Zarontin (ethosuximide) generally is used only for the brief staring spells known as absence seizures (formerly known as "petit mal" seizures). It is highly effective and safe for children who have the disorder known as childhood absence epilepsy, which occurs in 8% of children with epilepsy between ages 5 and 14 years. This disorder usually begins between ages 4 and 8 in children without previous brain disorders. Often someone else in the family has had the same disorder in the past. The diagnosis can be confirmed by detecting a particular EEG pattern during a seizure. (The EEG is normal at other times.) The doctor almost always can cause this kind of absence seizure to occur in the office by having the child hyperventilate (breathe especially fast or deeply) for a few minutes. Although these seizures usually will stop when the child gets older, children who have them need effective treatment to avoid learning problems and accidental injuries.

Zarontin is often the first choice of medication for childhood absence epilepsy. In one early study, 95% of patients had the number of seizures reduced by at least half, and about half the patients had them reduced by at least 90%.

Some children who have absence seizures have more complicated disorders that are harder to treat and may not be outgrown, such as "atypical absence" or juvenile myoclonic epilepsy. These children may also have other types of seizures. They often are older when the absence seizures begin, and they have a different EEG pattern than children with typical childhood absence epilepsy. Zarontin is also effective in controlling absence seizures in many of these children, but other seizure medicines often are needed to control other types of seizures. Depakote or medicines related to it will control absence seizures, so it may be used instead of Zarontin. Some children do best with a combination of these two.

Zarontin can also be used in combination with other seizure medicines for patients who have other kinds of seizures in addition to absences. No single combination of antiepileptic medications is perfect for everyone. Sometimes, a series of combinations must be tried before finding what is best for the individual patient. Adding Zarontin usually does not affect the level of other seizure medicines in the body, but some adjustment of the Zarontin dosage may be needed if other medications are added.

In rare cases, Zarontin has been reported to worsen generalized tonic-clonic seizures.

Reviewed February 2004 by Barry Gidal, PharmD, epilepsy.com Editorial Board.