Chapter 42: Antifungal Drugs

Fungal pathogens include both yeasts and molds, with Candida albicans being a common opportunistic pathogen causing oral thrush and vaginal infections in immunocompromised individuals, while more invasive organisms such as Aspergillus, Cryptococcus, Blastomyces, and Histoplasma cause life-threatening systemic disease in patients with AIDS, malignancy, or immunosuppressive therapy. The chapter details five major antifungal drug classes. Polyenes including amphotericin B and nystatin work by binding to ergosterol within fungal cell membranes, disrupting membrane integrity and causing cellular leakage leading to fungal death, with amphotericin B reserved for serious systemic infections despite significant toxicity concerns including infusion-related reactions, kidney damage, electrolyte abnormalities, and anemia. Azole antifungals encompassing both imidazoles and triazoles inhibit fungal cytochrome P-450 dependent enzymes that synthesize ergosterol, destabilizing the cell membrane and making them useful for candidiasis, aspergillosis, cryptococcosis, and prophylactic treatment in at-risk populations. Echinocandins such as caspofungin and micafungin inhibit glucan polymer synthesis necessary for fungal cell wall integrity, providing effective treatment for invasive aspergillosis and resistant Candida species. Allylamines like terbinafine block ergosterol production and are particularly effective for dermatophyte infections such as ringworm and nail infections. Adverse effects across antifungal classes include hepatotoxicity, nephrotoxicity, gastrointestinal disturbances, rashes, anemia, electrolyte imbalances, and visual abnormalities. Drug interactions are common due to cytochrome P-450 metabolism affecting anticoagulants, contraceptives, immunosuppressants, and lipid-lowering agents. Nursing responsibilities include baseline assessment of kidney and liver function, complete blood counts, electrolytes, and culture confirmation, with ongoing monitoring of infusion sites, vital signs, fluid balance, and adverse effects. Patient education addresses medication adherence over extended treatment periods, proper application of topical formulations, recognition of serious side effects, maintenance of contraception during therapy, and preventive hygiene measures.