The effect and safety of loreclezole were evaluated during a long-term follow-up trial targeting higher plasma concentrations than those of the preceding controlled trial. The result is better than in the double-blind trial, in which loreclezole doses were administered to reach plasma concentrations of 1-2 mg/l and 6/32 patients (19%) of the verum group experienced a seizure reduction of 50% or more. None of the 30 placebo-treated patients experienced a similar decrease. At the end of the double-blind trial, 56 patients (29 from the original loreclezole and 27 from the original placebo group) elected to participate in the open follow-up trial. After 12 months' add-on treatment with loreclezole, mean plasma concentrations of 5.53 and 5.97 mg/l for the original placebo and loreclezole group were measured and the median decreases in seizure frequency were -44% and -40. At these concentrations, 22/56 patients (39%) showed a seizure reduction of at least 50%.