Lamotrigine is a second generation anticonvulsant drug available in France since 1996. As other anticonvulsant drugs, lamotrigine is also used in type I bipolar disorders and except legal notices, in the treatment of neuropathic pains. It is mainly metabolized by the UDP-glucuronyltransferase in inactive metabolites. Its average half-life of elimination is of the order of 22 h, but it is reduced approximately at 14 h if it is associated with enzymatic inductors and increased at 70 h if lamotrigine is administered with sodium valproate. The pharmacokinetic parameters are modified at the young child's, but not in the old population. During the pregnancy, the plasmatic concentrations are lowered and re-increase strongly after the delivery, if dosages were adapted. The renal insufficiency does not require adaptation of dosage, on the other hand in case of severe hepatic insufficiency a decrease of the dose is to be considered. The correlation concentration-efficiency does not seem demonstrated, but there are not enough published studies and they included few patients. Furthermore, they were led with a methodology more pragmatic than rigorous. The correlation concentration-toxicity is better argued. The recommended therapeutic range is from 2.5 to 15 mg/L. For this molecule, the level of proof of the interest of the TDM was estimated in: possibly useful.