antifungaler

Antifungaler, or antifungal agent, refers to any substance that kills or inhibits growth of fungi. They are used to treat fungal infections that can range from superficial skin conditions to invasive systemic diseases. Antifungals can be applied topically or given systemically and may be natural products, semi-synthetic derivatives, or fully synthetic compounds. Their selection depends on the organism involved, site of infection, and patient factors.

Most antifungal drugs act by targeting fungal cell membranes or cell walls, or by interfering with nucleic acid synthesis. Polyenes such as amphotericin B and nystatin bind ergosterol to disrupt membranes. Azoles (fluconazole, itraconazole, voriconazole, posaconazole) inhibit lanosterol 14-demethylase, reducing ergosterol production. Allylamines (terbinafine) block squalene epoxidase, also lowering ergosterol. Echinocandins (caspofungin, micafungin, anidulafungin) inhibit beta-1,3-glucan synthesis in the cell wall. Flucytosine disrupts fungal DNA synthesis but is rarely used alone. Resistance can arise through target modification or efflux, and cross-resistance is observed within classes.

Clinical use depends on spectrum and infection site. Azoles are common for many superficial and some systemic infections, echinocandins are preferred for certain Candida infections, and amphotericin B remains a broad-spectrum option for severe infections. Side effects vary by drug class and include nephrotoxicity (polyene), hepatotoxicity and interactions (azoles), QT effects (some azoles), and myelosuppression (flucytosine). Drug interactions are important, particularly with azoles that modulate cytochrome P450 enzymes. Monitoring and antifungal stewardship help prevent resistance and toxicity.