Patient leaflet - Aciclovir 400 mg tablets

1. What Aciclovir is and what it is used for

Aciclovir Tablets contain the active ingredient aciclovir which is an antiviral medicine. It works by killing or stopping the growth of viruses that can cause certain infections.

These tablets are used to treat chickenpox (varicella) and shingles (herpes zoster). The 200mg and 400mg tablets are also used to:

treat or prevent cold sores and genital herpes (herpes simplex infections), and other herpes simplex infections
prevent herpes simplex infections in people whose immune systems don’t work properly
stop these problems returning after you have had them

2. What you need to know before you take Aciclovir

Do not take Aciclovir Tablets:

if you are allergic to aciclovir or valaciclovir or any of the other ingredients of this medicine (listed in section 6). Do not take Aciclovir tablet if the above applies to you. If you are not sure, talk to your doctor or pharmacist before taking Aciclovir tablet.

Warnings and precautions

Talk to your doctor or pharmacist before taking these tablets if:

if you have had severe skin reactions with aciclovir or valaciclovir
you have kidney problems.
you are over 65 years of age.

If you are not sure if the above apply to you, talk to your doctor or pharmacist before taking Aciclovir tablet. It is important to drink plenty of water whilst taking this medicine, particularly if you are elderly, have kidney problems or are taking a high dose of this medicine.

Conditions you need to look out for

Aciclovir tablet can cause severe skin reactions. You must look out for certain symptoms while you are taking Aciclovir tablet, to reduce the risk of any problems. If you experience any signs or symptoms of severe skin reactions, stop using Aciclovir tablet and contact your doctor immediately (see ‘Possible side effects’). Other medicines and Aciclovir

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. This includes medicines obtained without a prescription, including herbal medicines. In particular, tell your doctor or pharmacist if you are taking any of the following:

probenecid, used to treat gout.
cimetidine, used to treat stomach ulcers.
mycophenolate mofetil, used to stop your body rejecting transplanted organs.
theophylline, used in asthma.

Pregnancy, breast-feeding and fertility

There is limited information on the use of this medicine in pregnancy, breast-feeding and fertility. If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.

Driving and using machines

Some side effects such as drowsiness or dizziness may affect your ability to concentrate and react. Make sure you are not affected before you drive or operate machinery.

Aciclovir 200mg, 400mg, 800mg Tablets contain sodium

This medicine contains less than 1 mmol sodium (23mg) per tablet, that is to say essentially “sodium-free”.

3. How to take Aciclovir Tablets

Always take this medicine exactly as your doctor has told you. Check with your doctor or pharmacist if you are not sure. It is important to start taking these tablets as soon as possible and you should continue to take them for as long as your doctor has recommended, even if you start to feel better. Swallow the tablets whole with some water, with or without food. The score line on Aciclovir 800mg Tablets is not intended for breaking the tablets.

Drink plenty of water while you are taking this medicine.

Usual doses:

Adults – Treatment of chickenpox and shingles: Take 800mg five times a day for 7 days. Take at four hourly intervals except during the night (for example at 7am, 11am, 3pm, 7pm and 11pm). Adults - Cold sores and genital herpes (herpes simplex infection)

Treatment: Take 200mg five times a day for 5 days or longer if your doctor tells you to. Take at four hourly intervals except during the night (for example at 7am, 11am, 3pm, 7pm and 11pm). Prevention: Take 200mg four times a day, about every 6 hours. Continue taking until your doctor tells you to stop. To avoid getting these infections if your immune system isn’t working properly: Take 200mg four times a day, about every 6 hours. Continue taking until your doctor tells you to stop. Children – Treatment of Chickenpox

Children 6 years and over: 800mg four times a day for 5 days.

Children 2 to 5 years: 400mg four times a day for 5 days.

Children under 2 years: 200mg four times a day for 5 days.

Children - Cold sores and genital herpes (herpes simplex infection)

Treatment of the infection and prevention of the infection when their immune system is not working properly: Children 2 years and over: same as the adult dose.

Children under 2 years: half the adult dose.

Elderly and people with kidney problems

Your doctor may give you a lower dose than the usual doses above if you are elderly or if you have kidney problems.

If you take more Aciclovir Tablets than you should:

Product: Aciclovir 200mg, 400mg and 800mg tablets - Jingxin

Amendment Date

pharmacist if you take too many tablets. Take the medicine pack with you. Signs of overdose include feeling or being sick, headache and being confused.

