Tromantadine hydrochloride, an Amantadine derivative with antiherpetic activity, inhibits herpes simplex virus type 1 (HSV-1) and HSV-2 replication.In Vitro: Treatment of the cells with 10 to 50μg of Tromantadine reduces HSV-induced cytopathic effect. Treatment with 100 to 500μg of Tromantadine inhibits herpes simplex virus-induced cytopathic effect and reduces virus production. Complete inhibition of virus production is observed with treatments of 500μg to 1 mg. The antiherpetic activity of Tromantadine is dependent upon the viral inoculum size and the time of addition of the compound with respect to infection.