Week 10: lessons 28,29, 30 Antiviral drugs

Viruses are obligate intracellular parasites. They lack both a cell wall and a cell membrane, and they do not carry out metabolic processes. Viral reproduction uses much of the host’s metabolic machinery, and few drugs are selective enough to prevent viral replication without injury to the host. Therapy for viral diseases is further complicated by the fact that the clinical symptoms appear late in the course of the disease, at a time when most of the virus particles have replicated. [Note: This contrasts with bacterial diseases, in which the clinical symptoms are usually coin- cident with bacterial proliferation.] At this late, symptomatic stage of the viral infection, administration of drugs that block viral replication has lim- ited effectiveness. However, some antiviral agents are useful as prophy- lactic agents. Only a few virus groups, including those that cause the viral infections discussed in this chapter, respond to available antiviral drugs