Zovirax 400

Tablet · GSK
PRESCRIPTION MEDICINE

Zovirax 400 is a tablet made by GSK that contains Acyclovir 400 mg. Acyclovir is a antiviral: treats cold sores, genital herpes, chickenpox and shingles.

Ingredient (salt)Amount
Acyclovir (aciclovir)400 mg

What it is used for

Treats cold sores, genital herpes, chickenpox and shingles.

How it works

An antiviral that stops herpes viruses copying; used for cold sores, genital herpes, chickenpox and shingles.

How to take it

Tablets: usually 200 to 800 mg up to five times a day for 5 to 7 days, started as early as possible. Cream: 5 times a day at the first tingle. Drink plenty of water.

Common side effects

  • Nausea
  • Headache
  • Diarrhoea
  • Stinging with cream

Get medical help straight away if

  • Confusion or much less urine (kidneys, mainly with high doses)
  • Severe rash

Be careful

Start early for best effect; drink plenty of water.

Other medicines and interactions

Kidney risk with other kidney-affecting medicines; dose reduced in kidney disease.

Pregnancy and breastfeeding

Considered safe in pregnancy and breastfeeding when needed.

Same composition, other brands (1)

Acivir 400

Ask your doctor or pharmacist before switching brands.

Common questions

What is Zovirax 400?

Zovirax 400 is a tablet by GSK containing Acyclovir 400 mg.

What is Zovirax 400 used for?

Treats cold sores, genital herpes, chickenpox and shingles.

How should I take Zovirax 400?

Tablets: usually 200 to 800 mg up to five times a day for 5 to 7 days, started as early as possible. Cream: 5 times a day at the first tingle. Drink plenty of water. Always follow the dose your doctor or the pack gives.

What are the side effects of Zovirax 400?

Common side effects include: Nausea, headache, diarrhoea, stinging with cream. Get medical help straight away for: Confusion or much less urine (kidneys, mainly with high doses), severe rash.

Does Zovirax 400 need a prescription?

Yes. In India it is a prescription (Schedule H) medicine, so a pharmacist should sell it only with a doctor's prescription.

Can I take Zovirax 400 in pregnancy or while breastfeeding?

Considered safe in pregnancy and breastfeeding when needed.

What are the substitutes for Zovirax 400?

Brands with the same composition: Acivir 400. Ask your doctor or pharmacist before switching.

Sources and further reading

NHS (UK National Health Service) and MedlinePlus (US National Library of Medicine) are free, reviewed medicine guides. Brand names and doses there may differ from India.

Composition checked against pack details from large Indian online pharmacies. Last reviewed 31 October 2026. Written by Satya Babu.

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For information only, not medical advice. This page is a plain-language summary written from standard prescribing information and the public guides linked below. Brands sometimes change their formula, so always check the composition printed on the pack. Doses here are typical adult doses; yours may differ. Do not start, stop or change a medicine without your doctor or pharmacist, and keep all medicines away from children. In an emergency, call 112 (India) or your local emergency number.