Development of extended release divalproex sodium tablets containing hypdrophobic and hydrophilic matrix

Bilayered tablets of Divalproex sodium for once-a-day administration were prepared using a hydrophilic and hydrophobic polymer as release retarding agents. This technology was found to be more effective than a simple matrix tablet with a mixture of the above polymers in order to retard the drug release for a period of 24 h. The drug release profile was strongly dependent on the presence of wicking agent, pathlength of hydrophobic layer, and hardness of tablet. f(1) value of 6.92 and f(2) value of 76.72 indicated similarity between the release profiles of batch BT3 and reference tablet (Depakote((R)) ER) with the target release of over 55% within 12 h and over 85% within 18 h. Mathematical modeling using Korsmeyer-Peppas equation indicated that the release followed a combination of diffusion and erosion mechanism.