Sorivudine (BV-araU) has antiviral activity against several viruses including varicella zoster virus, herpes simplex type 1 virus, and Epstein-Barr virus by interfering with viral DNA synthesis.

Sorivudine inhibits strains of HSV-1 and HSV-2 (ID50s (50% inhibitory dose): 0.39 and 0.67 μM, respectively). Sorivudine has antiviral activity against several viruses including varicella-zoster virus, herpes simplex type 1 virus, and Epstein-Barr virus. Sorivudine has in vitro inhibitory activity against the varicella-zoster virus at concentrations of 00001-0.004 mg/ml. These concentrations are over 1000-fold lower than those which are required for the inhibition of VZV replication by acyclovir 3 Sorivudine also inhibits HSV-I replication at concentrations ranging from 0.03-0.1 mg/ml [1][2].

Sorivudine has been evaluated in the treatment of HSV-l encephalitis when administered orally to mice. The survival of treated mice is prolonged at dosages in excess of 12.5 mg/kg. A significant decrease in mortality was achieved as well with doses in excess of 50 mg/kg. Sorivudine therapy at dosages as low as 20 mg/kg per day given intramuscularly or 100 mg/kg per day administered orally completely protected against viremia and mortality. There was no evidence of neurotoxicity or abnormalities in hematology or clinical chemistries. Doses as low as 0.2 mg/kg per day were effective; however, breakthrough viremia was noted at lower dosages [2].