What is Famciclovir used for?
Famciclovir is commonly used to treat infections caused by certain types of viruses. It treats shingles caused by herpes zoster. It also treats outbreaks of herpes simplex that cause cold sores around the mouth, sores around the anus, and genital herpes. In people with frequent outbreaks of genital herpes, famciclovir is used to help reduce the number of future episodes.
Famciclovir is an antiviral drug. However, it is not a cure for these infections. The viruses that cause these infections continue to live in the body even between outbreaks. Famciclovir decreases the severity and length of these outbreaks. It helps the sores heal faster, keeps new sores from forming, and decreases pain/itching. This medication may also help reduce how long pain remains after the sores heal. In addition, in people with a weakened immune system, famciclovir can decrease the risk of the virus spreading to other parts of the body and causing serious infections.
How should I take Famciclovir?
Take this medication by mouth with or without food, usually 2 to 3 times a day or as directed by your doctor.
This medication works best when started at the first sign of an outbreak, as directed by your doctor. It may not work as well if you delay treatment.
The dosage is based on your medical condition and response to treatment.
This medication works best when the amount of drug in your body is kept at a constant level. Therefore, take this drug at evenly spaced intervals. To help you remember, take it at the same times each day.
Continue to take this medication until the full prescribed amount is finished. Do not change your dose, skip any doses, or stop this medication early without your doctor’s approval.
Tell your doctor if your condition persists or worsens.
How do I store Famciclovir?
Famciclovir is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Famciclovir in the bathroom or the freezer. There may be different brands of Famciclovir that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.
You should not flush Famciclovir down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.
Precautions & warnings
What should I know before using Famciclovir?
Before taking famciclovir, tell your doctor or pharmacist if you are allergic to it; or to penciclovir; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney problems.
This drug may rarely make you dizzy or drowsy. Alcohol or marijuana can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana.
This medication may contain lactose. If you have certain conditions such as galactose intolerance, severe lactase deficiency (not lactose or milk intolerance), or glucose-galactose malabsorption that require you to restrict your intake of lactose, consult your doctor or pharmacist before taking this medication.
Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).
Do not have certain immunizations/vaccinations (such as vaccines against the varicella virus) without the consent of your doctor.
Older adults may be more sensitive to the side effects of this drug, especially dizziness, drowsiness, confusion, and change in the amount of urine (kidney problems).
Famciclovir does not protect against the spread of genital herpes. To lower the chance of giving herpes to your partner, do not have sexual contact during an outbreak or if you have symptoms. You can spread genital herpes even if you do not have symptoms. Therefore, always use an effective barrier method (latex or polyurethane condoms/dental dams) during all sexual activity. Consult your doctor or pharmacist for more details.
During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.
It is unknown if this medication passes into breast milk. It may have undesirable effects on a nursing infant. Consult your doctor before breast-feeding.
Is it safe during pregnancy or breast-feeding?
There are no adequate studies in women for determining risk when using this Famciclovir during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking Famciclovir. Famciclovir is pregnancy risk category B according to the US Food and Drug Administration (FDA).
FDA pregnancy risk category reference below:
- A=No risk,
- B=No risk in some studies,
- C=There may be some risk,
- D=Positive evidence of risk,
What side effects can occur from Famciclovir?
Headache, nausea, and diarrhea may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: mental/mood changes (such as agitation, slowed thinking, confusion, hallucinations), dizziness, drowsiness, signs of kidney problems (such as change in the amount of urine), yellowing eyes/skin, easy bruising/bleeding.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.
What drugs may interact with Famciclovir?
Famciclovir may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.
Does food or alcohol interact with Famciclovir?
Famciclovir may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.
What health conditions may interact with Famciclovir?
Famciclovir may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.
The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this Famciclovir.
What is the dose of Famciclovir for an adult?
Usual Adult Dose for Herpes Simplex – Mucocutaneous/Immunocompetent Host
Initial episode: 250 mg orally 3 times a day for 7 to 10 days has been recommended by the US Centers for Disease Control and Prevention (CDC)
Recurrent episodes: 1000 mg orally twice a day for 1 day; alternatively, 125 mg orally twice a day for 5 days has been recommended by the CDC
Famciclovir should be started at the first sign or symptom of a recurrent episode (such as tingling, burning, itching, pain, or lesion). The efficacy has not been established if started more than 6 hours after onset of symptoms or lesions.
