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- What is famciclovir, and how does it work (mechanism of action)?
- What brand names are available for famciclovir?
- Is famciclovir available as a generic drug?
- Do I need a prescription for famciclovir?
- What are the side effects of famciclovir?
- What is the dosage for famciclovir?
- Which drugs or supplements interact with famciclovir?
- Is famciclovir safe to take if I'm pregnant or breastfeeding?
- What else should I know about famciclovir?
What is famciclovir, and how does it work (mechanism of action)?
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, and tingling, and also heals and prevents sores associated with herpes infections. Famciclovir was approved for use by the FDA in June 1994.
What are the side effects of famciclovir?
The most common side effects associated with the use of famciclovir are:
Other important side effects which are serious, but rare, include
- serious allergic reactions,
- serious skin reactions,
- abnormal tests of liver function, and
- reduced white blood cells (neutropenia) or platelets (thrombocytopenia).
Cases of kidney failure have been reported when higher than recommended doses of famciclovir were administered to patients with underlying kidney problems.
What is the dosage for famciclovir?
Famciclovir may be taken with or without food. The recommended doses are:
- Recurrent genital herpes: 1,000 mg every 12 hours for one day.
- Recurrent cold sores: 1,500 mg as a single dose.
- Suppression of recurrent genital herpes: 250 mg twice daily.
- Shingles: 500 mg every 8 hours for 7 days.
- HIV-infected patients (cold sores or genital herpes): 500 mg twice daily for 7 days.
Which drugs or supplements interact with famciclovir?
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.
Is famciclovir safe to take if I'm pregnant or breastfeeding?
Famciclovir has not been adequately studied in pregnant women.
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.
Famciclovir (Famvir) is a drug used for the treatment of genital herpes, cold sores, shingles, and chickenpox. Side effects, drug interactions, warnings and precautions, and pregnancy information should be reviewed prior to taking this medication.
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