Antifungal drugs are used to treat and prevent fungal infections. There are several classes of antifungal drugs including polyenes, echinocandins, azoles, and others. Azole resistance can develop through mechanisms such as decreased drug concentration due to efflux pumps, target site alterations of the ERG11 gene, and bypassing of the ergosterol pathway. Amphotericin B works by binding to ergosterol in the fungal cell membrane. Ketoconazole inhibits the enzyme lanosterol 14留-demethylase. Antifungal drugs can cause side effects and are also used to treat specific fungal infections.