Ezovir - Precautions | Dosage | Effects

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

Ezovir is a medicine that contains famciclovir as an active substance. It belongs to a group of antiviral drugs used to treat infections caused by various types of herpes virus, including:

  • Herpes simplex virus type 1
  • Herpes simplex virus type 2
  • Herpes zoster virus

Studies have shown that Ezovir is rapidly biotransformed into the active metabolite called penciclovir. Penciclovir is subject to phosphorylation and is transferred into penciclovir-triphosphate that acts inhibitory on herpes virus DNA polymerase. Inhibition of DNA polymerase leads to inhibition of herpes virus reproduction, thus preventing the spread of the infection.

Therefore, Ezovir is used only to alleviate the symptoms of infections caused by herpes viruses, but does not cure herpes or prevent the recurrence of infection.

It is effective in alleviating the symptoms of herpes labialis (cold sores), herpes zoster, and recurrent episodes of genital herpes.


Since largest part of the drug is excreted unchanged (in the form of penciclovir triphosphate) via the kidneys, patients with impaired renal function must cautiously use this medicine (dose adjustment is recommended). Cases of acute renal insufficiency in patients using high doses of this drug have been reported.

It is not recommended to use this medicine:

  • In patients under the age of 18.
  • In patients with the first episode of genital herpes
  • Black and African American patients who have a recurrent episode of genital herpes.
  • In patients with ophthalmic herpes zoster.

Safety of the Ezovir in these patients has not been established.

Keep in mind that even you're treating your herpes with Ezovir, you can still spread the virus to other people. Avoid contact with other people due to an increased risk of transmission of the herpes virus.

It must be very carefully administered to patients with liver damage.

Ezovir, Pregnancy and Breastfeeding

FDA pregnancy category: B.

Studies in rats that tested doses 2.7 to 10.8 times higher than the maximum recommended doses in humans have not shown the harmful effects of Ezovir on embryo-fetal development. However, due to the lack of well-controlled clinical trials in humans, this medication should be avoided during pregnancy unless its use is clearly necessary.

It is not recommended to use Ezovir during breastfeeding since there is no information whether this medicine is excreted in breast milk or not.


The recommended dosage according to the FDA is given in the table below:

Indication Dose
Recurrent herpes labialis 1500 mg as a single dose.
Recurrent genital herpes 1000 mg twice daily for just one day.
Chronic suppressive therapy of recurrent genital herpes 250 mg twice daily.
Herpes zoster infection 500 mg three times daily for 7 days.
Herpes labialis and genital herpes in adult patients infected with HIV 500 mg twice daily for 7 days.

It is recommended to start therapy immediately at the first symptoms and signs of infection (blister, pain and itching).

Always consult your doctor about the dose you need to use.

You can take a tablet with or without food.


No major clinically significant interactions with other drugs have been reported. So far, only moderate interactions have been reported with following drugs:

  • Entecavir (brand name Enteclude) - medicine used to treat hepatitis B. Concomitant administration increases the concentration of both drugs in the blood which increases the risk of adverse effects.
  • Pemetrexed (medicine used to treat lung cancer). Ezovir increases the concentration of pemetrexed in the blood which increases the risk of side effects, such as: anemia and nerve damage.

Side effects

Ezovir may cause the following side effects:

  • Headache
  • Nausea
  • Flatulence
  • Abdominal pain
  • Dysmenorrhea
  • Paresthesia
  • Vomiting
  • Anemia
  • Leukopenia
  • Neutropenia
  • Thrombocytopenia
  • Dizziness
  • Somnolence
  • Pain in the joints and muscles
  • Unusual bleeding or bruising
  • Presence of blood in the stool (black stool)
  • Bleeding gums
  • Muscle cramps
  • Mood changes
  • Migraine
  • Pancreatitis
  • Dyspepsia
  • Acute renal failure
  • Allergic reactions


  1. FDA

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

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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