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Methsuximide (meth SUX i mide) has been approved by the FDA to control absence (petit mal) seizures that are not helped by other drugs.

Your epilepsy treatment should always be discussed with your healthcare provider before use. Based on their judgment and knowledge, a drug may be prescribed for other epilepsy types not included in the indications. For more information, please see the prescribing information.

How can you take methsuximide? (Available formulations)

You can take methsuximide as a capsule.

Who should not take methsuximide?

If you are allergic to methsuximide or have experienced hypersensitivity to other drugs in the succinimide class, such as ethosuximide or phensuximide, then you should not take it.

Other considerations may influence whether you should take methsuximide. Tell your healthcare provider if you:

  • have or have had liver problems.
  • have or have had kidney problems.
  • have or have had depression, mood problems, or suicidal thoughts or behavior.
  • are pregnant or plan to become pregnant.
  • are breastfeeding or plan to breastfeed.

What is important to know about taking methsuximide?

Do not stop taking methsuximide suddenly unless directed to do so by your healthcare provider.

As with all antiseizure medications, methsuximide should be withdrawn gradually to minimize the risk of causing or worsening seizures or status epilepticus. You should not stop using methsuximide suddenly unless your healthcare provider tells you to stop the medicine because of a serious side effect.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Taking methsuximide with certain other medicines may cause side effects or affect how well they work. Do not start or stop other medicines without talking to your healthcare provider. Especially tell your healthcare provider if you take: drugs that cause sleepiness or dizziness.

Women or those who are/plan to become pregnant
Use in pregnancy

At this time, there is not enough evidence regarding developmental risks associated with the use of methsuximide in pregnant people. In animal studies, there were instances of developmental issues at clinically relevant doses. However, having a seizure during pregnancy could harm both the pregnant individual and the baby. Tell your healthcare provider right away if you become pregnant. Do not start or stop taking seizure medication during pregnancy without your healthcare provider’s advice.

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 antiseizure medicine during pregnancy. You can enroll in this registry by calling 1-888-233-2334.

Use during breastfeeding

It is not known if methsuximide is present in breast milk, if there are effects on the breastfed infant, or if methsuximide impacts milk production. Talk to your healthcare provider about the risks. Your healthcare provider will consider the developmental and health benefits of breastfeeding along with your need for methsuximide and the potential effect on the infant from methsuximide or from your epilepsy.

What are the side effects of methsuximide?

Methsuximide is approved by the FDA because it is safe and effective for the majority of people who take it. However, there are risks associated with all medicines. Some side effects caused by methsuximide can be very serious, and even life-threatening. It is important to be informed about these serious reactions and to be aware of their symptoms.

Common side effects

The most common side effects that were reported in studies of methsuximide are drowsiness, dizziness, headache, blurred vision, nausea or vomiting, constipation, diarrhea, weight loss, problems with walking and coordination (unsteadiness), stomach pain, and loss of appetite.

Rare, but serious side effects
Blood dyscrasias

Blood dyscrasias, which are serious conditions in which the numbers of blood cells are lower than they should be, have been reported with the use of succinimides such as methsuximide. As a result, taking methsuximide can weaken your immune system. Your blood may need to be tested often to monitor levels of blood cells. Serious and sometimes fatal infections may occur during treatment with methsuximide. Call your healthcare provider right away if you have signs of infection such as:

  • fever
  • swollen glands, sore throat
  • easy bruising, unusual bleeding (nose, gums)
  • feeling very weak or tired
  • red or purple spots on your body
Effects on liver

Succinimides have caused changes in animal liver tissue and function during studies. For this reason, patients with known liver or renal disease will need to be cautious when taking methsuximide. Be sure to tell your healthcare provider if you have renal or liver disease. Periodic urinalysis and liver function studies are advised for all patients receiving the drug.

Systemic lupus erythematosus

Cases of systemic lupus erythematosus, a chronic inflammatory autoimmune disease, have been reported with the use of succinimides. Tell your healthcare provider right away if you experience:

  • joint pain and swelling
  • muscle pain
  • fatigue
  • low-grade fever
  • pain in the chest that is worse with breathing
  • unexplained skin rash
Suicidal thoughts or behaviors

Studies have found that people who take antiseizure medications including methsuximide may have suicidal thoughts or behaviors, which occur in approximately 1 in 500 patients. If you experience any thoughts or impulses to hurt yourself, you should contact your healthcare provider immediately.