Famciclovir

Famciclovir comes as a tablet to take by mouth with or without food. When famciclovir is used to treat shingles, it is usually taken every 8 hours (three times a day) for 7 days, starting within 3 days after the rash begins to appear. When famciclovir is used to treat cold sores and fever blisters, it is usually taken as one dose at the earliest sign or symptom (tingling, itching, or burning) of a cold sore. When famciclovir is used to treat repeat outbreaks of genital herpes, it is usually taken twice a day for one day, starting within 6 hours of the first sign or symptom of the condition. To keep genital herpes from returning, famciclovir is usually taken twice a day for up to 1 year. When famciclovir is used to treat herpes infection in people infected with HIV, it is usually taken twice a day for 7 days. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take famciclovir exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Use this medication as soon as possible after symptoms appear.

Continue to take famciclovir even if you feel well. Do not stop taking famciclovir without talking to your doctor.

Before taking famciclovir,

• tell your doctor and pharmacist if you are allergic to famciclovir, penciclovir cream (Denavir), acyclovir (Zovirax), any other medications, or lactose.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplement, and herbal products you are taking or plan to take, especially probenecid (Benemid).
• tell your doctor if you have or have ever had problems with your immune system, human immunodeficiency virus infection (HIV), or acquired immunodeficiency syndrome (AIDS); galactose intolerance or glucose-galactose malabsorption (inherited conditions where the body is not able to tolerate lactose); or kidney or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking famciclovir, call your doctor.
• you should know that famciclovir may make you drowsy, dizzy, confused, or disoriented. Do not drive a car or operate machinery until you know how this medication affects you.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

• Famvir^®

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.

Herpes infections are contagious and you can infect other people, even while you are being treated with famciclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Famciclovir will not prevent the spread of genital herpes. Avoid sexual intercourse or use a latex condom to prevent spreading the virus to others.

This medication may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Tell your doctor about all other medicines you use, especially:

• probenecid (Benemid); or
• other medications you use to treat herpes outbreaks, such as acyclovir (Zovirax), valacyclovir (Valtrex), and others.

There may be other drugs that can interact with famciclovir. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

Appropriate symptomatic and supportive therapy should be given. Penciclovir is removed by hemodialysis.

The most common side effects of famciclovir include:

• headache
• nausea

Talk to your healthcare provider if you have any side effect that bothers you or that does not go away. 

These are not all the possible side effects of famciclovir. Ask your healthcare provider or pharmacist for more information.

Call your healthcare provider for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your healthcare provider if you are breastfeeding or plan to breastfeed. It is not known if famciclovir is excreted in human breast milk or if it will harm your nursing baby.

If you take too much famciclovir, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Your pharmacist can provide more information about famciclovir.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

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You should not take this medication if you are allergic to famciclovir or penciclovir cream (Denavir).

Take this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared.

Treatment with famciclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Herpes infections are contagious and you can infect other people, even while you are being treated with famciclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Storage

Oral

15–30°C.1

• Famciclovir is the diacetyl 6-deoxy analog of penciclovir.1 Prodrug with no antiviral activity until converted in vivo to penciclovir and subsequently to the active penciclovir triphosphate.1 5 6 12 13 17

• Active against various Herpesviridae including herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and Epstein-Barr virus (EBV).1 5 6 7 8 9 12 13 17 Also active against hepatitis B virus (HBV).29 30 31 32 33 34 Only limited activity in vitro against cytomegalovirus (CMV).6 9 17

• Penciclovir triphosphate exerts its antiviral activity by interfering with DNA synthesis; the drug competes with deoxyguanosine triphosphate for viral DNA polymerase, inhibits DNA chain elongation, and inhibits viral replication.1

• Resistance to penciclovir reported in HSV and VZV.1

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• Black, tarry stools
• bleeding gums
• blistering, peeling, or loosening of the skin
• blood in urine or stools
• chills
• clay-colored stools
• cough
• dark urine
• dizziness
• fever
• joint or muscle pain
• loss of appetite
• pinpoint red spots on the skin
• red, irritated eyes
• sore throat
• sores, ulcers, or white spots in the mouth or on the lips
• unpleasant breath odor
• unusual bleeding or bruising
• vomiting of blood
• yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

• Cramps
• diarrhea
• headache
• heavy bleeding
• nausea
• stomach pain

• Bloated, full feeling
• burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feeling
• confusion as to time, place, or person
• excess air or gas in the stomach or intestines
• hives or welts
• holding false beliefs that cannot be changed by fact
• itching skin
• mood or mental changes
• passing gas
• rash
• redness of skin
• seeing, hearing, or feeling things that are not there
• unusual excitement, nervousness, or restlessness
• unusual tiredness or weakness
• vomiting

• Sleepiness or unusual drowsiness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Acute renal failure

Cases of acute renal failure have been reported in patients with underlying renal disease who have received inappropriately high doses of Famciclovir tablets for their level of renal function. Dosage reduction is recommended when administering Famciclovir tablets to patients with renal impairment [see Dosage and Administration (2.3), Use in Specific Populations (8.6)].

Treatment of acute herpes zoster (shingles) in immunocompetent patients; treatment and suppression of recurrent episodes of genital herpes in immunocompetent patients; treatment of herpes labialis (cold sores) in immunocompetent patients; treatment of recurrent orolabial/genital (mucocutaneous) herpes simplex in HIV-infected adult patients

Refer to adult dosing.

Herpes zoster:

CrCl ≥60 mL/minute: No dosage adjustment necessary.

CrCl 40 to 59 mL/minute: Administer 500 mg every 12 hours

CrCl 20 to 39 mL/minute: Administer 500 mg every 24 hours

CrCl <20 mL/minute: Administer 250 mg every 24 hours

Hemodialysis: Administer 250 mg after each dialysis session.

Recurrent genital herpes: Treatment:

Single-day regimen:

CrCl ≥60 mL/minute: No dosage adjustment necessary.

CrCl 40 to 59 mL/minute: Administer 500 mg every 12 hours for 1 day

CrCl 20 to 39 mL/minute: Administer 500 mg as a single dose

CrCl <20 mL/minute: Administer 250 mg as a single dose

Hemodialysis: Administer 250 mg as a single dose after a dialysis session.

Alternatively the following recommendations have been made (Famvir Canadian product labeling 2016):

CrCl >20 mL/minute/1.73 m2: Administer 125 mg every 12 hours

CrCl <20 mL/minute/1.73 m2: Administer 125 mg every 24 hours

Hemodialysis: Administer 125 mg after each dialysis session.

Recurrent genital herpes: Suppression:

CrCl ≥40 mL/minute: No dosage adjustment necessary.

CrCl 20 to 39 mL/minute: Administer 125 mg every 12 hours

CrCl <20 mL/minute: Administer 125 mg every 24 hours

Hemodialysis: Administer 125 mg after each dialysis session.

Recurrent herpes labialis: Treatment (single-dose regimen):

CrCl ≥60 mL/minute: No dosage adjustment necessary.

CrCl 40 to 59 mL/minute: Administer 750 mg as a single dose

CrCl 20 to 39 mL/minute: Administer 500 mg as a single dose

CrCl <20 mL/minute: Administer 250 mg as a single dose

Hemodialysis: Administer 250 mg as a single dose after a dialysis session.

Recurrent orolabial/genital (mucocutaneous) herpes in HIV-infected patients:

CrCl ≥40 mL/minute: No dosage adjustment necessary.

CrCl 20 to 39 mL/minute: Administer 500 mg every 24 hours

CrCl <20 mL/minute: Administer 250 mg every 24 hours

Hemodialysis: Administer 250 mg after each dialysis session.