Tiagabine, a second-generation anticonvulsant drug, is marketed in France since 1997. It is also prescribed outside marketing authorization in the treatment of anxiety. They are few studies allowing arguing a relation exposure efficiency or toxicity, but intra and inter individual important variations in serum concentrations are described. Hepatic insufficiency requires a dose adaptation. In patients treated with therapeutic dose, serum levels are between 20 and 100 microg/L (50-250 nmol/L). For this molecule, the level of proof of the interest of TDM was estimated in: remaining to estimate.