3.15 Antifungals
Fungi are important to humans in a variety of ways. Both microscopic and macroscopic fungi have medical relevance, but some pathogenic species can cause mycoses (illnesses caused by fungi). See Figure 3.11[1] for a microscopic image of Candida albicans, which is the causative agent of yeast infections. Some pathogenic fungi are opportunistic, meaning that they mainly cause infections when the host’s immune defenses are compromised and do not normally cause illness in healthy individuals. Fungi are also major sources of antibiotics, such as penicillin from the fungus Penicillium.[2]
Mechanism of Action: Antifungals disrupt ergosterol biosynthesis of the cell membrane, increasing cellular permeability and causing cell death.
Indications: There are several classes of antifungals, each with their own indications:
Imidazoles include miconazole, ketoconazole, and clotrimazole, which are used to treat fungal skin infections such as tinea pedis (athlete’s foot), tinea cruris (jock itch), and tinea corporis (ringworm of the body).
Triazole drugs, including fluconazole, can be administered orally or intravenously for the treatment of several types of systemic yeast infections, including oral thrush and cryptococcal meningitis, both of which are prevalent in clients with AIDS. Triazoles also exhibit more selective toxicity, compared with the imidazoles, and are associated with fewer side effects.[3]
Allylamines, a structurally different class of synthetic antifungal drugs, are commonly used topically for the treatment of dermatophytic skin infections like athlete’s foot, ringworm, and jock itch. Oral treatment with terbinafine is also used for fingernail and toenail fungus, but it can be associated with the rare side effect of hepatotoxicity.[4]
Polyenes are a class of antifungal agents naturally produced by certain actinomycete soil bacteria and are structurally related to macrolides. Common examples include nystatin and amphotericin B. Nystatin is typically used as a topical treatment for yeast infections of the skin, mouth, and vagina, but may also be used for intestinal fungal infections. The drug amphotericin B is used for systemic fungal infections like aspergillosis, cryptococcal meningitis, histoplasmosis, blastomycosis, and candidiasis. Amphotericin B was the only antifungal drug available for several decades, but its use has associated serious side effects, including nephrotoxicity.[5]
Nursing Considerations: Administration guidelines will vary depending on the type of fungal infection being treated. It is important to monitor response of the affected area and examine class specific administration considerations to monitor client response.
Side Effects/Adverse Effects: Common side effects of antifungal medications can include skin irritations and rashes. Additional adverse effects include hepatotoxicity, nephrotoxicity, hypokalemia, and ototoxicity.
Health Teaching & Health Promotion: The client should be advised to follow dosage