Lamotrigine clearance increases by 5 weeks gestational age: Relationship to estradiol concentrations and gestational age.

Gestational week was a better predictor of changes in LTG-CL/F than estradiol concentration and may reflect additional factors, although neither was robust enough to use clinically due to substantial interpatient variability. Changes in LTG-CL/F begin as early as the 5th gestational week, often before women know they are pregnant, emphasizing the importance of planning and early detection of pregnancy and consideration of early implementation of therapeutic drug monitoring. Ann Neurol 2018;84:556-563.