Acyclovir treatment of experimental simian varicella infection of monkeys

Replication of simian varicella virus (SVV) in Vero cell cultures was inhibited by acyclovir, 9-(2-hydroxyethoxymethyl)guanine (ACV), at a concentration of 10 micrograms/ml in culture medium. Intravenous administration of ACV at 10 mg/kg twice a day for 10 days or 15 mg/kg three times a day for 5 days to patas monkeys (Erythrocebus patas) beginning 48 h after SVV inoculation blocked the appearance of rash and other clinical symptoms but did not affect viremia. ACV treatment of African green monkeys (Cercopithecus aethiops) at 10 mg/kg twice a day by intravenous injection beginning 24 or 72 h after SVV inoculation and continuing for 10 days had no effect on clinical symptoms, including the development of rash, or on the appearance of viremia. The minimal therapeutic results could be due to the observation that doses of 10 or 15 mg/kg produced plasma levels of ACV which were lower than 5 micrograms/ml, the concentration that inhibited SVV multiplication in vitro, and decayed rapidly.