Lamotrigine

Lamotrigine is an anti-convulsant used in the treatment of a broad range of seizures and in conditions such as bipolar disorder. Lamotrigine is rapidly absorbed from the gastrointestinal tract and undergoes extensive metabolism. Steady state plasma concentrations are usually achieved at around five days however lamotrigine exhibits autoinduction within the first two weeks of commencing therapy which may prolong time to steady state. The metabolism of lamotrigine is affected by the use of concomitant enzyme inducers (e.g. carbamazepine, phenytoin) and inhibitors (e.g. sodium valproate) altering its half-life in adults from a mean of 24-35 hours to between a mean of approximately 14 and approximately 70 hours respectively. Plasma concentrations appear to overlap between responders and non-responders and between those patients experiencing or not experiencing side effects. Toxicity occurs more frequently where plasma concentrations exceed 15 mg/L.