Detailed Drug Information:

DRUG CLASS AND MECHANISM: Valacyclovir is an oral antiviraldrug which is active against the Herpes viruses. It is used to treat infectionswith herpes zoster (shingles ), herpes simplex genitalis (genital herpes), and herpes labialis (cold sores).Valacyclovir inhibits the replication of viral DNA which is necessary forviruses to reproduce themselves. Valacyclovir is actually a "prodrug,"in that it is not active itself. Rather, it is converted to acyclovir in the body, and it is the acyclovir that is active against the viruses. (Acyclovir itself is available as a topical, oral and intravenous medication.) Valacyclovir, therefore, is active against the same viruses as acyclovir, but valacyclovir has a longer duration of action than acyclovir, and, therefore, can be taken fewer times each day. Valacyclovirwas approved for use by the FDA in 1995.

PREPARATIONS: Caplets (blue): 500mg.

STORAGE: Valacyclovir should be kept between 2° and 30°C(36-86°F).

PRESCRIBED FOR: Valacyclovir is used to treat infectionswith herpes zoster (shingles), herpes simplex genitalis (genital herpes), andherpes labialis (cold sores).

DOSING: Valacyclovir may be taken with or without food. Dosages need to be reduced in patients with kidney disease. For the treatment of herpes zoster (shingles), the usual dose is 1 gm three times a day for 7 days. Treatment should begin at the first symptom and is most effective if started within 48 hours of the onset of rash.

For the treatment of an initial episode of herpes, theusual dose is 1 gm twice daily for 10 days. For the treatment ofrecurrent herpes, the usual dose is 500 mg twice daily for 5 days. Forbest results, treatment should be initiated within 12 hours of the startof symptoms.

DRUG INTERACTIONS: Probenecid (Benemid) and cimetidine (Tagamet)may reduce the kidney's clearance of Valacyclovir, leading to higherconcentrations in the blood. This may lead to side effects ofvalacyclovir.

PREGNANCY: Valacyclovir showed no effects on the fetus in animalstudies, however, there has been no adequate evaluation of valacyclovir or(acyclovir) in pregnant women. The incidence of birth defects in womentaking acyclovir is about the same as in the general population.Valacyclovir should only be used during pregnancy when the benefits to themother outweigh risks to the fetus.

NURSING MOTHERS: It is not known whether valacyclovir is excreted into breast milk. It is known, however, that among women takingacyclovir, concentrations of acyclovir in breast milk are about 4 timeshigher than in the mother's blood. The safety of valacyclovir inbreast-feeding infants has not been established. Methods other than breastfeeding should be considered if Valacyclovir must be taken while nursing.

SIDE EFFECTS: The side effect profile of valacyclovir is similarto that of acyclovir. The most commonly reported side effects areheadache, nausea, and vomiting. Less common side effects are diarrhea,abdominal pain, and dizziness.