ABSTRACT
<p><b>OBJECTIVE</b>To investigate the feasibility of swelling hydrogel instead of polyethylene oxide as swelling polymer in push-layer of push-pull osmotically controlled-release tablets.</p><p><b>METHOD</b>The swelling patterns of tablets made of pure polymers were studied by immerging the tablets into purified water and testing their size at different time points. The push-pull osmotic-pump tablets were prepared and their release patterns in vitro were studied and compared by their similar factor (f2).</p><p><b>RESULT</b>Tablets with different swelling materials all showed satisfying release pattern in vitro and their release ratio at 12 h were all above 80%.</p><p><b>CONCLUSION</b>With its release rate and cumulative release percentage at 12 h, the mixture of HPMC K15M and CMCNa in ratio of 1:1 is the best choice instead of polyethylene oxide as swelling polymer in push-layer.</p>