Section 18.10 Viruses use host cell metabolic machinery to replicate. However, several virus-specific enzymes and processes can be interrupted with chemotherapeutic agents to disrupt viral replication. Many clinically effective antiviral agents are nucleoside analogs, and work by inhibiting viral nucleotide polymerases, but several other agents including the protease inhibitors interfere with viral maturation steps. Host cells also produce antiviral proteins called interferons that stop viral replication. However, interferons are not yet available in clinically useful forms.
Antifungal agents fall into a wide variety of chemical categories.
As with viruses, selective toxicity is hard to achieve, but there are some effective chemotherapeutic agents. Treatment of fungal infection is now an important human health issue. An important side effect of the use of antimicrobial chemotherapeutic agents is the development of resistance by the targeted microorganisms. In many cases, resistance results from the selection of existing resistance genes. Major selection factors for resistance genes are the improper and indiscriminate uses of antimicrobial drugs.