Medications and Drugs
GENERIC NAME: valacyclovir
BRAND NAME: Valtrex
DRUG CLASS AND MECHANISM: Valacyclovir is an oral
antiviral
drug which is active against the herpes viruses. It is used to treat
infections
with herpes zoster (shingles
), herpes simplex genitalis (genital herpes), and herpes labialis (cold
sores).
Valacyclovir inhibits the replication of viral DNA which is
necessary for
viruses to reproduce themselves. Valacyclovir is actually a
"prodrug,"
in that it is not active itself. Rather, it is converted to
acyclovir (Zovirax)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. Valacyclovir
was approved for use by the FDA in 1995.
PRESCRIPTION: yes
GENERIC AVAILABLE: no
PREPARATIONS: Caplets (blue): 500mg.
STORAGE: Valacyclovir should be kept between 2 and
30 C
(36 and 86 F).
PRESCRIBED FOR:
Valacyclovir is used
to treat infections
with herpes zoster (shingles), herpes simplex genitalis (genital herpes),
and
herpes 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, the
usual dose is 1 gm twice daily for 10 days. For the treatment
of
recurrent herpes, the usual dose is 500 mg twice daily for 5
days. For
best results, treatment should be initiated within 12 hours of
the start
of symptoms.
DRUG INTERACTIONS: Probenecid (Benemid) and cimetidine
(Tagamet)
may reduce the kidney's clearance of valacyclovir, leading to
higher
concentrations in the blood. This may lead to side effects of
valacyclovir.
PREGNANCY: Valacyclovir showed no effects on the fetus
in animal
studies, however, there has been no adequate evaluation of
valacyclovir or
(acyclovir) in pregnant women. The incidence of birth defects
in women
taking acyclovir is about the same as in the general population.
Valacyclovir should only be used during pregnancy when the
benefits to the
mother 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 taking
acyclovir, concentrations of acyclovir in breast milk are about
four times
higher than in the mother's blood. The safety of valacyclovir in
breast-feeding infants has not been established. Methods other
than breast
feeding should be considered if Valacyclovir must be taken while
nursing.
SIDE EFFECTS: The side effect profile of valacyclovir
is similar
to that of acyclovir. The most commonly reported side effects
are
headache, nausea, and vomiting. Less common side effects are
diarrhea,
abdominal pain, and dizziness.
Reference: FDA Prescribing Information
Last Editorial Review: 9/20/2002
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
- Shingles - Read about shingles symptoms (contagious rash), vaccine, causes (chickenpox [varicella] virus, stress), treatment, how it's transmitted and postherpetic neuralgia.
- acyclovir, Zovirax - Explains the medication acyclovir (Zovirax), a drug used to treat initial genital herpes infections and to treat patients with recurrent severe genital herpes.
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