Zonisamide

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Date: August 2025, Version 1.0

Quick read

Zonisamide can be used in pregnancy if recommended by a specialist.

What is it?

Zonisamide (Zonegran®, Desizon®) is used to treat some types of epilepsy.

Benefits

What are the benefits of taking zonisamide in pregnancy?

Zonisamide prevents seizures, which can be dangerous or life-threatening and can lead to pregnancy complications.

Risks

Are there any risks of taking zonisamide during pregnancy?

The small amount of available information on zonisamide use in pregnancy does not show that it harms the baby. More research is needed to confirm this.

As a precaution, zonisamide is only prescribed in pregnancy when there is no other safer treatment, and the benefits outweigh the possible risks. Your doctor will help you decide whether zonisamide treatment should be continued in pregnancy.

Babies exposed to zonisamide around the time of delivery might have some withdrawal symptoms after birth. These can be treated if necessary and usually pass quickly.

Some epilepsy medicines can affect folic acid levels. If you are taking zonisamide while trying to conceive and during pregnancy, your doctor will prescribe you a high dose folic acid supplement (5mg/day).

Alternatives

Are there any alternatives to taking zonisamide?

Possibly. Other medicines can be used to treat epilepsy. However, if your seizures are well-controlled with zonisamide, staying on it may be the safest option to keep you well and avoid pregnancy complications.

If you are planning a pregnancy, please speak to your GP or specialist to determine whether zonisamide is still the best medicine. If you have an unplanned pregnancy while taking zonisamide, you should be reviewed at the earliest opportunity by your GP or specialist.

No treatment

What if I prefer not to take medicines during pregnancy?

It is very important to take any medicines prescribed to treat epilepsy. Uncontrolled seizures can be serious and can lead to pregnancy complications.

Your doctor will only prescribe medicines when necessary and will be happy to talk about any concerns that you might have. 

Do not stop zonisamide without speaking to your GP or specialist.

Will I or my baby need extra monitoring?

All pregnant women in the UK will be offered a very detailed anomaly scan, usually at around 20 weeks of pregnancy, as part of their routine antenatal care. If you have taken zonisamide in the first trimester you may be offered this scan slightly earlier than usual. 

Zonisamide levels in your body might get lower during later pregnancy due to normal changes to your body. Your doctor might offer you a regular review of your symptoms to make sure the dose you are taking is still right.

Are there any risks to my baby if the father has taken zonisamide?

We do not expect any increased risk to your baby if the father takes zonisamide.

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet, please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.