Successful treatment of progressive acyclovir-resistant herpes simplex virus using intravenous foscarnet in a patient with the acquired immunodeficiency syndrome.

We report a case of orofacial herpes simplex virus (HSV) infection that was progressive despite multiple courses of acyclovir sodium in a patient with the acquired immunodeficiency syndrome. The viral isolate was shown to be resistant to acyclovir in vitro, but proved susceptible to vidarabine and foscarnet sodium (trisodium phosphonoformate). The patient failed to respond to a 2-week course of intravenous vidarabine. However, rapid improvement in the orofacial lesion occurred with intravenous foscarnet. Most HSV isolates that are resistant to acyclovir are spontaneous mutants partially or completely lacking in thymidine kinase. Because foscarnet is a direct inhibitor of HSV DNA polymerase, this compound is expected to have efficacy against acyclovir-resistant strains. This report documents successful treatment of clinically significant HSV with intravenous administration of foscarnet, suggesting that further study is indicated.