Usual Adult Dose for Herpes Simplex – Mucocutaneous/Immunocompromised Host
Recurrent episodes of orolabial or genital herpes in HIV-infected patients: 500 mg orally twice a day for 7 days (5 to 10 days recommended by the CDC)
Famciclovir should be started at the first sign or symptom of a recurrent episode (such as tingling, burning, itching, pain, or lesion). The efficacy has not been established if started more than 48 hours after onset of symptoms or lesions.
Usual Adult Dose for Herpes Simplex – Suppression
Chronic suppression of recurrent genital herpes:
Immunocompetent patients: 250 mg orally twice a day
HIV-infected patients: 500 mg orally twice a day has been recommended by the CDC
Therapy should be continued as clinically appropriate, although the safety and efficacy of famciclovir therapy beyond 1 year have not been established.
Usual Adult Dose for Herpes Zoster
500 mg orally every 8 hours for 7 days
Famciclovir is most effective if started within 48 hours of onset of rash. The efficacy has not been established if started more than 72 hours after onset of rash.
Usual Adult Dose for Herpes Simplex Labialis
Recurrent herpes labialis: 1500 mg orally as a single dose
Famciclovir is most effective if started at the earliest sign or symptom of a cold sore (such as tingling, burning, itching, pain, or lesion).
Renal Dose Adjustments
CrCl 40 to 59 mL/min:
Recurrent genital herpes, immunocompetent patient: 500 mg orally every 12 hours for 1 day
Herpes zoster: 500 mg orally every 12 hours
Recurrent herpes labialis: 750 mg orally once as a single dose
CrCl 20 to 39 mL/min:
Recurrent genital herpes, immunocompetent patient: 500 mg orally once as a single dose
Suppression of recurrent genital herpes, immunocompetent patient: 125 mg orally every 12 hours
Recurrent orolabial and genital herpes, HIV-infected patient: 500 mg orally every 24 hours
Herpes zoster: 500 mg orally every 24 hours
Recurrent herpes labialis: 500 mg orally once as a single dose
CrCl less than 20 mL/min:
Recurrent genital herpes, immunocompetent patient: 250 mg orally once as a single dose
Suppression of recurrent genital herpes, immunocompetent patient: 125 mg orally every 24 hours
Recurrent orolabial and genital herpes, HIV-infected patient: 250 mg orally every 24 hours
Herpes zoster: 250 mg orally every 24 hours
Recurrent herpes labialis: 250 mg orally once as a single dose
Liver Dose Adjustments
Mild or moderate hepatic impairment: No adjustment recommended.
Severe hepatic impairment: Data not available
Efficacy and safety have not been determined for initial genital herpes episodes, ophthalmic zoster, Black and African American patients with recurrent genital herpes, or immunocompromised patients other than for the treatment of recurrent orolabial or genital herpes in HIV-infected patients.
The dosage should be reduced in patients with renal dysfunction. Acute renal failure has developed in patients with renal disease who received larger than recommended doses of famciclovir.
Caution should be exercised in the administration and monitoring of famciclovir in the elderly reflecting the greater frequency of decreased renal function and concomitant use of other drugs.
Since the tablets contain lactose, individuals who have hereditary galactose intolerance, severe lactase deficiency, or glucose-galactose malabsorption should check with their healthcare provider before taking famciclovir.
Recurrent genital herpes, immunocompetent patient: 250 mg orally as a single dose following dialysis
Suppression of recurrent genital herpes, immunocompetent patient: 125 mg orally following each dialysis
Recurrent orolabial and genital herpes, HIV-infected patient: 250 mg orally following each dialysis
Herpes zoster: 250 mg orally following each dialysis
Recurrent herpes labialis: 250 mg orally as a single dose following dialysis
Famciclovir may be given without regard to meals.
Patients should be aware that famciclovir is not a cure for cold sores or genital herpes. There are no data on whether it will prevent transmission of genital herpes to others.
Patients should be advised against driving or operating machinery if dizziness, somnolence, confusion, or other CNS side effects develop.
What is the dose of Famciclovir for a child?
The dosage has not been established in pediatric patients. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.
How is Famciclovir available?
Famciclovir is available in the following dosage forms and strengths:
- Oral Tablet
What should I do in case of an emergency or overdose?
In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.
What should I do if I miss a dose?
If you miss a dose of Famciclovir, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: January 30, 2018 | Last Modified: September 12, 2019
Famciclovir. https://www.webmd.com/drugs/2/drug-6157/famciclovir-oral/details. Accessed January 30, 2018.
Famciclovir Dosage. https://www.drugs.com/dosage/famciclovir.html. Accessed January 30, 2018.