Aciclovir (Zovirax eye ointment)

How does it work?

Zovirax eye ointment contains the active ingredient aciclovir, which is an antiviral medicine. Aciclovir is used to treat infections with the herpes simplex virus.

Aciclovir works by stopping the herpes simplex virus from reproducing and infecting more cells.

Aciclovir is converted to a more active form inside cells of the body that are infected with herpes simplex. The activated aciclovir then works by blocking the action of a viral enzyme called DNA polymerase.

The herpes virus needs the DNA polymerase enzyme to copy its genetic material from RNA to DNA. This process is necessary for the virus to multiply and continue to survive. By blocking the action of DNA polymerase, aciclovir prevents the herpes virus from multiplying. This controls the infection and helps the immune system to deal with it.

Zovirax eye ointment is specially formulated to treat inflammation of the front of the eye (cornea) caused by infection with the herpes simplex virus. This serious infection is called herpes simplex keratitis.

The ointment should be applied five times a day, at approximately four-hourly intervals. Treatment with this medicine should continue for at least three days after the eye has healed to ensure the infection has cleared up fully. Follow the instructions given by your doctor.

What is it used for?

  • Inflammation of the front of the eye (cornea) caused by infection with the herpes simplex virus (herpes simplex keratitis).


  • This medicine is only suitable for use in the eye.
  • Contact lenses should not be worn during treatment with this product.
  • This medicine may cause your vision to blur temporarily after you have applied it into your eye. Do not drive or operate machinery until this has worn off.
  • If you are using more than one type of eye drop you should administer them at least five minutes apart, to prevent the second drop washing away the first. Use eye gels or ointments last.
  • This eye ointment is sterile until opened. It should not be used if more than four weeks have passed since it was first opened, as it may be contaminated with germs that could infect the eye. You may find it helpful to write the date of first opening on the packet so you know when to dispose of it.

Not to be used in

  • Allergy to aciclovir or valaciclovir.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine is not known to be harmful if used during pregnancy. It is absorbed into the bloodstream only in very low amounts after being applied to the eyes. However, the manufacturer states that it should be used with caution during pregnancy, and only if the expected benefit to the mother is greater than any possible risk to the baby. If you are pregnant you should ask your doctor for advice before using this medicine.
  • This medicine is absorbed into the bloodstream only in very low amounts after being applied to the eyes. As a result, the quantities that pass into breast milk are expected to be insignificant and unlikely to have a harmful effect on a nursing infant. However, as with all medicines, you should seek medical advice from your doctor before using this medicine if you are breastfeeding.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Eye irritation.

Common (affect between 1 in 10 and 1 in 100 people)

  • Stinging on application.
  • Inflammation of the lining of the eye, causing pain and redness (conjunctivitis).

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Inflammation of the eyelids (blepharitis).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

There are no significant interactions reported with this medicine. However, if you are using other are using any other eye drops or ointments at the same time as this eye ointment, you should leave a five minute interval between the application of each product into the eye. Eye ointments should be applied into the eye last.

Other medicines containing the same active ingredient

NB. None of the medicines listed below are suitable for treating herpes infection of the eye.

Cymex ultra Lypsyl cold sore cream Soothelip
Virasorb cold sore creamZovirax cold sore creamZovirax cream
Zovirax tablets/suspension

Aciclovir cold sore cream, cream, tablets and dispersible tablets are also available as the generic medicine, ie without a brand name.