PREPARATION AND EVALUATION OF TIMOLOL MALEATE MATRIX TABLET USING HYDROGEL FORMING POLYSACCHARIDES

Matrix tablets of timolol maleate were prepared using hydrogel forming natural polysaccharides like sodium alginate, xanthan gum and guar gum alone and with hydrophobic polymers like ethyl cellulose and hydroxyethyl cellulose by direct compression method. The Fourier-transform infrared spectroscopy of drug-polymer and polymer-polymer was studied and revealed the compatibility of drug and polymer. All the precompression parameters like angle of repose, bulk density, tapped density, Carr’s index and Hausner’s ratio for drug polymer mixture were found within limits of pharmacopeial specification. The tablets were studied for post compression parameters like hardness, thickness, weight variation and drug content were in acceptable range of pharmacopeial specification. The tablets were studied for invitro swelling index, invitro drug release study. The effect of hydrophobic polymers like ethyl cellulose and hydroxy ethyl cellulose were also studied on invitro swelling and drug release. The scanning electron micrography was done for selected swellable matrix tablets revealed that the tablets containing guar gum and hydroxy ethyl cellulose (F9) showed compact structure with fewer cracks. All the matrix tablet showed good swelling up to 12 h maintaining integrity of formulation in rank order of xanthan gum> guar gum> sodium alginate. The invitro release of timolol maleate from matrix tablet was 80-90% and extended up to 10 to 12 h for xanthan gum, guar gum, sodium alginate alone and in combination with ethyl cellulose and hydroxy ethyl cellulose. The addition of hydrophobic polymer hydroxy ethyl cellulose showed good swelling with prolonged release as compare to ethyl cellulose. The results of invitro swelling correlated with invitro release. The invitro release followed the rank order of xanthan gum> guar gum> sodium alginate. The invitro release obeyed first order kinetic with mechanism of release was diffusion control. The similarity factor calculated for selected formulations F9, F8 and F7 containing guar gum, xanthan gum and sodium alginate along with hydroxy ethyl cellulose showed good similarity with theoretical extended release profile.  Hence these combinations could be used to prepare extended release timolol maleate matrix tablets having prolonged therapeutic effect.