791 Pill - white round, 11mm Pill with imprint 791 is White, Round and has been identified as Acyclovir 400 mg. It is supplied by Zydus Pharmaceuticals (USA) Inc.Acyclovir is used in the treatment of Herpes Simplex (HSV); Cold Sores; Herpes Simplex Encephalitis; Herpes Simplex - Congenital...