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Overview
Compared with antibacterial agents, relatively few antimicrobials are available for treatment of fungal infections. Many substances with antifungal activity have proved to be unstable, to be toxic to humans, or to have undesirable pharmacologic characteristics, such as poor diffusion into tissues. Newer antifungal agents target fungal-specific cellular features and demonstrate lower toxicity than older drug classes.
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Many antifungals are too toxic for use
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Many fungal infections are self-limiting and require no chemotherapy. Superficial mycoses are often treated, but topical therapy can be used, thus limiting toxicity to the host. Invasive or systemic fungal infections that are not controlled by the host’s immune system require the prolonged use of antifungals. Given that most of the patients with these infections also have underlying immunosuppression, invasive mycosis can be among the most difficult of all infectious diseases to treat successfully. The characteristics of currently used antifungal agents are discussed next and summarized in Table 44–1. They are discussed in the text that follows in relation to their target of action, as illustrated in Figure 44–1.
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