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Last reviewed on RxList: 1/5/2017
Zarontin Side Effects Center

Last reviewed on RxList 12/22/2016

Zarontin (ethosuximide) is an anti-epileptic medication, also called an anticonvulsant, used alone or in combination with other medications to treat absence seizures (also called "petit mal" seizures) in adults and children. Zarontin is available in generic form. Common side effects of Zarontin include:

A small number of people who take anticonvulsants such as Zarontin may experience depression, suicidal thoughts/attempts, or other mental/mood problems. Tell your doctor immediately if you have unusual or sudden changes in your mood, thoughts, or behavior including signs of depression, suicidal thoughts or attempts, or thoughts about harming yourself.

The initial dose of Zarontin for patients 3 to 6 years of age is one capsule (250 mg) per day; for patients 6 years of age and older, 2 capsules (500 mg) per day. The dose thereafter is individualized according to patient response. Zarontin may interact with other seizure medications, especially phenobarbital or phenytoin. Other drugs may interact with Zarontin. Tell your doctor all prescription and over-the-counter medications and supplements you use. During pregnancy, Zarontin should be used only when prescribed. This medication passes into breast milk, but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.

Our Zarontin (ethosuximide) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.

Zarontin Consumer Information

Get emergency medical help if you have any of these 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, depression, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have a serious side effect such as:

  • fever, chills, swollen glands, flu symptoms, sore throat, swollen glands, feeling very weak;
  • new or worsening cough with fever, trouble breathing;
  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;
  • joint pain or swelling with mild fever, muscle aches;
  • chest pain, irregular heart rhythm, feeling short of breath;
  • patchy skin color, red spots, or a butterfly shaped skin rash over your cheeks and nose (worsens in sunlight);
  • skin rash, severe tingling, numbness, pain, muscle weakness;
  • upper stomach pain, loss of appetite, dark urine, jaundice (yellowing of the skin or eyes);
  • confusion, hallucinations, unusual thoughts or behavior, extreme fear;
  • swelling, rapid weight gain, urinating less than usual or not at all;
  • the first sign of any skin rash, no matter how mild;
  • 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; or
  • worsening of seizures.

Less serious side effects may include:

  • upset stomach, mild nausea, stomach cramps, diarrhea, weight loss;
  • swelling in your tongue or gums;
  • headache, dizziness, drowsiness, feeling tired;
  • lack of balance or coordination; or
  • unusual vaginal bleeding.

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.

Read the entire detailed patient monograph for Zarontin (Ethosuximide)

Zarontin Professional Information


Body As A Whole: Allergic reaction. Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).

Gastrointestinal System: Gastrointestinal symptoms occur frequently and include anorexia, vague gastric upset, nausea and vomiting, cramps, epigastric and abdominal pain, weight loss, and diarrhea. There have been reports of gum hypertrophy and swelling of the tongue.

Hemopoietic System: Hemopoietic complications associated with the administration of ethosuximide have included leukopenia, agranulocytosis, pancytopenia, with or without bone marrow suppression, and eosinophilia.

Nervous System: Neurologic and sensory reactions reported during therapy with ethosuximide have included drowsiness, headache, dizziness, euphoria, hiccups, irritability, hyperactivity, lethargy, fatigue, and ataxia. Psychiatric or psychological aberrations associated with ethosuximide administration have included disturbances of sleep, night terrors, inability to concentrate, and aggressiveness. These effects may be noted particularly in patients who have previously exhibited psychological abnormalities. There have been rare reports of paranoid psychosis, increased libido, and increased state of depression with overt suicidal intentions.

Integumentary System: Dermatologic manifestations which have occurred with the administration of ethosuximide have included urticaria, pruritic erythematous rashes, and hirsutism.

Special Senses: Myopia.

Genitourinary System: Vaginal bleeding, microscopic hematuria.

Read the entire FDA prescribing information for Zarontin (Ethosuximide)

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