Describe the mechanism of action of drugs effective against viral infections. Solution Viruses are organisms that do not possess cell walls or cell membranes. Moreover many viruses are made up of envelopes which are identical to cell membranes of humans. This is why it becomes a difficult task to target a virus through other conventional drugs. Antiviral drugs generally target the genetic material of the virus i.e. DNA or RNA. These are generally nucleoside analogs which stop synthesis of DNA or RNA by getting incorporated in the growing chain. There are some antiviral drugs which induce mutation in the viral genetic machinery thus killing the virus. Some anti viral drugs can prevent entry or exit of the virus to or from an infected cell by preventing fusion of viral envelope with cell membranes of the host cell..