Vidarabine, or araA, is used topically for ocular herpesvirus and systemically for herpetic encephalitis and neonatal herpesviral infections. This drug is an adenosine derivative that is phosphorylated by cellular enzymes to a triphosphate compound that inhibits many viral and human DNA polymerases and thus DNA synthesis. Herpesviral enzymes are ~20-fold more susceptible to the drug than host DNA. Vidarabine is administered IV in large volumes of fluid and is rapidly inactivated. It may produce bone marrow suppression and CNS adverse effects when high blood levels are reached. An ophthalmic solution also is available.