The use of acyclovir in suspected encephalitis

The early use of intravenous acyclovir in herpes simplex encephalitis (HSE) is essential. However, rapid diagnostic tests are not freely available. Hence, all patients with suspected encephalitis may need to be commenced on acyclovir. In our study, of 34 patients with suspected encephalitis, only two eventually had HSE confirmed, 19 had encephalitis not due to herpes simplex and in 13 a non-encephalitis illness was finally diagnosed. Guidelines for the use of acyclovir in suspected encephalitis are given aimed at minimizing the drug cost whilst still protecting all cases of presumed HSE.