Famciclovir side effects

Famciclovir is well-tolerated, but there are a few side effects you should be aware of.


What is Famciclovir?

Famciclovir (Famvir) is a prescription drug used to treat herpes infections caused by the herpes zoster virus (shingles) and herpes simplex virus (cold sores and genital herpes). It is prescribed both to treat outbreaks and for long-term suppressive therapy of herpes.

Famvir is the branded version of the drug produced by Novartis Pharmaceuticals. Generic versions are widely available.

The recommended dosage of famciclovir depends on the type and severity of the infection.

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For genital herpes, 250 mg 3 times a day for 5 days is the recommended course. It’s best to take Famvir as soon as you notice the first signs of an outbreak, such as mild pain or tingling in the affected area.

To suppress genital herpes, 250 mg of famciclovir can be taken 2 times a day for a maximum of 12 months.

If you have cold sores around your mouth, you should take a single dose of 1.5 g of Famvir.

For patients diagnosed with herpes zoster, a dose of 500 mg 3 times a day for 7 days is recommended.

It’s best to follow your doctor’s advice on how to take famciclovir.


Famciclovir side effects

Famvir is generally safe, but patients may experience some or all of the following mild side effects:

  • Headaches
  • Dizziness
  • Nausea and vomiting
  • Abdominal pain
  • Skin rash
  • Tingling sensation

If you experience any of the following side effects, consult a doctor as soon as possible:

  • Severe rash
  • Fatigue
  • Hallucinations
  • Muscle aches
  • Signs of jaundice such as skin yellowing
  • Abnormal heartbeat


Serious Side Effects of Famciclovir

Although more severe side effects are rare, call emergency medical help in case you experience any of the following symptoms, as they could be signs of a serious or severe allergic reaction:

  • Swollen face, throat, hands or feet
  • Difficulty breathing or swallowing
  • Itching or burning of the skin
  • Bruising across the body and/or abnormal bleeding
  • Blisters developing across the body
  • Seizures

A study of 455 patients with genital herpes found that suppressive therapy with famciclovir over 1 year was well-tolerated. Therefore, long-term therapy with famciclovir appears to be safe, but additional clinical trials are needed.


Famciclovir interactions

The following drugs are known to interact with Famvir (famciclovir):

  • Live zoster vaccine (Zovastax)
  • Varicella virus vaccine
  • Cladribine (Leustatin, Mavenclad)
  • Entecavir (Baraclude)
  • Pemetrexed
  • Talimogene laherparepvec
  • Digitoxin
  • Probenecid (Probalan)

It’s best to avoid drinking alcohol while taking famciclovir. Alcohol can worsen the side effects of famciclovir and make you feel dizzy and nauseous.



  1. Faro S. (1998). A review of famciclovir in the management of genital herpes. Infectious diseases in obstetrics and gynecology, 6(1), 38–43.
  2. FAMVIR 250 mg Tablets - Summary of Product Characteristics (SmPC) - (emc). (2018). Retrieved November 1, 2019, from website:
  3. Saltzman, R., Jurewicz, R., & Boon, R. (1994). Safety of famciclovir in patients with herpes zoster and genital herpes. Antimicrobial agents and chemotherapy, 38(10), 2454–2457.
  4. Diaz-Mitoma, F. (1998). Oral Famciclovir for the Suppression of Recurrent Genital Herpes<SUBTITLE>A Randomized Controlled Trial</SUBTITLE>. JAMA, 280(10), 887.
  5. Drugscom. (2019). Famciclovir Drug Interactions. Retrieved November 1, 2019, from website:

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