Oral and intravenous acyclovir are equally effective in herpes zoster.

In a double-blind randomised trial 40 patients above 60 years old with acute herpes zoster received either 5 mg/kg acyclovir three times daily intravenously or 400 mg acyclovir five times daily orally for five days. Identical results were obtained with respect to duration of pain and rate of healing. Twenty per cent of orally administered acyclovir was absorbed and gave satisfactory concentrations of acyclovir in the vesicular fluid.