Randomized, controlled studies add-on studies of Lamictal in patients with refractory partial seizures found that Lamictal reduces seizure frequency by at least half in 16% to 20% more patients than add-on placebo (Messenheimer et al. 1994). Side effects were more troublesome than with the placebo, but they were generally minor and often went away without stopping the medication.

Lamictal is also used to treat absence, myoclonic, and tonic-clonic seizures. It is effective against some seizure types in patients with Lennox-Gastaut syndrome and other forms of symptomatic generalized epilepsy. In one study using Lamictal as add-on therapy for patients with Lennox-Gastaut syndrome, 23% more patients who took Lamictal (compared to a placebo) had the number of their tonic-clonic seizures cut at least in half (Motte et al. 1997). Nearly half of the patients who took the Lamictal had less than a 25% decrease in these seizures, however.

Studies have also looked at the effectiveness of Lamictal used alone. In one study (Brodie et al. 1995), patients with newly diagnosed epilepsy were treated with either Lamictal or carbamazepine (Tegretol, Carbatrol). A similar study (Steiner et al. 1999) compared Lamictal to phenytoin (Dilantin, Phenytek). The patients in these studies had partial seizures with or without secondary generalization, or they had primary generalized tonic-clonic seizures. In each study, the effect on the frequency of each seizure type was almost the same for both medications, but the patients taking Lamictal had fewer problems with side effects.