Antifungals

Antifungals are a broad group of medications used to treat fungal infections that affect the skin, nails, mouth, lungs, blood, and other parts of the body. Fungal infections are caused by organisms such as yeast and molds, including Candida and Aspergillus. These infections range from mild and superficial to severe and life-threatening, especially in people with weakened immune systems.

Antifungal medications are designed to kill fungi or stop them from growing. Fungi have unique cell structures that are different from bacteria and human cells, which allows antifungal drugs to target them specifically.

Fungal infections, also called mycoses, can involve the skin, nails, mouth, throat, lungs, bloodstream, or internal organs. Common examples include yeast infections, thrush and esophageal candidiasis, tinea infections such as athlete’s foot, and more serious infections like invasive aspergillosis or fungal meningitis.

Antifungal medicines are used to treat both localized fungal skin infections and systemic fungal infections that spread throughout the body.

Antifungals work by targeting structures or processes that are essential to fungal survival. The mechanism of action varies by drug class, but most antifungal drugs interfere with the fungal cell membrane or fungal cell wall.

Many antifungals target ergosterol, a key component of the fungal cell membrane. Without enough ergosterol, the fungal cell membrane becomes weak and leaky, causing the fungus to die. Other antifungals are inhibitors of enzymes involved in making ergosterol or disrupt fungal cell wall production by inhibiting glucan synthase.

Some antifungals are fungicidal, meaning they kill fungi directly, while others are fungistatic and stop fungi from growing, so the immune system can clear the infection. These effects explain how antifungal therapy can be tailored to different infections and levels of severity.

There are several major classes of antifungal drugs. Each class targets fungi differently and is used for specific infections.

Azoles

Azole antifungals are one of the most commonly used classes of antifungal medicines. They block enzymes involved in ergosterol production and interfere with cytochrome P450 pathways.

Imidazoles (often topical):

Clotrimazole (Canesten, Lotrimin, FungiCURE).

Miconazole (Daktarin, Zeasorb).

Ketoconazole (Nizoral).

Triazole antifungals (often oral or IV):

Fluconazole (Diflucan).

Itraconazole (Sporanox, Tolsura).

Voriconazole (Vfend).

Posaconazole (Posanol, Noxafil PowderMix).

Isavuconazole (Cresemba).

Polyenes

Polyenes bind directly to ergosterol in the fungal cell membrane, causing cell death.

Amphotericin B (AmBisome, Abelcet, Amphotec, Fungizone).

Nystatin (Mycostatin, Nystop, Nilstat).

Echinocandins

Echinocandins inhibit glucan synthase, which weakens the fungal cell wall.

Caspofungin (Cancidas).

Micafungin (Mycamine).

Anidulafungin (Eraxis).

Allylamines

Allylamines block squalene metabolism, disrupting ergosterol formation.

Terbinafine (Lamisil).

Other antifungal agents

Flucytosine (Ancobon).

Antifungals are used to treat a wide range of fungal infections, from mild skin conditions to life-threatening diseases.

Superficial/cutaneous infections: Antifungal treatment is commonly used for fungal skin infections such as tinea, athlete’s foot, ringworm, and fungal dermatitis. These infections often respond well to topical antifungal drugs in creams, ointments, or gels.

Yeast infections and candidiasis: Antifungal medicines treat yeast infections affecting the vagina, mouth, throat, and esophagus. Thrush and candidiasis are commonly caused by Candida species and are often treated with azoles or nystatin.

Onychomycosis, a fungal infection of the nails, often requires oral antifungal therapy such as terbinafine or itraconazole.

Systemic fungal infections affect internal organs and the bloodstream. These include invasive aspergillosis, disseminated candidiasis, and fungal meningitis. Treatment often requires intravenous antifungal agents such as amphotericin B or echinocandins.

Prevention and high-risk patients: In people with weakened immune systems, antifungal therapy may be used to prevent fungal infections. This includes patients with cancer, organ transplants, or other conditions that increase infection risk.

Antifungals can cause side effects, which vary depending on the drug, dose, and route of administration.

Common side effects include:

• Nausea or gastrointestinal upset.

• Headache.

• Skin rash or itching.

More serious side effects can occur with certain antifungal drugs. Hepatotoxicity is a known risk with some azole antifungals and requires liver function monitoring. Amphotericin B is associated with nephrotoxicity and renal complications. Allergic reactions, infusion-related reactions, and electrolyte imbalances may also occur.

These are not all of the possible side effects of antifungals. You should always seek medical advice from your healthcare provider for any questions or concerns about your medical condition or treatment. Read all patient information, medication guides, or drug information sheets that come with this medication. You can also report adverse effects to the Food and Drug Administration at www.fda.gov/medwatch or 1-800-FDA-1088.

Although these medications are generally well-tolerated and safe, there are certain warnings, precautions, and drug interactions you should be aware of.

Warnings

Before starting antifungals, it is crucial to discuss any existing health conditions with your healthcare provider. You should be sure that your healthcare provider is aware of all your medical conditions, including:

• Liver disease or elevated liver enzymes.

• Kidney or renal disease.

• A history of allergic reactions to antifungal agents.

Some antifungal drugs require close monitoring due to potential toxicity.

Boxed Warning

Some formulations of amphotericin B carry warnings related to severe toxicity, including kidney damage and infusion reactions. These medications are typically reserved for serious infections and used in hospital settings.

Contraindications

Certain antifungal drugs may not be appropriate for people with severe liver disease, kidney disease, or known hypersensitivity. Your healthcare provider will determine if a specific antifungal drug is safe for you.

Drug interactions

Antifungals, especially azoles, can interact with many other medications due to effects on cytochrome P450 enzymes. When antifungals are taken with other prescription drugs, supplements, or over-the-counter products, drug interactions may occur.

Certain heart and cholesterol medications, including statins and blood thinners, immunosuppressants, HIV medications, and benzodiazepines, may have reduced effects when combined with azole antifungals.

Enzyme inducers such as phenytoin and acid blockers (PPIs, antacids) may reduce levels of azole antifungals.