Enhanced solubility and dissolution rate of lamotrigine by inclusion complexation and solid dispersion technique

The solid-state properties and dissolution behaviour of lamotrigine in its inclusion complex with beta-cyclodextrin (beta CD) and solid dispersions with polyvinylpyrrolidone K30 (PVP K30) and polyethyleneglycol 6000 were investigated. The phase solubility profile of lamotrigine with beta CD was classified as A(L)-type, indicating formation of a 1:1 stoichiometry inclusion complex, with a stability constant of 369.96 +/- 2.26 M-1. Solvent evaporation and kneading methods were used to prepare solid dispersions and inclusion complexes, respectively. The interaction of lamotrigine with these hydrophilic carriers was evaluated by powder X-ray diffractometry, Fourier transform infrared spectroscopy and differential scanning calorimetry. These studies revealed that the drug was no longer present in crystalline state but was converted to an amorphous form. Among the binary systems tested, PVP K30 (1:5) showed greatest enhancement of the solubility and dissolution of lamotrigine.