Bimodal gastroretentive drug delivery systems of lamotrigine: formulation and evaluation

Gastroretentive bimodal drug delivery systems of lamotrigine were developed using immediate release and extended release segments incorporated in a hydroxypropyl methylcellulose capsule and in vitro and in vivo evaluations were conducted. In vivo radiographic studies were carried out for the optimized formulation in healthy human volunteers with replacement of drug polymer complex by barium sulphate and the floating time was noted. Here the immediate release segment worked as loading dose and extended release segment as maintenance dose. The results of release studies of formulations with hydrophillic matrix to formulations with dual matrix hydroxypropyl methylcellulose acetate succinate shown that as the percentage of polymer increased, the release decreased. Selected formulation F2 having F-Melt has successfully released the drug within one hour and hydrophillic matrix composing polyethylene oxide with 5% hydroxypropyl methylcellulose acetate succinate showed a lag time of one hour and then extended its release up to 12th hour with 99.59% drug release following zero order kinetics with R(2) value of 0.989. The Korsmeyer-Peppas equation showed the R(2) value to be 0.941 and n value was 1.606 following non-Fickian diffusion pattern with supercase II relaxation mechanism. Here from extended release tablet the drug released slowly from the matrix while floating.