What aciclovir is for
Aciclovir is used to treat infections such as:
- cold sores
- shingles
- chickenpox
- genital herpes
- herpes simplex eye infections
It's also sometimes used to prevent these infections in people with a weakened immune system.
How to use aciclovir
There are several different types of aciclovir, including:
- tablets
- cream
- eye ointment
How you use your medicine and how much to use depends on which type it is and how much aciclovir it contains.
Always check the packet or leaflet that comes with your medicine. Ask a pharmacist or doctor for advice if you're not sure how to use it or have any problems using it.
If a doctor prescribes aciclovir for you, follow the advice they give you about how to use it and how much to use.
How to use common types of aciclovir
If you miss a dose of aciclovir
If you forget to take a dose of aciclovir tablets, cream or ointment, take it as soon as you remember, unless it's nearly time for your next dose.
If it's nearly time for your next dose, skip the dose you missed and take your next dose at the usual time.
Do not take 2 doses at the same time to make up for a missed one.
If you take too much aciclovir
It's unlikely that using too much aciclovir cream or ointment will be harmful, but speak to a pharmacist if you’re concerned.
Taking an extra aciclovir tablet is also unlikely to cause problems, but it's important to get medical advice if you take too much because it can sometimes be dangerous.
Urgent advice: Get help from NHS 111 if:
- you or your child has taken more than the prescribed dose of aciclovir tablets and you (or they) have symptoms such as nausea and vomiting
You can call 111 or get help from 111 online.
If you're told to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.
Bring the aciclovir packet or leaflet inside it, any remaining medicine, and any other medicines you take.
Side effects of aciclovir
Like all medicines, aciclovir can cause side effects, but not everyone gets them.
Common side effects
Common side effects of aciclovir tablets include:
- headache
- feeling dizzy or faint (particularly after standing up)
- feeling sick (nausea) or being sick (vomiting)
- diarrhoea
- stomach ache
- a rash
- a skin reaction after exposure to light
- itching
- feeling tired
- a high temperature
If you feel dizzy or faint after taking aciclovir tablets, do not drive, ride a bike or use machinery until you no longer have these symptoms.
You're less likely to get side effects from aciclovir cream or ointment. Some people get mild burning or stinging after using them, but it usually goes away quickly.
Non-urgent advice: Speak to a pharmacist or doctor if:
- you have any side effects that bother you or do not go away
They may be able to give you advice about how to reduce any side effects. Keep using your medicine unless you're advised to stop.
Serious side effects
Aciclovir tablets can sometimes cause serious side effects, although most of them are rare.
Possible serious side effects of aciclovir include:
- an allergic reaction (anaphylaxis) – causing symptoms such as a swollen throat or tongue, a raised, itchy rash and difficulty breathing
- problems with your liver – causing symptoms such as tiredness, itchy skin and yellowing of the whites of the eyes (jaundice)
- problems with your kidneys – causing symptoms such as not peeing or only being able to pee a small amount
- changes with your blood cells – causing symptoms such as tiredness, bruising easily and getting ill a lot
Urgent advice: Call NHS 111 if:
- you're using (or have recently used) aciclovir and you think you might be having serious side effects
More about side effects
These are not all the side effects of aciclovir.
For a full list, see the leaflet that came with your medicine or search for your medicine leaflet on the electronic medicines compendium website.
You can report any side effects you get on the Yellow Card Scheme website
Who can and cannot use aciclovir
Most adults can use aciclovir.
Children can usually use the cream or ointment. They may also be prescribed the tablets to treat chickenpox and shingles.
But aciclovir is not suitable for everyone. For example, you may not be able to use it if you've had an allergic reaction to aciclovir or a similar medicine called valaciclovir in the past.
Before taking aciclovir, tell your doctor if you have any medical conditions.
Breastfeeding and aciclovir
You can usually use aciclovir cream or ointment while breastfeeding, but make sure your baby does not come into contact with the areas where you've used it.
Tell your doctor if you're breastfeeding before taking aciclovir tablets.
It's rare for breastfed babies to get any side effects from medicine you're taking, but speak to a healthcare professional or call NHS 111 if you have any concerns about your baby.
Pregnancy and aciclovir
You can usually use aciclovir if you're pregnant, but check with a pharmacist or doctor first.
Using aciclovir with other medicines, food and drink
No medicines are known to affect aciclovir cream or eye ointment.
But there are certain medicines that may not mix well with some types of aciclovir tablets.
These include:
- probenecid (a medicine used to treat gout)
- cimetidine (a medicine used to treat stomach ulcers)
- mycophenolate mofetil (a medicine you may need to take after having an organ transplant)
Tell your doctor or a pharmacist if you're taking these medicines, or if you're taking any other medicines or herbal remedies bought from a shop or pharmacy.
Food, drink and alcohol with aciclovir
You can eat and drink as normal while taking aciclovir, including drinking alcohol.
It's important to drink plenty of water while taking aciclovir tablets, particularly if you have kidney problems.
Find out more about your medicine
To find out more about your medicine, you can:
- check the leaflet that comes with it
- search for your medicine leaflet on the electronic medicines compendium website
- speak to a pharmacist or doctor for advice