Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: famciclovir
BRAND NAME: Famvir
DRUG CLASS AND MECHANISM: Famciclovir is an antiviral drug which is
active against the Herpes viruses, including herpes simplex 1 and 2 (cold sores
and genital herpes) and varicella-zoster (shingles and
chickenpox). It belongs
to a class of drugs called nucleoside analogs that mimic one of the building
blocks of DNA. It stops the spread of herpes virus in the body by preventing the
replication of viral DNA that is necessary for viruses to multiply. Other drugs
in the same class include acyclovir (Zovirax) and valacyclovir (Valtrex).
Famciclovir is actually a "prodrug," that is, not active directly against
viruses. Instead, famciclovir is converted to penciclovir in the body, and it is
the penciclovir that is active against the viruses. Famciclovir is active
against the same viruses as acyclovir but has a longer duration of action.
Therefore, it can be taken fewer times each day. Famciclovir does not cure or
stop the spread of herpes infections. Famciclovir relieves pain, burning,
itching, tingling, and heals and prevents sores associated with herpes
infections. Famciclovir was approved for use by the FDA in June 1994.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets: 125, 250, 500 mg
STORAGE: Famciclovir should be stored at room temperature, 15-30 C
(59-86 F).
PRESCRIBED FOR: Famciclovir is used for the treatment of
genital
herpes and cold sores in patients with normal immune systems and
HIV-infected
individuals. It also is used for treating shingles. To be most effective,
famciclovir should be started as soon as possible after the diagnosis of a
herpes infection.
DOSING: Famciclovir may be taken with or without food. The recommended
doses are outlined below:
- Recurrent genital herpes: 1,000 mg twice daily for 1 day.
- Recurrent cold
sores: 1,500 mg as a single dose.
- Suppression of recurrent genital herpes: 250
mg twice daily for up to 1 year.
- Shingles: 500 mg every 8 hours for 7 days.
- HIV-infected patients (cold sores or genital herpes): 500 mg twice daily for
5-10 days.
DRUG INTERACTIONS: Probenecid (Benemid) may reduce the kidney's
removal of famciclovir leading to higher concentrations of famciclovir in the
blood. This may lead to side effects from famciclovir.
PREGNANCY: Famciclovir has not been adequately studied in
pregnant
women.
NURSING MOTHERS: It is not known if famciclovir is excreted into human
breast milk. Women may wish to consider an alternative to
breastfeeding if
famciclovir is taken while nursing.
SIDE EFFECTS: The most common side effects associated with the use of
famciclovir are headache, fatigue, nausea,
vomiting, rash, diarrhea and
flatulence. Serious but rare side effects include serious skin reactions, and
reduced white blood cells (neutropenia) or platelets (thrombocytopenia).
Reference: FDA Prescribing Information
Last Editorial Review: 3/23/2009
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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