Zovirax (Aciclovir)

​​Zovirax belongs to the group of medicines called antivirals. These type of medicines attack the virus in your body to prevent it from growing and spreading, they do not kill the virus completely. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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​​​The herpes virus is the cause of several different health issues in its various forms, from the herpes simplex virus which causes cold sores and genital herpes to the varicella-zoster virus which causes chicken pox and shingles. While you can purchase an over the counter remedy to treat cold sores, sometimes this kind of treatment is simply not strong enough to combat the virus and rid you of symptoms, and it is unlikely to be strong enough to treat the other illnesses caused by the virus. In fact, the herpes virus can lay dormant in your body and reappear at any moment so when it comes to tackling illnesses caused by the herpes virus an antiviral medicine is usually required.​​ 

What is ​​Zovirax acyclovir​​? 

​​Zovirax belongs to the group of medicines called antivirals. These type of medicines attack the virus in your body to prevent it from growing and spreading, they do not kill the virus completely.  

​Zovirax acyclovir tablets contain the active ingredient acyclovir, they also contain microcrystalline cellulose, aluminium, magnesium silicate, sodium starch glycolate, povidone K30, magnesium stearate, hypromellose, polyethylene glycol 400, titanium dioxide (E171) and polyethylene glycol 8000. 

​The treatment is also available in different forms to treat different conditions. The mildest version is a topical cream or ointment.  

​The stronger medication is available as a dispersible tablet or as a liquid suspension and this is used when local topical treatments are ineffective or simply unsuitable to treat the virus. ​ 

When is ​​Zovirax acyclovir​​ used? 

​​Zovirax acyclovir is used to treat two common viral illnesses, the herpes simplex virus and the varicella-zoster virus. 

​It works by attacking the virus to prevent it from multiplying, which in turn lessens the severity of the virus to prevent it from spreading further. It is used to treat the following common illnesses:​ 

  • ​​chickenpox​ 
  • ​​shingles​ 
  • ​​cold sores 
  • ​genital herpes​ 
  • ​​hepatic whitlow 

​​ Zovirax can be used by both adults and children. 

How do you use ​​Zovirax acyclovir​​? 

​​You should always use medicines exactly as your doctor or pharmacist has instructed you to. 

​Zovirax can come as a topical cream or ointment or as a dispersible tablet. The tablet form is used to treat more severe cases and to treat chickenpox and shingles. 

​Zovirax acyclovir can also be given via intravenous drip in a hospital setting if required. 

​When taking Zovirax in tablet form at home:​ 

  • ​​Start taking your medicine as soon as possible once it has been prescribed;​ 
  • ​​Dissolve the tablet in a glass of water and stir it, then drink it;​ 
  • ​​You can also swallow the tablet whole with a little water; 
  • ​Always drink plenty of water when taking Zovirax tablets as it can cause kidney problems if you don’t.​ 

To apply the cream: 

  • Wash your hands; 
  • Apply to the affected area; 
  • Wash hands again; 
  • Repeat every four hours. 

What dosages are there? 

​​The dose you are given will depend on the severity of your virus, your age and your weight so the details below are given as a general guide only. Always take the dose that your doctor prescribes. Zovirax tablets come in a variety of sizes:​ 

  • ​​200mg​ 
  • ​​400mg 
  • ​800mg​ 


  • The usual dose is 200-800mg taken five times a day; 
  • You should space the dose so you take one tablet roughly every four hours; 
  • A suggested guide for timings is: 7 am, 11 am, 3 pm, 7 pm and 11 pm; 
  • The treatment should be taken for seven consecutive days. 

You should always complete the course of treatment given to you, even if you feel better before the treatment finishes, this is to prevent the virus from spreading again. 

Never take more than your prescribed dose. If you miss a dose take it as soon as you remember unless it is nearly time for your next dose in which case you should skip the forgotten dose.  

Never take a double dose to make up for a missed dose. Try setting an alarm as a reminder for you to take your medication at the right time. 

If you take too much Zovirax acyclovir you may experience the following: 

  • hallucinations 
  • feeling confused or agitated 
  • fits 
  • unconsciousness 

You should stop taking the medication and seek immediate medical assistance. 

Zovirax cream contains 5% acyclovir and comes in 2mg or 10mg tubes, it should be applied to the affected area every four hours. 

What are the side effects of Zovirax acyclovir? 

As with all medication, Zovirax comes with a warning of some side effects, not everyone who takes Zovirax will suffer from them. If side effects become serious or unbearable speak to your doctor. 

Zovirax comes with a risk of allergic reactions. If you experience an allergic reaction stop taking the medicine and seek immediate medical assistance. 

