In vivo biopharmaceutical characterisation of a new formulation containing the antiepileptic drug lamotrigine in comparison to plain and dispersible/chewable lamotrigine tablets

Aim: Two studies in healthy male volunteers were carried out to evaluate the pharmacokinetic profile of a new divisible formulation of lamotrigine (CAS 84057-84-1, Plexxo®, Lamotrigin Desitin®) in plasma in comparison to plain or dispersible lamotrigine tablets. Methods: The plasma pharmacokinetics of lamotrigine were analysed after administration of single doses of 100 mg lamotrigine given as one tablet of the new formulation and either the plain or the dispersible reference formulation in two separate studies. In each study the data of 24 subjects were analysed according to the study protocol. Venous blood samples were taken at appropriate intervals up to 120 h after dosing. Concentrations of lamotrigine were determined in plasma by a validated HPLC method using UV detection. Results and conclusion: In both studies, mean plasma concentration-time profiles of the new lamotrigine formulation and both reference formulations ran nearly In parallel. The pharmacokinetic mean data calculated from different subject groups of the two studies were very similar. The mean ratios of the main pharmacokinetic parameters and the corresponding 90% confidence intervals of AUC_0-t, AUC_0-inf and C _max were 103 % (99.7-105.7), 103% (99.6-107.3) and 101% (95.2-106.6) for the comparison with the plain lamotrigine tablet and 100% (98.0-102.8), 100% (96.5-102.8) and 102% (99.1-105.3) for the comparison with the dispersible/chewable tablet, respectively. The most frequently reported adverse events possibly related to the administration of lamotrigine were headache and dizziness in both studies. It is concluded that the new divisible lamotrigine formulation is bioequivalent with regard to rate and extent of absorption to both the plain reference lamotrigine product and to the dispersible/chewable reference product.