Lamictal (lamotrigine) is approved by government agencies in most countries to be used as an add-on medicine for adults whose partial seizures are not well controlled by another seizure medicine. Doctors have studied groups of people who have used Lamictal in this way, comparing them with other patients who were given pills with no medicine in them (called a placebo). The doctors counted how many people had their seizures reduced by at least half. They found that 16% to 20% more people who took Lamictal met that standard than ones who took the placebo. The people who took Lamictal had more trouble with side effects, but the side effects were generally minor and often went away without stopping the medicine.

Lamictal is used to treat several different types of seizures. In one study, Lamictal was given as an add-on medicine for patients with the pattern of seizures called Lennox-Gastaut syndrome. Compared to patients who were given a placebo, 23% more patients who took Lamictal had the number of their tonic-clonic seizures cut at least in half. Many of the other patients who took the Lamictal had little improvement, however.

No single combination of seizure medicines is perfect for everyone. Sometimes a series of combinations must be tried before finding what is best for the individual. Many other seizure medicines affect the way the body uses Lamictal, so the amount of each medicine that the person takes may need to be adjusted.

Some other studies have compared Lamictal with other seizure medicines when they are used alone, to see which medicine is best for people who have just begun treatment for epilepsy. On average, the results were about the same for Lamictal as for some other seizure medicines that are often used, but the patients in these studies who took Lamictal had fewer problems with side effects.