Famciclovir
Famciclovir (fam SYE kloe veer) is a generic medication prescribed to treat cold sores, genital herpes, and shingles. Famciclovir belongs to a group of drugs called deoxynucleoside analog DNA polymerase inhibitors.
Famciclovir (fam SYE kloe veer) is a generic medication prescribed to treat cold sores, genital herpes, and shingles. Famciclovir belongs to a group of drugs called deoxynucleoside analog DNA polymerase inhibitors.
- Generic
- • Tablet
- • 500mg
- • 21 Tablets
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Intro
Introduction
Written by Melanie Sangobowale, PharmD
Medically reviewed by Melissa Badowski, PharmD, MPH, FCCP
Updated on September 8, 2023
Famciclovir (fam SYE kloe veer) is a generic medication prescribed to treat cold sores, genital herpes, and shingles. Famciclovir belongs to a group of drugs called deoxynucleoside analog DNA polymerase inhibitors.
Side effects
Side effects of famciclovir
Famciclovir may cause mild or serious side effects. More common mild side effects of famciclovir and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.
To learn more about famciclovir’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for famciclovir listed in the “Resources” section.
Mild side effects
More common mild side effects reported with famciclovir are listed below. This article doesn’t include all possible mild side effects of the drug.
With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.
Famciclovir oral tablet’s mild side effects include:
- headache
- nausea
- diarrhea
- mild allergic reaction*
* For details about this side effect, see the “Interactions and warnings for famciclovir” section.
Serious side effects
Serious side effects of famciclovir are listed below.
This article doesn’t include all possible serious side effects of the drug. To learn more about famciclovir’s side effects, refer to the prescribing information for famciclovir listed in the “Resources” section.
With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.
In general, famciclovir’s serious side effects include:
- itchiness
- skin rash
- severe allergic reaction*
* For details about this side effect, see the “Interactions and warnings for famciclovir” section.
Uses
Uses of famciclovir
The Food and Drug Administration (FDA) approves prescription drugs such as famciclovir oral tablet for certain conditions. Approved uses for famciclovir oral tablet are described below.
Use for shingles, cold sores, and genital herpes
Doctors may prescribe famciclovir oral tablet for treating cold sores, genital herpes, and shingles in adults. It’s usually prescribed as a short-term treatment.
Cold sores, genital herpes, and shingles are caused by viruses. Specifically:
- Cold sores, also called oral herpes, are caused by the herpes simplex virus 1 (HSV-1). With cold sores, you develop a lesion (blister) around your mouth that may tingle, burn, or itch.
- Genital herpes is caused by HSV-2. It’s a sexually transmitted infection (STI) that causes painful, swollen, or itchy blisters around your genitals.
- Shingles is caused by the varicella-zoster virus. With shingles, you have a painful and burning skin rash that usually appears on one side of the body.
Doctors may not prescribe famciclovir oral tablet in certain situations, such as when:
- you have ophthalmic herpes zoster (a shingles rash located in and around the eye)
- you are experiencing the first episode of genital herpes
- you have a weakened immune system* and are currently receiving treatment for repeated episodes of genital herpes or cold sores
- you are Black or African American and have repeated episodes of genital herpes
* This does not include if you have human immunodeficiency virus (HIV).
FAQ
Common questions about famciclovir
Below you’ll find answers to a few commonly asked questions about famciclovir.
How does famciclovir work? And how long does it take to start working?
Famciclovir belongs to a group of drugs called deoxynucleoside analog DNA polymerase inhibitors. These drugs work by stopping the spread of the herpes virus in your body. Famciclovir is a prodrug. This means that once you take this drug by mouth, it changes into an active drug called penciclovir. An active drug is the ingredient that makes a medication work.
It usually takes 1–3 days for your symptoms to ease after you take famciclovir.
If you’d like to know more about this, talk with your doctor or pharmacist.
Is famciclovir similar to Valtrex?
Yes, famciclovir is similar to valacyclovir (Valtrex). They belong to the same group of medications, called deoxynucleoside analog DNA polymerase inhibitors. They work by stopping the spread of the herpes virus in your body. Both drugs are used to treat cold sores, genital herpes, and shingles in adults. Valtrex can also be used to treat chickenpox and cold sores in children.
Similar to famciclovir, Valtrex is a prodrug. Once you take Valtrex by mouth, it’s converted to acyclovir, the active drug. An active drug is the ingredient that makes the medication work.
For more information about how famciclovir compares with Valtrex, talk with your doctor or pharmacist.
Interactions and warnings
Interactions and warnings for famciclovir
Below you’ll find information about famciclovir’s possible interactions and warnings.
Interactions of famciclovir
Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.
Before you take famciclovir, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:
- prescription or over-the-counter drugs
- vitamins, herbs, or supplements
To learn about drug-condition interactions, see the “Warnings for famciclovir” section below.
Warnings for famciclovir
Famciclovir should be taken cautiously by certain people. The drug could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether famciclovir is a safe option for you.
Ask your doctor about specific warnings for famciclovir, and be sure to tell your doctor about your:
- current health, including any allergies to medications
- past health conditions or surgeries
Allergic reaction
Famciclovir can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.
If you’ve had an allergic reaction to famciclovir or any of its ingredients, your doctor will likely not prescribe famciclovir. They can tell you about medications that are safer options for you.
A mild allergic reaction may cause the following symptoms:
A severe allergic reaction may cause the following symptoms:
- swelling under your skin, usually in your hands, feet, eyelids, or lips
- swelling of your mouth, throat, or tongue, which can cause breathing problems
If you have an allergic reaction to famciclovir, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.
Overdose of famciclovir
If you take famciclovir by mouth, you should not take more famciclovir than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.
If you think you’ve taken too much famciclovir, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.
Pregnancy or breastfeeding and famciclovir
Information about famciclovir and pregnancy and breastfeeding is described below.
Famciclovir and pregnancy
There are risks to taking famciclovir oral tablet during pregnancy. But there are also risks with having untreated genital herpes while pregnant. (Keep in mind that famciclovir is used for treating genital herpes among other uses. For details, see the “Uses of famciclovir” section.)
If you’re planning a pregnancy or can become pregnant, talk with your doctor about treatment options for genital herpes during pregnancy. Together, you can discuss the risks and benefits of your treatment options and decide whether or not you should take famciclovir during pregnancy.
Famciclovir and breastfeeding
It’s not known whether famciclovir oral tablet should be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication.
If you’re planning to breastfeed, talk with your doctor about treatment options for genital herpes. Together, you can discuss the risks and benefits of your treatment options and decide whether or not you should take famciclovir during this time. Your doctor may recommend other healthy ways to feed your child.
Ask your doctor
What to ask your doctor
Let your doctor know if you have questions about famciclovir or would like more details about it.
Here’s a list of some possible questions you may want to ask your doctor:
- Can I crush famciclovir oral tablet if I have difficulty swallowing it?
- Will taking famciclovir cure my cold sores?
- Do I have to take famciclovir every day?
Resources
Resources
- Famciclovir tablets, for oral use. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/3f02042f-8f51-4ccf-b608-5dcd75d100fb/spl-doc
- Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
- Valtrex (valacyclovir) tablets, for oral use. (2022). https://gskpro.com/content/dam/global/hcpportal/en_US/Prescribing_Information/Valtrex/pdf/VALTREX-PI-PIL.PDF
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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