Viruses present a more difficult problem of chemotherapy than do higher organisms, . bacteria, for they are intracellular parasites that use the metabolism of host cells. Highly selective toxicity is, therefore, harder to achieve. Identification of differences between viral and human metabolism has led to the development of effective antiviral agents, whose roles are increasingly well defined. Fungus infections range from inconvenient skin conditions to lifethreatening systemic diseases; the latter have become more frequent as opportunistic infections in patients immunocompromised by drugs or AIDS, or receiving intensive medical and surgical interventions in ICUs. . | 14-------------------- Viral fungal protozoal and helminthic infections SECTION SYNOPSIS Viruses present a more difficult problem of chemotherapy than do higher organisms . bacteria for they are intracellular parasites that use the metabolism of host cells. Highly selective toxicity is therefore harder to achieve. Identification of differences between viral and human metabolism has led to the development of effective antiviral agents whose roles are increasingly well defined. Fungus infections range from inconvenient skin conditions to lifethreatening systemic diseases the latter have become more frequent as opportunistic infections in patients immunocompromised by drugs or AIDS or receiving intensive medical and surgical interventions in ICUs. Protozoal infections. Malaria is the major transmissible parasitic disease in the world. The life cycle of the plasmodium that is relevant to prophylaxis and therapy is described. Drug resistance is an increasing problem and differs with geographical location and species of plasmodium. Helminthic infestations cause considerable drugs that are effective against these organisms are summarised. Viral infections Antiviral agents are most active when viruses are replicating. The earlier that treatment is given therefore the better the result. An important difficulty is that a substantial amount of viral multiplication has often taken place before symptoms occur. Apart from primary infection viral illness is often the consequence of reactivation of latent virus in the body. In both cases patients whose immune systems are compromised may suffer particularly severe illness. Viruses are capable of developing resistance to antimicrobial drugs with similar implications for the individual patient for the community and for drug development. An overview of drugs that have proved effective against virus diseases appears in Table . Herpes simplex and varicella-zoster ACICLOVIR Aciclovir inhibits viral DNA synthesis .
