Absence of idoxuridine and persistence of herpes simplex virus in brains of patients being treated for encephalitis.

Thirty-two specimens of brain from five patients with encephalitis suspected to be caused by herpes simplex virus, type 1 (HSV-1) were assayed for antiviral activity. Each patient received 60-80 mg/kg/day of idoxuridine (IDU) by intravenous infusion. The antiviral assay does not measure anti-HSV-1 antibodies. Biopsies of brain in every patient taken before IDU was used, and portions of several regions of the brain at autopsy were available during courses of treatment in four of the five patients. The last patient died 7 days after completing treatment. A significant concentration of IDU (833 mug/ml) was measured transiently in the cerebrospinal fluid of one patient. Meninges and brains showed inflammatory changes. Within the sensitivity of the test (larger than or equal to 6 mug/g) all specimens contained no IDU. As given, IDU does not achieve therapeutic concentrations in human brain. Further clinical use of IDU in therapy of herpes simplex virus encephalitis is not indicated.