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Methsuximide (Celontin): Uses, Side Effects and Dosage

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300 mg
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Source: FDA drug labeling via NLM DailyMed · About this document

Patient information: uses, side effects, how to take - Methsuximide

What is the most important information I should know about methsuximide?

Do not stop taking methsuximide without first talking to your healthcare provider. Stopping methsuximide suddenly can cause serious problems.

Methsuximide can cause serious side effects, including:

1. Rare but serious blood problems that may be life-threatening. Call your healthcare provider right away if you have:

  • fever, swollen glands, or sore throat that come and go or do not go away
  • frequent infections or an infection that does not go away
  • easy bruising
  • red or purple spots on your body
  • bleeding gums or nose bleeds
  • severe fatigue or weakness
  1. 2. Systematic Lupus Erythematosus. Call your healthcare provider right away if you have any of these symptoms:
  • joint pain and swelling
  • muscle pain
  • fatigue
  • low-grade fever
  • pain in the chest that is worse with breathing
  • unexplained skin rash

3. Like other antiepileptic drugs, methsuximide may cause suicidal thoughts or actions in a very small number of people, about 1 in 500.

Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you:

  • thoughts about suicide or dying
  • attempts to commit suicide
  • new or worse depression
  • new or worse anxiety
  • feeling agitated or restless
  • panic attacks
  • trouble sleeping (insomnia)
  • new or worse irritability
  • acting aggressive, being angry, or violent
  • acting on dangerous impulses
  • an extreme increase in activity and talking (mania)
  • other unusual changes in behavior or mood

How can I watch for early symptoms of suicidal thoughts and actions?

  • Pay attention to any changes, especially sudden changes, in mood, behaviors, thoughts, or feelings.
  • Keep all follow-up visits with your healthcare provider as scheduled.

Call your healthcare provider between visits as needed, especially if you are worried about symptoms.

Do not stop methsuximide without first talking to a healthcare provider. Stopping methsuximide suddenly can cause serious problems. Stopping a seizure medicine suddenly in a patient who has epilepsy can cause seizures that will not stop (status epilepticus).

Suicidal thoughts or actions can be caused by things other than medicines. If you have suicidal thoughts or actions, your healthcare provider may check for other causes.

What is methsuximide?

Methsuximide is a prescription medicine used to treat absence (petit mal) seizures that have not gotten better with other seizure medicines.

Who should not take methsuximide?

Do not take methsuximide if you are allergic to succinimides (methsuximide or ethosuximide) or any of the ingredients in methsuximide. See the end of this Medication Guide for a complete list of ingredients in methsuximide.

What should I tell my healthcare provider before taking methsuximide?

Before you take methsuximide, tell your healthcare provider if you:

  • have or have had liver problems
  • have or have had depression, mood problems or suicidal thoughts or behavior
  • have any other medical conditions

  • are pregnant or plan to become pregnant. It is not known if methsuximide can harm your unborn baby. Tell your healthcare provider right away if you become pregnant while taking methsuximide. You and your healthcare provider will decide if you should take methsuximide while you are pregnant.

    • If you become pregnant while taking methsuximide, talk to your healthcare provider about registering with the North American Antiepileptic Drug (NAAED) Pregnancy Registry. The purpose of this registry is to collect information about the safety of antiepileptic drugs during pregnancy. You can enroll in this registry by calling 1-888-233-2334.
  • are breastfeeding or plan to breastfeed. It is not known if methsuximide can pass into breast milk. You and your healthcare provider should decide how you will feed your baby while you take methsuximide.

Tell your healthcare provider about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Taking methsuximide with certain other medicines can cause side effects or affect how well they work. Do not start or stop other medicines without talking to your healthcare provider.

Know the medicines you take. Keep a list of them with you to show your healthcare provider and pharmacist each time you get a new medicine.

How should I take methsuximide?

  • Take methsuximide exactly as prescribed. Your healthcare provider will tell you how much methsuximide to take.
  • Your healthcare provider may change your dose. Do not change your dose of methsuximide without talking to your healthcare provider.
  • If you take too much methsuximide, call your healthcare provider or your local Poison Control Center right away.

