Comparison of the characteristics of several polymer materials used in hydrophilic matrix tablets

Pure and drug hydrophilic matrix tablets were prepared by direct compression method with theophylline as a model drug.  The characteristics of four hydrophilic matrix polymers, hydroxypropylmethylcellulose (HPMC), polyethylene oxide (PEO), sodium alginate (NaAlg) and xanthan gum (XG), were compared by investigating the water absorption, swelling, erosion and gel layer strength.  The sequence of water absorption rate was XG >> NaAlg (H) > PEO > NaAlg (L) >> HPMC; The sequence of swelling index was XG >> PEO >> HPMC >> NaAlg; The sequence of erosion rate was NaAlg (L) > NaAlg (H) >> PEO80 > PEO200 > PEO300 > XG ≈ PEO400 ≈ K4M > K15M > PEO600 ≈ K100M; The sequence of the gel layer strength was PEO > HPMC > XG >> NaAlg.  For the PEO and HPMC matrix tablets, with the polymer molecular weight increased, the drug release mechanism was gradually transferred from mainly depending on the erosion to the diffusion; for SAL matrix tablets, the drug release mainly depends on erosion mechanism; and for XG matrix tablets, the drug release mainly depends on non-Fick diffusion mechanism.  Comparison of the performance difference between the polymer materials will contribute to rational design and prediction of drug release behaviors from matrix tables and ultimately to achieve clinical needs.