Class Name(s):

• 28:12.20 Succinimides

Pronunciation:

• (meth sux' i mide)

Brand Name(s):

• Celontin^®

WHY is this medicine prescribed?

Methsuximide is used to control absence seizures (petit mal; a type of seizure in which there is a very short loss of awareness during which the person may stare straight ahead or blink his eyes and does not respond to others) that cannot be treated with other medications. Methsuximide is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in the brain.

HOW should this medicine be used?

Methsuximide comes as a capsule to take by mouth. It is usually taken one or more times a day. Take methsuximide at around the same time(s) every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take methsuximide exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of methsuximide and gradually increase your dose, not more often than once a week.

Methsuximide may help control your condition but will not cure it. Continue to take methsuximide even if you feel well. Do not stop taking methsuximide without talking to your doctor, even if you experience side effects such as unusual changes in behavior or mood. If you suddenly stop taking methsuximide, your seizures may worsen. Your doctor will probably decrease your dose gradually.

Are there OTHER USES for this medication?

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before taking methsuximide,

• tell your doctor and pharmacist if you are allergic to methsuximide, ethosuximide (Zarontin), or any other medications.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while taking methsuximide. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had mental illness or kidney or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking methsuximide, call your doctor.
• if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking methsuximide.
• you should know that this medication may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
• talk to your doctor about the safe use of alcohol while you are taking this medication.
• you should know that your mental health may change in unexpected ways and you may become suicidal (thinking about harming or killing yourself or planning or trying to do so) while you are taking methsuximide. A small number of adults and children 5 years of age and older (about 1 in 500 people) who took anticonvulsants such as methsuximide to treat various conditions during clinical studies became suicidal during their treatment. Some of these people developed suicidal thoughts and behavior as early as one week after they started taking the medication. There is a risk that you may experience changes in your mental health if you take an anticonvulsant medication such as methsuximide, but there may also be a risk that you will experience changes in your mental health if your condition is not treated. You and your doctor will decide whether the risks of taking an anticonvulsant medication are greater than the risks of not taking the medication. You, your family, or your caregiver should call your doctor right away if you experience any of the following symptoms: panic attacks; agitation or restlessness; new or worsening irritability, anxiety, or depression; acting on dangerous impulses; difficulty falling or staying asleep; aggressive, angry, or violent behavior; mania (frenzied, abnormally excited mood); talking or thinking about wanting to hurt yourself or to end your life; withdrawing from friends and family; preoccupation with death and dying; giving away prized possessions; or any other unusual changes in behavior or mood. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.

What SPECIAL DIETARY instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Methsuximide may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea
• vomiting
• constipation
• diarrhea
• stomach pain
• loss of appetite
• weight loss
• hiccups
• headache
• drowsiness
• dizziness
• difficulty coordinating movements
• confusion
• slowed thinking
• unreasonable fear of developing a serious illness
• swollen eyelids
• blurred vision
• sensitivity to light

If you experience any of the following symptoms, call your doctor immediately:

• sore throat, fever, chills, and other signs of infection
• joint pain or swelling
• muscle pain
• red, itchy rash, especially on the face
• fever with no known cause
• hives
• blisters

Methsuximide may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature, away from light, excess heat, and moisture (not in the bathroom).

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://goo.gl/c4Rm4p for more information.

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach. http://www.upandaway.org

What OTHER INFORMATION should I know?

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to methsuximide.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: April 15, 2017.