What should I avoid while taking methsuximide?

  • Do not drink alcohol or take other medicines that make you sleepy or dizzy while taking methsuximide without first discussing this with your healthcare provider. Methsuximide taken with alcohol or medicines that cause sleepiness or dizziness may make your sleepiness or dizziness worse.
  • Do not drive, operate heavy machinery, or do other dangerous activities until you know how methsuximide affects you. Methsuximide can slow your thinking and motor skills.

What are the possible side effects of methsuximide?

  • See "What is the most important information I should know about methsuximide?"

Methsuximide may cause other serious side effects, including:

  • Grand mal seizures can happen more often or become worse

The most common side effects of methsuximide include:

  • drowsiness
  • dizziness
  • headache
  • blurred vision
  • nausea or vomiting
  • constipation
  • diarrhea
  • weight loss
  • problems with walking and coordination (unsteadiness)
  • stomach pain
  • loss of appetite

Tell your healthcare provider about any side effect that bothers you or that does not go away.

These are not all the possible side effects with methsuximide. For more information, ask your healthcare provider or pharmacist.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store methsuximide?

  • Store methsuximide at room temperature, between 59°F to 86°F (15°C to 30°C).
  • Keep methsuximide capsules in a dry place.
  • Keep methsuximide out of the light.
  • Protect methsuximide from heat.
  • Do not use methsuximide capsules that if they do not look full or if the contents have melted.

Keep methsuximide and all medicines out of the reach of children.

General information about methsuximide

Medicines are sometimes prescribed for purposes other than those listed in a Medication Guide. Do not use methsuximide for a condition for which it was not prescribed. Do not give methsuximide to other people, even if they have the same condition. It may harm them.

This Medication Guide summarizes the most important information about methsuximide. If you would like more information, talk with your healthcare provider. You can ask your healthcare provider or pharmacist for information about methsuximide that is written for healthcare professionals.

For more information, call 1-855-204-1431.

What are the ingredients in methsuximide?

Active ingredient: methsuximide

Inactive ingredients: corn starch, colloidal silicon dioxide and magnesium stearate. The capsule shells contain gelatin, purified water, sodium lauryl sulfate, D&C Yellow No.10 and FD&C Yellow No.6. The imprinting ink contains shellac, alcohol, isopropyl alcohol, butyl alcohol, propylene glycol, ammonia, black iron oxide, potassium hydroxide and purified water.

Trademarks are the property of their respective owners.

This Medication Guide has been approved by the U.S. Food and Drug Administration.

Distributed by:

ANI Pharmaceuticals, Inc.

Baudette, MN 56623

Issued: 11/2022

LB4557-00

About this document

Source: FDA drug labeling via NLM DailyMed · Application number: ANDA 217213 · View the label on DailyMed

Revision date stated in the text: November 2022

Found a mistake? Write to us via the contact page.

The information on this site does not replace the advice of a doctor or pharmacist.

Drug information for Methsuximide

Rx or OTC
Prescription (Rx)?
  • This drug is available only with a prescription from a licensed healthcare provider.
  • Rx
Drug class Anti-epileptic Agent
Active ingredient Methsuximide 300 mg
Dosage form Capsule
Route Oral
Marketing status listed in the FDA NDC Directory
Company (applicant) NOVITIUM PHARMA
FDA approval ANDA 217213Abbreviated New Drug Application (ANDA) – generic drug Approved May 1, 2023
Therapeutic equivalence (TE) code ABCodes starting with A mean the FDA rates the drug therapeutically equivalent to its reference drug (Orange Book).
Generics Celontin with the same TE code
Manufacturers 1 labelers list this drug on DailyMed
Packages (NDC)
Package
300 mg – 100 in 1 bottle NDC 70954-228-10

Source: FDA drug labeling via NLM DailyMed, data as of October 31, 2026. FDA data (DailyMed, Orange Book, Drug Shortages, enforcement reports). Not a substitute for the advice of a doctor or pharmacist.