Acyclovir, also sold under the brand name Zovirax®, is a prescription anti-viral medication used to treat infections by viruses within the herpes family. Its development was considered to have been a revolutionary discovery for which pharmacologist Gertrude B. Elion was awarded the Nobel Prize in Medicine. The drug is poorly absorbed orally, requiring either that large amounts be taken or that it be co-administered with the drug valaciclovir to achieve a sufficient acyclovir dose. Other factors that can affect acyclovir dose recommendations are the age of the patient to be treated as well as his or her level of kidney and immune system function.
When beginning a course of treatment for herpes simplex in a typical adult, 200 mg taken by mouth five times daily over a period of 10 days is recommended by the manufacturers. Alternatively, a dose of 400 mg may be taken three times a day. For herpes simplex affecting the lips, the dose may be taken for just five days.
While children 12 years of age and older may follow the acyclovir dose recommendations for adults, those between the three months and 11 years of age should use between 10 and 20 mg per kilogram of body weight four times daily. For infants fewer than three months old, an acyclovir dose of 10 mg per kilogram should be administered intravenously every eight hours for 10 to 21 days. Premature infants should receive no more than 10 mg intravenously every 12 hours.
The oral acyclovir dose for adult patients with lowered immune function is the same as that for patients with normal immune function, although the medication may be taken for up to 14 days. Alternatively, the drug may be administered intravenously at a dose of 5 mg/kg every eight hours for the same period of time. In children 12 years of age and older, the standard adult dosage can be used, while those between the ages of 3 months and 11 years of age should use 5 to 10 mg per kilogram of body weight.
One of the risks of acyclovir in patients with lowered kidney function is kidney failure. Before a patient at risk for kidney failure takes this medication, he or she should carefully consult an acyclovir dosage chart to determine the lowest possible sufficient dose for the treatment of his or her condition. Dosage adjustments for impairments in kidney function are comparable in children to those in adults. Diminished liver function, however, does not appear to affect the metabolism of the drug and does not require any adjustment to the recommended dose.