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Generic name: methsuximidemeth-SUX-i-mide ]
Drug class: Succinimide anticonvulsants

Medically reviewed by on Jul 24, 2023. Written by Cerner Multum.

What is Celontin?

Celontin is an anti-epileptic medication, also called an anticonvulsant.

Celontin is used alone or in combination with other medications to treat absence seizures (also called "petit mal" seizures) in adults and children.

Celontin may also be used for purposes not listed in this medication guide.

Celontin side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), depressed, or have thoughts about suicide or hurting yourself.

Serious and sometimes fatal infections may occur during treatment with Celontin. Call your doctor right away if you have signs of infection such as:

  • fever;

  • swollen glands, sore throat;

  • easy bruising, unusual bleeding (nose, mouth); or

  • feeling very weak or tired.

Also call your doctor at once if you have:

  • confusion, hallucinations, unusual thoughts or behavior, extreme fear;

  • worsening seizures;

  • lupus-like syndrome--joint pain or swelling with fever, swollen glands, muscle aches, chest pain, vomiting, unusual thoughts or behavior, and patchy skin color; or

  • severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common side effects of Celontin may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Serious and sometimes fatal infections may occur during treatment with Celontin. Call your doctor right away if you have signs of infection such as: fever, swollen glands, sore throat, easy bruising, unusual bleeding (nose, mouth), feeling very weak or tired.

Do not stop using Celontin suddenly. Stopping suddenly may cause increased seizures.

Before taking this medicine

You should not use Celontin if you are allergic to Celontin or to other seizure medications.

To make sure Celontin is safe for you, tell your doctor if you have:

  • lupus;

  • liver disease;

  • kidney disease; or

  • a history of depression, mood problems, or suicidal thoughts or actions.

Some people have thoughts about suicide when taking an anticonvulsant. Your doctor should check your progress at regular visits. Your family or other caregivers should also be alert to changes in your mood or symptoms.

Follow your doctor's instructions about taking seizure medication if you are pregnant. Do not start or stop taking this medicine without your doctor's advice, and tell your doctor right away if you become pregnant. Celontin may cause harm to an unborn baby, but having a seizure during pregnancy could harm both mother and baby. The benefit of preventing seizures may outweigh any risks to the baby.

If you are pregnant, your name may be listed on a pregnancy registry. This is to track the outcome of the pregnancy and to evaluate any effects of methsuximide on the baby.

It is not known whether methsuximide passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

How should I take Celontin?

Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Celontin can weaken your immune system. Your blood may need to be tested often.

Do not stop using Celontin suddenly, even if you feel fine. Stopping suddenly may cause increased seizures. Follow your doctor's instructions about tapering your dose.

Call your doctor if your seizures get worse or you have them more often while taking Celontin.

Wear a medical alert tag or carry an ID card stating that you take Celontin. Any medical care provider who treats you should know that you take seizure medication.

Use Celontin regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

Store at room temperature away from moisture and heat. Do not allow liquid medicine to freeze.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, vomiting, extreme drowsiness, and weak or shallow breathing.

What should I avoid while taking Celontin?

Drinking alcohol with Celontin can cause side effects.

This medication may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Avoid being near people who are sick or have infections. Tell your doctor at once if you develop signs of infection.

What other drugs will affect Celontin?

Taking this medicine with other drugs that make you dizzy or sleepy can worsen this effect. Ask your doctor before taking Celontin with a sleeping pill, narcotic pain medicine, muscle relaxer, or medicine for anxiety, depression, or seizures.

Tell your doctor about all your current seizure medications, and any you start or stop using.

Other drugs may interact with methsuximide, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.