Description and Brand Names

Drug information provided by: Merative, Micromedex®

US Brand Name

1. Famvir

Descriptions

Famciclovir is used to treat the symptoms of herpes zoster (also known as shingles), a herpes virus infection of the skin. It is used to treat and suppress herpes labialis (cold sores) and recurrent episodes of genital herpes infection. This medicine is also used to treat recurrent herpes virus infections of the mucous membranes (lips and mouth) and genitals in HIV-infected patients. Although famciclovir will not cure genital herpes or herpes zoster, it does help relieve the pain and discomfort and helps the sores heal faster.

This medicine is available only with your doctor's prescription.

This product is available in the following dosage forms:

• Tablet

Before Using

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

No information is available on the relationship of age to the effects of famciclovir in children under 18 years of age. Safety and efficacy have not been established.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of famciclovir in the elderly. However, elderly patients are more likely to have age-related kidney disease, which may require an adjustment of dose in patients receiving this medicine.

Breastfeeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Galactose intolerance or
• Glucose-galactose malabsorption or
• Severe lactase deficiency—Should not use in patients with these conditions.

• Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

Proper Use

Famciclovir is best used within 48 hours after the symptoms of shingles (for example, pain, burning, blisters) begin to appear, or within 6 hours after the symptoms of recurrent genital herpes (for example, pain, blisters) begin to appear.

Famciclovir may be taken with or without food.

To help clear up your herpes infection, keep taking famciclovir for the full time of treatment, even if your symptoms begin to clear up after a few days. Do not miss any doses and do not use this medicine more often or for a longer time than your doctor ordered.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For oral dosage form (tablets):
  • For treatment of shingles:
    • Adults—500 milligrams (mg) every eight hours for seven days.
    • Children—Use and dose must be determined by your doctor.
  • For suppression of recurrent genital herpes:
    • Adults—250 milligrams (mg) two times a day for up to one year.
    • Children—Use and dose must be determined by your doctor.
  • For treatment of recurrent genital herpes:
    • Adults—1000 milligrams (mg) two times a day for one day.
    • Children—Use and dose must be determined by your doctor.
  • For treatment of recurrent herpes labialis (cold sores):
    • Adults—1500 milligrams (mg) as a single dose.
    • Children—Use and dose must be determined by your doctor.
  • For treatment of recurrent herpes infections in HIV-infected patients:
    • Adults—500 milligrams (mg) two times a day for seven days.
    • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Precautions

If your symptoms do not improve within a few days, or if they become worse, check with your doctor.

The areas affected by herpes should be kept as clean and dry as possible. Also, wear loose-fitting clothing to avoid irritating the sores (blisters).

This medicine may cause some people to become dizzy, drowsy, or less alert than they are normally. If any of these side effects occur, do not drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert while you are taking famciclovir.

This medicine does not prevent the sexual transmission of genital herpes. You should avoid having sex when lesions are present to avoid infecting your partner.

Side Effects

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:

Incidence not known

1. Black, tarry stools
2. bleeding gums
3. blistering, peeling, or loosening of the skin
4. blood in urine or stools
5. chills
6. clay-colored stools
7. cough
8. dark urine
9. dizziness
10. fever
11. joint or muscle pain
12. loss of appetite
13. pinpoint red spots on the skin
14. red, irritated eyes
15. sore throat
16. sores, ulcers, or white spots in the mouth or on the lips
17. unpleasant breath odor
18. unusual bleeding or bruising
19. vomiting of blood
20. 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:

More common

1. Cramps
2. diarrhea
3. headache
4. heavy bleeding
5. nausea
6. stomach pain

Less common

1. Bloated, full feeling
2. burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feeling
3. confusion as to time, place, or person
4. excess air or gas in the stomach or intestines
5. hives or welts
6. holding false beliefs that cannot be changed by fact
7. itching skin
8. mood or mental changes
9. passing gas
10. rash
11. redness of skin
12. seeing, hearing, or feeling things that are not there
13. unusual excitement, nervousness, or restlessness
14. unusual tiredness or weakness
15. vomiting

Incidence not known

1. 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.

Portions of this document last updated: Feb. 01, 2024

Original article: https://www.mayoclinic.org/drugs-supplements/famciclovir-oral-route/precautions/DRG-20063776