Doctors have studied large numbers of patients with partial seizures to find out how well Trileptal works. In studies where patients took either Trileptal by itself, or phenytoin (Dilantin, Phenytek), valproate (Depakote), or carbamazepine (Tegretol, Carbatrol) alone, Trileptal controlled seizures as well as the other medications.

Other studies have shown that Trileptal works well when added to other seizure medications. Trileptal is not a perfect add-on seizure medicine for everyone, however. Sometimes people must try a series of combinations before finding what is best for them. But because Trileptal doesn't interact much with other medicines, it can be used as an add-on without the need for complicated changes in dosage. The one exception is that adding Trileptal to phenytoin (Dilantin, Phenytek) can cause the amount of phenytoin in the blood to rise.