Antifungal drug types

Definition

Many fungi live in the human body, usually without causing illness. Fungi that do cause human illness affect the skin; nails; body hair; internal organs, such as the lungs; and body systems, such as the nervous system. Antifungal medications are used to prevent the growth and reproduction of harmful fungi.

The treatment of a fungal infection depends on the type and location of infection. Superficial infections that affect the skin, hair, and nails can be treated with a topical cream or ointment. Systemic infections that affect the internal organs require aggressive treatment with either oral or intravenous drugs. Three classes of drugs typically are used to treat fungal infections: polyenes, azoles, and echinocandins.

Polyenes

Polyenes are drugs that work by attaching to the sterol component found in the fungal membrane, injuring the plasma membrane of fungi. This action causes the cells to become porous and then die. The two polyenes most commonly used are nystatin (Mycostatin) and amphotericin B (Fungizone).

Nystatin is often used as a topical agent to treat superficial infections, or it is taken orally to treat such candidal infections as oral or esophageal candidiasis. Nystatin is prescribed in oral, topical, and vaginal formulations for the treatment of fungal infections of the gastrointestinal tract, skin, and vagina, respectively.

Amphotericin B was the first antifungal drug to be approved, and it is still standard therapy for the most severe systemic fungal infections. Fungizone intravenous is specifically intended to treat potentially life-threatening fungal infections such as aspergillosis, cryptococcosis, blastomycosis, systemic candidiasis, coccidioidomycosis, histoplasmosis, and zygomycosis. This potent drug should not be used to treat noninvasive fungal infections such as oral thrush, vaginal candidiasis, and esophageal candidiasis. Several types of amphotericin B (Abelcet, Amphotec, and AmBisome) have been introduced. These drugs cause fewer side effects than traditional amphotericin B, but they are more expensive.

Azoles

Azoles stop fungal growth by preventing the production of the essential membranes that surround the fungal cell-wall. Ketoconazole (Nizoral) has been used since the 1970s. It is slightly more toxic than the other azoles and does not work for aspergillosis and many candidiasis infections.

This broad-spectrum antifungal medication is most often used to treat fungal infections that can spread to different parts of the body through the bloodstream. These infections include yeast infections of the mouth, skin, urinary tract, and certain infections that begin on the skin or in the lungs. Ketoconazole is also used to treat fungal infections of the skin or nails that cannot be treated with other medications. Topical ketoconazole is used for treating ringworm, jock itch, athlete’s foot, dandruff, and tinea versicolor (a noninflammatory infection of the skin, especially of the trunk, that is caused by a lipophilic fungus).

Fluconazole (Diflucan) is used for treating vaginal, oral, and esophageal fungal infections caused by Candida. It is effective in treating urinary tract infections, peritonitis, pneumonia, cryptococcal meningitis, and disseminated infections caused by Candida. Although fluconazole is effective against both superficial and systemic candidiasis, some strains of this fungus have now become resistant to the drug.

Itraconazole (Sporanox, Onmel, Sporanox Pulsepak) is effective against a range of fungal infections. Unlike ketoconazole or fluconazole, itraconazole can be used to treat aspergillosis. Itraconazole capsules are used to treat infections that begin in the lungs and can spread through the body; the drug is also used to treat fungal infections of the fingernails and toenails (onychomycosis). Itraconazole oral solution is used to treat yeast infections of the mouth and throat. It is active against fungal infections such as blastomycosis, histoplasmosis, and candidiasis. Because of its low toxicity profile, this agent can be used for the long-term maintenance treatment of chronic fungal infections.

Voriconazole (Vfend) is used to treat serious fungal infections such as invasive aspergillosis (a fungal infection that begins in the lungs and spreads through the bloodstream to other organs) and esophageal candidiasis (infection by a yeastlike fungus that may cause white patching in the mouth and throat). It acts as an enzyme inhibitor blocking the synthesis of ergosterol, a constituent of fungal membranes, thereby preventing the growth of the microorganism.

Clotrimazole (Lotrimin, Mycelex, Alevazol) is a broad-spectrum antifungal medication used to treat yeast infections of the vagina, mouth, and skin, including athlete’s foot, jock itch, and body ringworm. It can also be used to prevent oral thrush in certain persons. Clotrimazole is available as a cream, lotion, powder, and solution to apply to the skin; lozenges to dissolve in the mouth; and vaginal tablets and cream to be inserted into the vagina.

Sulconazole nitrate (Exelderm) is a broad-spectrum topical antifungal agent. Exelderm solution has antifungal and antiyeast activity. Sulconazole nitrate solution 1.0 percent is indicated for the treatment of jock itch, ringworm, and tinea versicolor. Effectiveness has not been proven in athlete’s foot.

Miconazole (Micatin, Zeasorb, Triple Paste AF, Miconazole-3, and Monistat) is an antifungal medication used topically to treat vaginal infections caused by C. albicans and several fungal infections of the skin, including tinea versicolor, athlete’s foot, jock itch, and ringworm. Miconazole vaginal cream and suppositories are for use only in the vagina. For fungal skin infections, the topical cream is applied as a thin layer to cover the affected skin and surrounding area. These products are not to be taken by mouth.

Echinocandins

Echinocandins make up a newer class of antifungal drugs that work by disrupting the wall that surrounds fungal cells. They are fungicidal against yeast such as Candida species and fungistatic against Aspergillus species. Their limited toxicity profile and minimal drug-to-drug interactions make them an attractive option for treating invasive fungal infections.

Four echinocandins are available on the market: caspofungin (Cancidas), micafungin (Mycamine), anidulafungin (Eraxis), and rezafungin (Rezzayo). Caspofungin is an effective treatment for severe systemic fungal infections and is given to persons who do not respond to other therapies. Micafungin is effective in treating aspergillosis in persons with leukemia. Anidulafungin is used to treat candidemia and other forms of invasive candida infections, specifically abscesses in the abdomen and peritonitis, and candida infection of the esophagus. Rezafungin is used in patients with invasive candidiasis and in those with yeast infections in the blood.

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