Oxcarbazepine long-term treatment retention in patients switched over from carbamazepine

We evaluated the long-term outcome of oxcarbazepine (OXC) monotherapy in a population of patients switched over from carbamazepine (CBZ) monotherapy. Subjects of the study were recruited among patients who had successfully completed the PRIMO study, a recent multicentre Italian study that assessed the therapeutic equivalence of immediate (overnight) and more progressive switching from CBZ to OXC monotherapy in patients with partial seizures unsatisfactorily maintained on CBZ monotherapy due to poor tolerability or scant clinical efficacy. Treatment retention rate was chosen as a composite parameter for both efficacy and tolerance of OXC. Twelve months after having completed the PRIMO study, 91 of 105 patients (87%) were still taking OXC, 80 of them (76%) as monotherapy. Mean OXC dose was 1250+/-459 mg/day. Eighty-four out of 105 patients (80%) rated OXC tolerability as "good" or "very good". The mean ratio of the last dose of OXC to the last dose of CBZ increased from 1.54 (end of PRIMO study) to 1.69 (end of follow-up). The large majority of a population of patients who were successfully switched from CBZ monotherapy to OXC monotherapy maintained OXC treatment for at least a further 12 months. The 1.5 OXC/CBZ ratio appears to be close to the optimal for the switch from CBZ to OXC, at least in patients treated with CBZ monotherapy.