Favic - Uses | Dosage | Interactions

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Favic is a drug containing an active substance called famciclovir, which is chemically known as the synthetic derivative of acyclic guanine. After oral administration, famciclovir is metabolized to penciclovir (antiviral agent), so the concentration of famciclovir in the blood is insignificant. Favic is excreted in the form of penciclovir via the kidney.


It is used for:

  • Treatment of herpes zoster infection (mainly in patients aged 18-50 years).
  • Treatment and suppression of recurrent genital herpes.
  • Treatment of herpes labialis therapy in patients in whom the immune system is not compromised.
  • Treatment and suppression of recurrent herpes simplex infections.

According to the FDA, famciclovir is also used for the treatment of recurrent orolabial and genital herpes in patients suffering from HIV infection.

Efficacy of Favic has not been established in patients who started this drug after 48 hours of symptoms onset.


The only contraindication is a known allergic reaction to famciclovir and penciclovir.

The efficacy and safety of this drug has not been established in patients:

  • Who suffer from ophthalmic herpes zoster.
  • Having the first episode of genital herpes.
  • Having compromised immune system (except for orolabial herpes and herpes zoster).
  • Under 18 years of age.

Tell your doctor if you have any of the following conditions:

  • Kidney problems. Cases of acute renal failure in patients with impaired renal function and receiving high doses of Favic have been reported. It is necessary to reduce the dose in patients whose renal function is impaired.
  • Liver problems.
  • Galactose intolerance.

Favic, pregnancy and lactation

Studies in pregnant rats and rabbits at doses that are 10.8 times higher than maximum recommended dose in humans have not shown any adverse effects on embryo-fetal development, which is why the FDA classifies this drug into category B. However, there is insufficient data on the use of this drug during human pregnancy and for this reason, the FDA recommends the use of this medication during pregnancy only when clearly needed.

There is no information whether famiciclovir or penciclovir are excreted into breast. Animal studies have shown that this drug is detected in rat milk in higher concentrations than in plasma. Favic should not be used in breastfeeding.


The recommended dosage in patients in whom the immune system is not compromised (data taken from the FDA website) is shown in the table below:

Indication Recommended dose
Treatment of herpes labialis 1500 mg as a single dose.
Treatment of recurrent episodes of genital herpes 1000 mg twice daily (just one day).
Suppressive treatment of recurrent episodes of genital herpes 250 mg twice daily.
Treatment of herpes zoster 500 mg three times daily for one week.

Note: The therapy should begin as soon as possible when the first symptoms and signs of infection occur (ideally within 48 hours of the onset of symptoms).

The recommended dose for the recurrent episode of orolabial and genital herpes in immunocompromised patients is 500 mg every 12 hours for one week.

You can take a tablet with or without food.

Always follow the dosing instructions provided by your doctor.


Favic may enter into medium interactions with the following drugs:

  • Pemetrexed (a medicine used to treat pleural mesothelioma and non-small cell lung cancer). Favic may increase the concentration of pemetrexed in the blood, thereby increasing the risk of side effects (e.g. nerve damage and bleeding). For this reason, concurrent use is not recommended.
  • Entecavir (brand names: Enteclude, Baraclude) - a medicine used to treat hepatitis C. Simultaneous administration can increase the concentration of both drugs in the blood, thereby increasing the risk of side effects of entecavir and Favic.
  • Talimogene laherparepvec (Imyglic) - a genetically modified virus that is used to treat melanoma. Favic may reduce the effectiveness of this medicine.

Favic can enter into minor interactions with the following drugs:

  • Probenecid (a medicine used to treat gout).
  • Digoxin.

Tell your doctor about all medicines and herbal preparations you are taking.

Side effects

Favic may cause the following side effects:

  • Dizziness.
  • Feeling tired.
  • Headache.
  • Drowsiness.
  • Diarrhea.
  • Stomach pain.
  • Bleeding gums.
  • Pain in the joints.
  • Loss of appetite.
  • Cramps.
  • Flatulence.
  • Mood changes.
  • Migraine.
  • Paresthesia.
  • Pancreatitis.
  • Dysmenorrhea.
  • Anemia.
  • Palpitations.
  • Confusion.

Tell your doctor if you notice any adverse effect.


  1. FDA
  2. PIL

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If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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