Vigabatrin is a second generation anticonvulsant drug available in France since 1995. It is an amino acid analogue of the GABA, marketed under the racemic form [R(-)/S(+)50/50], but only the S(+)-enantiomer is active. Neither the mechanism of action of vigabatrin, an irreversible enzymatic inhibition, nor its pharmacokinetic characteristics (no binding to plasma proteins, low metabolism, no interaction with CYP), are in favour of TDM. There is no validated therapeutic range, but to the recommended dosage of 1 to 3 g a day correspond plasma concentrations ranging from 0,8 to 36 mg/L (6 - 279 micromol/L). For this molecule, the level of proof of the interest of the TDM was estimated in: to be useless.