Lamotrigine by immunoassay
Lamotrigine (Lamictal) was first licensed for use as an anti-convulsant in 1994 for the treatment of partial seizures. It has now been licensed for use in monotherapy in adults and children, for both partial and primary and secondary tonic-clonic seizures. Lamotrigine is also widely used as a mood stabiliser in bipolar disorders. The measurement of lamotrigine levels is useful for tailoring treatment for an individual, particularly if poor compliance or toxicity are suspected. The half life of lamotrigine is around 25 hours, but this is significantly affected by many other drugs, especially other anti-convulsants such as carbamazepine, valproate and phenytoin. Large inter-individual variations in the dose/concentration exist and there is a therapeutic range in which lamotrigine is effective and unlikely to lead to severe side effects. Lamotrigine toxicity presents in a similar way to carbamazepine, and therapeutic drug monitoring can help in this diagnosis.