Purpose: Intravenous (IV) formulations are useful when treating patients where oral administration is not possible and to study certain pharmacokinetic parameters such as bioavailability. We developed a stable-labeled IV formulation of lamotrigine (LTG) for studying pharmacokinetics in epilepsy patients.Methods: Stable-labeled IV LTG was given to 20 persons with epilepsy (6 men; 14 women) with a mean age of 34.8 years (SD 11.7). A 50mg dose of LTG (stable labeled) was given intravenously and replaced 50mg of the regular morning oral dose of LTG (unlabeled, commercially available formulation).Results: No significant changes in blood pressure, heart rate, or adverse events including rash were attributed to administration of a 50-mg dose of the intravenous LTG formulation.Conclusion: Our results show that LTG base that is complexed with 2-hydroxypropyl-β-cyclodextrin and stable-labeled can be given safely as a tracer replacement dose.