Trisodium phosphonoformate (foscarnet) is a po¬tent antiviral agent for treating herpes simplex infec¬tions. It works by affecting

Trisodium phosphonoformate (foscarnet) inhibits herpes simplex virus (HSV) replication. Foscarnet is a potent inhibitor of HSV-induced DNA polymerase, and has little effect on known cellular DNA polymer­ases. Herpesvirus mutants resistant to the drug arise easily. To a lesser extent, foscarnet also appears to inhibit the polymerase of hepatitis B virus and retroviruses. Combinations of antivirals, including foscarnet, are currently prescribed to increase the clinical usefulness of the drugs.