Intravenous
acyclovir is effective for
varicella in adults and immunocompromised children, causing more rapid resolution of the illness and fewer complications. Intravenous
acyclovir in immunocompromised patients with
herpes zoster decreases new lesion formation, decreases
acute pain, halts dissemination of the virus, and lessens visceral complications. Intravenous
acyclovir may also be effective in
zoster encephalitis. Intravenous
vidarabine also has a favorable affect on
chickenpox and
herpes zoster. Topical
acyclovir may benefit
herpes zoster in immunosuppressed patients by accelerating cutaneous healing. Oral
acyclovir appears to be effective in
varicella and
zoster in immunocompromised patients. It is also effective in otherwise normal patients, but its effect seems less dramatic and the
drug must be given early. Neither
acyclovir nor
vidarabine has been proven clearly to prevent
postherpetic neuralgia. Because varicella zoster virus is less sensitive to
acyclovir than is
herpes simplex, intravenous doses of 500 mg/m2 or 10 mg/kg every 8 hours or oral doses of 800 mg five times a day are recommended. At these doses adequate hydration and urine flow must be maintained, the mental status of the patient must be monitored, and impaired renal function requires regulation of dosage downward.