This medication is used to manage and prevent certain types of seizures (those caused by absence [petit mal] epilepsy). It may be used at the same time as other medications that are used to control different types of seizures. It helps to control seizures by working on the central nervous system.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The usual starting dose of ethosuximide for children ages 3 to 6 years old is 250 mg taken by mouth, once daily. Older children and adults may be started with 500 mg daily, taken in divided doses.

The dose of ethosuximide varies according to the needs and age of the person using the medication and their response to treatment. Depending on the effectiveness of the medication and how well it is tolerated, your doctor may slowly increase the dose until a maximum effect is achieved, with minimum side effects. Often a dose of 1 g to 1.5 g daily in divided doses controls seizures in adults.

Ethosuximide may be taken with food or on an empty stomach. Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature in a dry environment. Ethosuximide capsules are sensitive to conditions of high humidity, which can result in decreased effectiveness of the medication.

Capsules
Each soluble gelatin capsule contains 250 mg of ethosuximide. Nonmedicinal ingredients: D&C Yellow No. 10, FD&C Red No. 3, gelatin, glycerin, polyethylene glycol, and sorbitol.

Syrup
Each 5 mL contains 250 mg of ethosuximide. Nonmedicinal ingredients: alcohol, citric acid anhydrous, FD&C Yellow No. 6, FD&C Red No. 3, flavouring agents, glycerin, purified water, saccharin sodium, sodium benzoate, sodium citrate, sucrose, and vanillin. Gluten-, lactose-, parabens-, sulfite-, and tartrazine-free.

Do not take this medication if you:

• are allergic to ethosuximide or any ingredients of the medication
• are allergic to any of the medications in the succinimide family (e.g., methsuximide)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• dizziness
• drowsiness
• heartburn
• hiccups
• loss of appetite
• nausea
• night terrors
• sleepiness
• stomach cramps
• stomach pain
• trouble sleeping
• vomiting
• weight loss

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• behaviour changes (e.g., aggression, irritability)
• difficulty concentrating
• enhanced feeling of well-being and happiness
• hallucinations (seeing or hearing things that aren't there)
• hyperactivity
• joint pain and inflammation
• loss of coordination of voluntary movement
• increased occurrences of cold or flu-like symptoms (e.g., sore throat, runny nose, nasal congestion)
• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• increased seizures
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of porphyria (a disease of the red blood cells; e.g., abdominal pain, light sensitivity, rashes, blistering on the skin, mental changes)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• thoughts of suicide or self-harm

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Blood disorders: Blood disorders, although infrequent, may be serious and have been reported to be associated with the use of this medication. Ethosuximide can decrease the number of neutrophils (a type of white blood cell that helps fight infection), red blood cells (which carry oxygen), and platelets (which help your blood to clot). Your doctor may do blood tests to monitor this. If you notice any signs of infection (e.g., fever, chills, or sore throat) or unusual bleeding or bruising, contact your doctor immediately.

Drowsiness/reduced alertness: Ethosuximide may impair the mental or physical abilities required for potentially dangerous activities such as driving or operating machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how this medication affects you.

Hypersensitivity reactions: Ethosuximide has occasionally caused a severe allergic reaction known as multi-organ hypersensitivity syndrome. This reaction involves a number of organs in the body and may be fatal if not treated quickly. Stop taking the medication and get immediate medical attention if you have symptoms of a severe allergic reaction, including fever, swollen glands, yellowing of the skin or eyes, or flu-like symptoms with skin rash or blistering.

Kidney function: If you have kidney problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function:  Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

People taking ethosuximide may have changes in liver function that produce abnormal liver test results. Your doctor will recommend regular liver tests while you are taking this medication.

Lupus: Cases of systemic lupus erythematosus (SLE) have been reported with the use of ethosuximide. If you have SLE, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Seizures: This medication may increase the frequency of experiencing tonic-clonic, or grand mal seizures for people that experience mixed types of seizures. If you experience an increase in the number of seizures you have, or different types of seizures, contact your doctor as soon as possible.

Suicidal behaviour: People taking this medication may feel that they want to hurt themselves or others. These symptoms may occur within several weeks after starting this medication.  If you experience these side effects or notice them in a family member who is taking this medication, contact your doctor immediately. You should be closely monitored by your doctor for emotional and behaviour changes while taking this medication.

Pregnancy: Women subject to major seizures should not stop taking this medication during pregnancy. For women subject to minor seizures, the risk of stopping the medication prior to or during pregnancy should be weighed against the risk of birth defects. If you become pregnant while taking this medication, contact your doctor right away.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking ethosuximide, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of this medication have not been established for children less than 3 years of age.

There may be an interaction between ethosuximide and any of the following:

• alcohol
• antihistamines (e.g., azelastine, bilastine, cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine, rupatadine)
• antipsychotics (e.g., cariprazine, chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• apalutamide
• barbiturates (e.g., butalbital, phenobarbital)
• benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
• bosentan
• brimonidine
• butorphanol
• cannabis
• chloral hydrate
• clonidine
• cobicistat
• dantrolene
• desipramine
• dimenhydrinate
• diphenoxylate
• efavirenz
• entacapone
• enzalutamide
• esketamine
• eszopiclone
• flibanserin
• guanfacine
• lemborexant
• mefloquine
• methadone
• metoclopramide
• mirtazapine
• mitotane
• muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
• nabilone
• narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tapentadol, tramadol)
• orlistat
• pizotifen
• pramipexole
• pregabalin
• rifampin
• ropinirole
• rotigotine
• scopolamine
• seizure medications (e.g., clobazam, carbamazepine, levetiracetam, phenobarbital, phenytoin, primidone, rufinamide, topiramate, valproic acid, zonisamide)
• tetrabenazine
• thalidomide
• tizanidine
• trazodone
• tricyclic antidepressants (e.g., clomipramine, desipramine, imipramine)
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.