Increased efficacy of ganciclovir in combination with foscarnet against cytomegalovirus and herpes simplex virus type 2 in vitro and in vivo

In tissue culture, efficacy against either murine CMV or HSV-2 was increased 27-fold for the acyclic nucleoside ganciclovir and 3-fold for foscarnet (trisodium phosphonoformate) when the 2 drugs were combined; whereas against human CMV, efficacy was increased 3-fold for both drugs. In mice, efficacy was increased 2-fold for ganciclovir and 4- to 5-fold for foscarnet when used in combination against either murine CMV or HSV-2. These results suggest an additive interaction between the two drugs in vivo.