Many people who take Zarontin don't have any trouble with side effects. The most common complaints (usually not too severe) are problems like upset stomach, loss of appetite, or diarrhea. These problems are usually mild and often they go away by themselves. If they are really bothersome, call the doctor. Usually reducing the amount of Zarontin or taking it with meals will help, but don't stop taking Zarontin or change the way it's taken unless the doctor says it's OK to do that.

A few people become sleepy or dizzy when they take Zarontin, so those who have just started taking it should be careful during activities that might be dangerous, until they know how it affects them.

Allergic reactions
Some people who take Zarontin have a red rash within the first few weeks of taking it. If this happens, tell the doctor or nurse right away, to be sure that it's not the beginning of a serious problem. It's rare for the rash to be serious, but don't ignore it. It's often necessary to switch to a different seizure medicine.