Doctors have studied large numbers of people to find out how well valproic acid and the other valproate medicines control seizures. (There is hardly any difference in the way the different valproate medicines work.) They have reported that these medicines are very good at completely controlling absence seizures in many people who take them. In another group, over 80% of people with new tonic-clonic seizures and related types didn't have any seizures during the period when they were given a medicine like valproic acid.

These promising results are not always matched in everyday life. Sometimes people don't take all their medicine on time. Not everyone's seizures can be controlled at a dose that can be taken without side effects. Because of individual differences, there is no "best" amount for everyone. Adjustments are often needed to reduce seizures or side effects.

In studies of seizure medicines, some people do better with valproic acid and others do better with something else. It's difficult to forecast the results for any given person. Differences in side effects may be important in deciding which medicine is best for each person.

If seizures continue, the doctor probably will change the amount of valproic acid prescribed. If that doesn't work, the next step may be either to prescribe a different seizure medicine by itself or to prescribe a combination of valproic acid and another seizure medicine. Many are available. No single combination is best for everyone. Valproic acid is often used as an "add-on" medicine for people who continue to have certain kinds of seizures while taking other seizure medicines.