Ethosuximide is used to control seizures (fits).

Like all medicines, this medication may cause some possible side effects but not everyone experiences them. Consult your healthcare professional if any of the side effects lasts more than a few days or become severe and bothersome.

The common side effects of Ethosuximide include:

• Dizziness
  
  • Stand up or sit up slowly from a lying or sitting position. 
• Drowsiness
  • This may affect your ability to drive and use machinery.
  • Make sure your reactions are normal before you drive or do things that require you to be alert. 
• Loose stools (Diarrhoea)
  • Drink plenty of clear fluids to replace those lost (two liters every day). 
  • Avoid oily or spicy food and milk or daily products. 
  • You may have foods such as porridge or soups which are gentler on the stomach. 
  • Take the anti-diarrheal medication (e.g., Loperamide) that the doctor gives you when necessary
• Nausea, vomiting
  • Take the medication after food, eat small but frequent meals. 
  • Avoid fatty or spicy food.
• Headache
  • You may take paracetamol to treat the headache
• Loss of appetite, abdominal pain
• Hiccups
• Poor muscle coordination

The symptoms of a drug allergy include one or more of the following:

• Swollen face / eyes/ lips / tongue
• Difficulty in breathing
• Itchy skin rashes over your whole body

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

If the following serious side effects happen, you should consult your healthcare professional immediately:

• Blistering, peeling, red skin rash due to Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)
  • SJS and TEN are rare and serious skin reactions which can happen after using some medications. 
  • Symptoms include mouth ulcers, face swelling, blisters on skin, skin rashes that spread throughout the body within hours to days after starting the medication. 
  • This usually occurs within the first few months (monitor closely for the first 3 months) of treatment.
• Unusual bleeding and bruising
• Prolonged fever, sore throat and mouth sores
• Rash, joint swelling, swelling at neck and armpits
• Unusual movement disorders

In rare cases, this medication may cause the following changes to a person’s mental condition, especially in the first few weeks of treatment or during dose changes:

• Worsening agitation, restlessness, violent behaviour
• New or worsening thoughts of harming yourself or ending your life
• Other changes in mood or behaviour

Please inform your doctor as soon as possible, or for your family or caregiver to inform your doctor if you are unable to seek treatment on your own. 

Do not stop taking this medication on your own without discussing with your doctor. 

It is important to note that your doctor has prescribed this medication as he/ she feels you will benefit more from taking this medication over the possible side effects that it may cause, which have a low chance of occurring. Most people take this medication without any such problems.

There are certain restrictions in the supply of Ethosuximide. Ethosuximide is not available in community/retail pharmacies and is only available in selected healthcare institutions via prescription from in-house doctors. Please check with your healthcare provider if they are able to supply it. 

Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Jan 2025