Open study evaluating lamotrigine efficacy and safety in add-on treatment and consecutive monotherapy in patients with carbamazepine- or valproate-resistant epilepsy

Lamotrigine is a broad-spectrum antiepileptic drug that blocks sodium channels, thereby inhibiting the pre-synaptic release of excitatory neurotransmitters. The primary aim of the study was to evaluate lamotrigine add-on therapy and consecutive monotherapy in patients with epilepsy whose seizures were not controlled by carbamazepine or valproate. One hundred and twenty six epilepsy patients at 18 centres in Poland were recruited into a lamotrigine substitution study. In all patients, existing seizures were poorly controlled with valproate (n= 63) or carbamazepine (n= 63) monotherapy. The study consisted of four phases: (1) a 4-week lamotrigine dose-escalation phase, (2) an 8-week lamotrigine add-on phase, (3) an 8-week carbamazepine/valproate withdrawal phase, and (4) an 8-week lamotrigine monotherapy phase. Of 126 patients recruited into the study, 107 (85%) completed dose-escalation and add-on therapy with lamotrigine and 85 (68%) completed lamotrigine monotherapy. Fifty percent of patients during add-on therapy and 53% during lamotrigine monotherapy experienced at least 50% reduction in total seizures (responders) compared to the pre-study period. Approximately 20% of patients during add-on therapy and 27% during lamotrigine monotherapy were seizure free. Total well-being was assessed using a Visual Analogue Scale with 62% of patients during add-on therapy and 60% in lamotrigine monotherapy reporting improvement in scores. Lamotrigine was generally well tolerated. Treatment was discontinued in 7% because of adverse events. In conclusion, lamotrigine is an effective AED in add-on therapy and monotherapy, it is safe and well tolerated, and successful conversion from add-on to monotherapy can be achieved in many cases. An additive effect between lamotrigine and valproate was observed.