Aciclovir for viral infections - Zovirax

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You can take aciclovir before or after food.

Space your doses out evenly over the day, and complete the full course.

Drink plenty of water. It is important that you don't get dehydrated.

Type of medicine An antiviral medicine
Used for Viral infections in adults and children
Also called Zovirax®
Available as Tablets, dispersible tablets, and oral liquid medicine

Aciclovir is used to treat two common viral infections - varicella-zoster and herpes simplex. The varicella-zoster virus is the cause of chickenpox and shingles. Herpes simplex viruses cause cold sores and genital herpes. Aciclovir works by preventing viruses from multiplying, and this reduces the severity of the infection and stops it from spreading. As well as treating infections, aciclovir can also be prescribed to prevent some viral infections from occurring. This is particularly the case in people who have a lowered immune system.

Although some herpes infections (for example, cold sores) can be treated with creams or ointments, more severe infections need to be treated with tablets or medicine taken by mouth. This leaflet provides information on how to take aciclovir tablets and medicine.

Information about the topical forms of aciclovir (creams and ointments) is not included in this leaflet. See the separate medicine leaflets called Aciclovir cream and Aciclovir eye ointment for more information about how to use these preparations.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking aciclovir it is important that your doctor knows:

  • If you are pregnant, trying for a baby, or breast-feeding.
  • If you have any problems with the way your kidneys work.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about aciclovir and a full list of the side-effects which you may experience from taking it.
  • Your dose will depend upon the type of your infection, so take aciclovir exactly as your doctor tells you to. Typically, doses range from 200 mg-800 mg, taken 2-5 times daily. Your doctor or pharmacist will tell you what dose is right for you, and this information will be printed on the label of the pack to remind you.
  • Space your doses out evenly during the day. You can take aciclovir before or after food.
  • Even if you feel your infection has cleared up, keep taking this medicine until the course is finished, unless you are told to stop.This is to prevent the infection from coming back. A course of treatment usually lasts for around 5-10 days. If you still feel unwell after finishing the course, go back to see your doctor.
  • If you forget to take a dose, take one as soon as you remember. Try to take the correct number of doses each day, but do not take two doses at the same time to make up for a missed dose.
  • If you have been prescribed a brand of tablet called Zovirax®, these tablets are dispersible and can be stirred into a small glass of water to make them easier to swallow. You can, however, swallow them as normal if you prefer.
  • You should drink plenty while you are on aciclovir to keep your kidneys working well. Drinking water is best, but hot drinks and non-alcoholic cold drinks are also suitable.
  • Aciclovir may cause your skin to become more sensitive to sunlight than it is usually. Avoid strong sunlight and sunbeds, and use a sun cream with a high sun protection factor until you know how your skin reacts.
  • If you have been prescribed aciclovir for genital herpes, do not have sex while you have sores or blisters. Even after these have healed, there is still a small chance that you may pass on the virus when you have sex - using a condom may reduce this chance.
  • If you are having an operation or any other medical treatment, tell the person carrying out the treatment that you are taking aciclovir.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common aciclovir side-effects - these affect less than 1 in 10 people who take this medicine
What can I do if I experience this?
Feeling or being sick, stomach ache Stick to simple foods - avoid rich or spicy meals
Itchy rash If this becomes troublesome, speak with your doctor
Headache, fever Ask your pharmacist to recommend a suitable remedy
Diarrhoea Drink plenty of water to replace any lost fluids
Feeling dizzy or tired If this happens, do not drive or use tools or machines until you feel better

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

  • Manufacturer's PIL, Zovirax® Tablets 800 mg; GlaxoSmithKline UK, The electronic Medicines Compendium. Dated November 2008.
  • British National Formulary; 65th Edition (Mar 2013) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
1401 (v25)
Last Checked:
10/09/2013
Next Review:
09/09/2016
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