Systemic antifungals that are currently licensed for humans and used in animals for the treatment of invasive fungal infections (IFIs) can be grouped into four classes based on their site of action: polyenes, azoles, echinocandins, and nucleoside analogs (Fig. 16.1) (Groll et al. 1998; Dodds Ashley et al. 2006).

Figure 16.2 shows the development timeline for systemic antifungals from the 1950s to present.

A wide variety of topical agents belonging to different classes of antifungals are available as creams, ointments, gels, lotions, powders, shampoos, and other formulations. Topical antifungals can be applied to the skin, hairs, nails, or mucosa to kill or inactivate fungi. Regardless of the actual mechanism of action of the drug or the viscosity, hydrophobicity, and acidity of the formulation, the drug's ability to penetrate or permeate deeper skin layers is an important property impacting the therapeutic efficacy of topical antifungals (Durdu et al. 2017). Table 16.1 summarizes the uses of various antifungals that have proved successfully in various animal species.

16.2.1