What is the lowest possible dose of lamictal which would be considered therapeutic for seizures? My brother age 60, has an old head injury,since 1975. He has had only 3 seizures since then. His current dose is 100 mg at night, 50 mg in am. We continue to see speech problems and some coordination issues,which we associate with too much lamictal. Would like to lessen dose,but retain therapeutic dose.