Acyclovir‐Resistant Herpes Zoster in Human Immunodeficiency Virus– Infected Patients: Results of Foscarnet Therapy

We retrospectively studied 18 consecutive cases of acyclovir-resistant zoster. All the patients had chronic skin lesions that failed to heal despite treatment with intravenous acyclovir (30 mg/[kg.d]) in 15 cases and oral acyclovir (4 g/d) in three cases for > 10 days. The mean CD4+ cell count was 20 x 10(6)/L. The mean number of previous zoster episodes was 1.53. Fifteen of the 16 patients evaluable for previous acyclovir treatment had received the drug. Thirteen patients were treated with intravenous foscarnet (200 mg/[kg.d]) for a mean of 17.8 days. Complete healing was observed in 10 (77%) of the 13 treated patients. Zoster relapsed after cessation of foscarnet therapy in five of the 10 responding patients. The median time to relapse was 110 days. Four patients died of varicella-zoster virus-associated visceral complications. These results show that acyclovir-resistant zoster has a poor prognosis but responds well to foscarnet therapy.