Antiviral agents: action and clinical use.

The development of antiviral agents has been hindered by a variety of problems. There are fundamental biological differences between viruses and other infectious agents. Viruses are strictly dependent on cellular metabolic processes and possess very limited intrinsic enzyme systems and building blocks which may serve as targets for drugs. Antiviral drugs must also possess the ability to enter the host cell. Viral replication consists of a series of events, each of which can be interfered with, leading to interruption of the viral replication cycle. Currently, the major antiviral agents in therapeutic use are amantadine, idoxuridine and vidarabine. Methisazone and isoprinosine are also used in some areas. Immunoglobulins have some antiviral activity. Immune serum globulin and high titred hepatitis B immune globulin have both been used in prophylaxis of viral hepatitis. However, studies in this area have not been well controlled and results in some areas are conflicting. Interferon appears to be the most exciting antiviral agent yet discovered. However, its potential is limited by its availability, which remains dependent on biological method. Significant progress has been made recently, though, which may lead to the chemical synthesis of interferon and thus to an antiviral agent active against many viruses.