Ethosuximide, sold under the brand name Zarontin among others, is a medication used to treat absence seizures. It may be used by itself or with other antiseizure medications such as valproic acid. Ethosuximide is taken by mouth. Ethosuximide was approved for medical use in the United States in 1960. It is on the World Health Organization's List of Essential Medicines. Ethosuximide is available as a generic medication. As of 2019 its availability was limited in many countries with concerns of price fixing in the United States.