially fatal systemic fungal infections. It is a potent medication typically used when other antifungal treatments are not effective or appropriate. Approved indications include the treatment of:

• Aspergillosis
• Blastomycosis
• Disseminated candidiasis
• Coccidioidomycosis
• Cryptococcosis
• Histoplasmosis
• Mucormycosis

Specific lipid-based formulations are also FDA-approved for the treatment of visceral leishmaniasis and for managing suspected fungal infections in patients with fever and low white blood cell counts (febrile neutropenia).

Boxed Warning

The FDA has issued a boxed warning for amphotericin B. This warning specifies that the drug should be used primarily for the treatment of patients with progressive and potentially fatal fungal infections. It is not intended for use in treating non-invasive fungal diseases, such as oral thrush, vaginal yeast infections, or esophageal candidiasis in patients with normal white blood cell counts.

Regulatory Requirements for Administration

Due to the risk of serious side effects, including kidney toxicity and severe infusion reactions, the FDA requires that amphotericin B be administered under close medical supervision, typically in a hospital setting. Healthcare providers must perform regular laboratory testing to monitor kidney function, liver function, and electrolyte levels throughout the course of treatment. Different formulations of amphotericin B (conventional versus lipid-based) have different dosage requirements and are not interchangeable.

Treatment of Serious Infections

Amphotericin B is primarily reserved for severe systemic fungal infections. It is not typically used for minor fungal infections, such as those affecting only the skin, mouth, or vagina.

Types of Fungal Infections

This medication is used to treat a variety of serious infections, including:

• Aspergillosis: An infection that often affects the lungs.
• Blastomycosis: A fungal infection that can affect the lungs, skin, and bones.
• Candidiasis: Severe, widespread yeast infections.
• Coccidioidomycosis: Also known as Valley Fever.
• Cryptococcosis: An infection that can lead to meningitis.
• Histoplasmosis: A lung infection caused by inhaling fungal spores.
• Mucormycosis: A rare but very serious fungal infection.

Because these infections can be life-threatening, amphotericin B is often a critical part of the treatment plan when other antifungal medications may not be effective or appropriate. It is usually administered by a healthcare professional in a hospital setting to ensure the patient is monitored closely during the infusion.