Signs of an allergic reaction: 

  • swelling around the face, lips or tongue 
  • a rash, itching or hives on your skin 
  • difficulty breathing, shortness of breath or wheezing 
  • unexplained high temperature 

Common side effects that may affect up to 1 in 10 people include: 

  • dizziness 
  • nausea 
  • diarrhoea 
  • stomach pain 
  • headaches 
  • itching 
  • skin reactions after exposure to light 
  • tiredness 
  • fever 

Uncommon side effects that may affect up to 1 in 100 people include: 

  • a bumpy, itchy rash like hives 
  • hair loss 
  • reduced numbers of red blood cells (anaemia) 
  • reduced numbers of white blood cells (leukopenia) 
  • reduced numbers of blood platelets – cells that help the blood to clot (thrombocytopenia) 

There are some simple things you can do try and help with the side effects like drinking plenty of water, eating a simple diet and getting plenty of rest to allow your body to recover. You can also use unscented cream to help with itching and flaking skin. 

Very rare side effects that may affect up to 1 in 10,000 people include: 

  • shaking or tremors 
  • hallucinations 
  • nosebleeds 
  • bruising easily 
  • feeling agitated or confused 
  • inability to think clearly or concentrate 
  • inflammation of the liver (hepatitis) 
  • yellowing of the skin or whites of the eyes 
  • kidney problems – passing little or no urine 
  • decreased energy, weakness, shortness of breath, light-headedness, palpitations, anaemia 
  • effects on some blood urine tests 
  • unsteadiness and lack of coordination 
  • difficulty speaking or hoarseness 
  • seizures 
  • pain in the lower back, around the kidneys or just above the hip 
  • unconsciousness 
  • paralysis of all or part of your body 

When shouldn’t you use Zovirax acyclovir? 

Do not use Zovirax if you are allergic to acyclovir, valaciclovir or any of the other ingredients listed on the packet. 

You should check with your doctor or pharmacist before taking Zovirax if any of the following apply to you: 

  • You are over the age of 65; 
  • You have a weak immune system; 
  • You have kidney problems; 
  • You are thirsty. When taking Zovirax you must ensure you are drinking plenty of liquids like water. 

Take care when driving or operating heavy machinery while taking Zovirax as you may experience dizziness, tiredness and lack of concentration. If you do experience these side effects do not drive or operate heavy machinery until you are sure they have disappeared. 

Check with your doctor or pharmacist if you are pregnant or breastfeeding as it may not be suitable for you to take Zovirax at this time. 

Does Zovirax acyclovir interact with other medications? 

As with all medication, there is a risk that different medications can interact with one another and lessen the effectiveness or cause further problems. Always discuss any medication you are taking with your pharmacist or doctor this includes herbal medicines and supplements. 

In particular, tell your doctor or pharmacist if you are taking any of the following medication: 

  • Cimetidine – which is used to treat stomach ulcers; 
  • Probenecid – which is used to treat gout; 
  • Tacrolimus, ciclosporin or mycophenolate mofetil – which are used to stop your body rejecting transplanted organs; 
  • Aminophylline or theophylline – which are used to treat asthma. 

Where can you buy Zovirax acyclovir? 

You can buy Zovirax acyclovir from any pharmacy, wherever is most convenient for you, you can purchase it online and have it delivered to your home, office or local pharmacy or you can buy it from your local pharmacy. 

Can I get Zovirax acyclovir without a prescription? 

In tablet or liquid form you can only buy Zovirax acyclovir with a prescription from a doctor. You will need to consult a doctor to check that the medication is suitable and the best option for you. 

Topical Zovirax cream to treat oral cold sores can be purchased from a pharmacy without a prescription. 


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GlaxoSmithKline (2015). Zovirax IV 250mg - Patient Information Leaflet (PIL) - (emc). [online] Medicines.org.uk. Available at: https://www.medicines.org.uk/emc/product/5472/pil [Accessed 5 Jan. 2020]. 

Herpes Viruses Association (2020). About herpes simplex virus - Herpes Viruses Association. [online] Herpes Viruses Association. Available at: https://herpes.org.uk/frequently-asked-questions/herpes-simplex-virus/ [Accessed 3 Jan. 2020]. 

NHS UK (2019). Aciclovir: a medicine used to treat cold sores, herpes and other viral infections. [online] nhs.uk. Available at: https://www.nhs.uk/medicines/aciclovir/ [Accessed 6 Jan. 2020]. 

Sinha, S. (2019). Zovirax (acyclovir) Uses, Dosage, Side Effects - Drugs.com. [online] Drugs.com. Available at: https://www.drugs.com/zovirax.html [Access0ed 3 Jan. 2020]. 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.