If you forget to take Aciclovir Tablets:

If you forget to take a tablet, take it as soon as you remember. However, if it is nearly time for your next dose, skip the missed dose. Do not take a double dose to make up for a forgotten dose.

4. Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them. Conditions you need to look out for

Allergic reactions (may affect up to 1 in 1,000 people)

If you experience any of the following signs, stop taking these tablets and seek medical attention IMMEDIATELY as these are signs of a serious allergic reaction:

difficulty breathing or swallowing, wheezing
rash, itching or hives on your skin
swelling of your face, lips, tongue or other parts of your body
collapse

Severe skin reactions: These are very rare (these may affect up to 1 in 10,000 people) taking Aciclovir tablet. Signs include:

widespread red or scaly rash with blisters (that may contain pus), bumps under the skin or peeling of skin. Flu-like symptoms with a rash, fever, swollen glands, and abnormal blood test results. Contact a doctor immediately if you get these symptoms. Stop taking Aciclovir tablet. Tell your doctor, pharmacist or nurse if you suffer from any of the following other effects. Common (may affect up to 1 in 10 people)
tiredness
unexplained fever (high temperature)
headache, dizziness
feeling or being sick, stomach pains, diarrhoea
itching, skin rashes including reaction to light (photosensitivity)
feeling faint, especially when standing up.

Uncommon (may affect up to 1 in 100 people)

itchy, red, nettle-like rash (hives)
hair loss

Rare (may affect up to 1 in 1,000 people)

increased levels of blood urea and creatinine, and of bilirubin and liver related enzymes which will be shown in blood tests.

Very rare (may affect up to 1 in 10,000 people)

feeling agitated or confused and not being able to think or judge clearly
hallucinations (seeing or hearing things that are not there)
feeling weak, unusually sleepy or drowsy
shaking, tremors, difficulty in controlling movement and difficulty speaking
unsteadiness when walking and lack of coordination
inflammation of the liver (hepatitis) and yellowing of the skin and whites of the eyes (jaundice)
pain in the lower back (kidney pain) and kidney failure where you pass little or no urine
blood disorders (signs include pale skin, feeling unusually tired or breathless, sore throat, easier bruising, nose bleeds, getting infections more than usual)
reduced numbers of red blood cells (anaemia)
reduced numbers of white blood cells (leukopenia)
reduced numbers of blood platelets (cells that help blood to clot (thrombocytopenia)
fits (seizures)
unconsciousness (coma)
encephalopathy, a disorder affecting the brain (signs include memory loss, confusion, lack of concentration, twitching, rapid eye movement, loss of muscle strength and coordination)
paralysis of part or all of your body
disturbances of behaviour, speech and eye movements
stiff neck and sensitivity to light
severe skin reactions, such as widespread red or scaly rash with blisters (that may contain pus), bumps under the skin or peeling of skin. Flu-like symptoms with a rash, fever, swollen glands, and abnormal blood test results. (see ‘Conditions you need to look out for’).

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store Aciclovir Tablets

Keep this medicine out of the sight and reach of children.

Do not store above 30°C.

Do not use this medicine after the expiry date which is stated on the carton and on the blister after EXP. The expiry date refers to the last day of that month.

Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.

6. Contents of the pack and other information

What these tablets contain

The active ingredient is aciclovir. Each tablet contains 200mg, 400mg or 800mg of aciclovir. The other ingredients are: povidone, sodium starch glycolate type A, microcrystalline cellulose and magnesium stearate. What these tablets looks like and contents of the pack

Aciclovir 200mg Tablets are white, round, biconvex tablets with a diameter of 9mm and marked '200' on one side.

Aciclovir 400mg Tablets are white, round, biconvex tablets with a diameter of 11mm. Aciclovir 800mg Tablets are white, oval, biconvex tablets, 19.3mm long, with a score line on one side. The tablets are available in pack sizes of 25 (200mg), 56 (400mg) and 35 (800mg). Marketing Authorisation Holder:

Crescent Pharma Ltd., Key House, Sarum Hill, Basingstoke, RG21 8SR, UK. Manufacturers:

Crescent Pharma Ltd., Key House, Sarum Hill, Basingstoke, RG21 8SR, UK. Pharmaceutical Works Polpharma S.A., 19 Pelplińska Street, PL-83-200 Starogard Gdański, Poland This leaflet was last revised in March 2026.

If you require this leaflet in a different format please contact the Marketing Authorisation Holder at the address above.

Other sources of information

Detailed information on this medicine is available on the web site of Medicines Healthcare products Regulatory Agency (MHRA).

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