Effect of combined acyclovir and vidarabine on infection with herpes simplex virus in vitro and in vivo.

Acyclovir and vidarabine exerted a less-than-additive effect on the replication of herpes simplex virus type 1 (HSV-1) in green monkey kidney cells. The synthesis of viral DNA was reduced much more (97%) than that of cellular DNA (45%) by combined acyclovir and vidarabine in cell culture. Furthermore, the combined drugs, given topically or systemically, were more effective than the individual drugs in diminishing the development of clinical signs of HSV-1 infection in hairless mice. However, mortality among animals given topical acyclovir plus vidarabine was not significantly lower than that among animals given topical acyclovir only. Systemic acyclovir (50 mg/kg per day) plus vidarabine (100 mg/kg per day), given for five consecutive days starting 24 hr after viral inoculation, significantly reduced the frequency of development of latent HSV-1 infection in the trigeminal ganglia of mice, whereas systemic acyclovir or vidarabine alone did not.