Effect on drug release of mixed matrixing polymers (sodium alginate and HPMC K15M with chitosan).
Various ratios of sodium alginate and chitosan (2:1, 1:1, and 2:3) were taken and the dissolution profiles were obtained.
Care was taken to prevent loss of integrity of the tablets. The increase in the drug profiles of all the three batches shows
the significance of the incorporation of chitosan. This increase was directly proportional to the drug release from the hydrophilic
matrices. Although the initial burst effect for batches SC1, SC2, and SC3 were 19.98%, 20.61%, and 22.58%, respectively (which
were close to the required theoretical value), the in vitro drug release was slowed down by the end of 8 h, that is, 78.91%, 87.88% and 89.82%. The similarity factor f
for batch SC3 was the only one above 50 (i.e., 51.17).
Figure 2: Effect of drug release of mixed matrixing polymers (sodium alginate and HPMC K15M with chitosan).
Other ratios of HPMC K15M and chitosan (4:1, 8:3, 2:1) were tried. The ratios were selected to reduce the possibility of a
loss of tablet integrity. The release profile was proportional to the content of the mixed polymers in the matrix. The initial
burst effect for batches HC1, HC2, and HC3 was 21.65, 22.02, and 24.59%. respectively (see Figure 2). After 8 h, these values
were 89.84, 91.58, and 94.55%, respectively. Results obtained showed all similarity factors above 50 (i.e. 55.25, 60.42, and
76.50 for batches HC1, HC2, and HC3, respectively).
Based on the release profiles, results of tablets containing HPMC K15M and chitosan were better than those of tablets made
with sodium alginate and chitosan. One could conclude that the formation of a rubbery type matrix by the sodium alginate in
the acidic medium was the hindrance in complete or sufficient drug release by 8 h.
Effect of low-density copolymer PSDVB on the release profile of floating matrix tablets containing HPMC K5M and chitosan.
To study the effect of drug release and buoyancy of a low-density copolymer (PSDVB) on the in vitro buoyancy and drug dissolution profile of various matrix-forming agents, formulation batches HC3–HC6 containing 40 mg each
of HPMC K15 M, and 15 mg of chitosan as matrixing agent with 0, 20, 30, and 40 mg of PSDVB copolymer (i.e., 0 8.2, 11.6, and
15.21%) were prepared. Results obtained from the in vitro dissolution study of floating matrix formulations of mixed polymers with PSDVB copolymer revealed that there was not a major
difference observed in drug dissolution profile with the variation in the percentage (see Figure 3). The drastic change in
the floating lag times occurred with the inclusion of varyious percentages of PSDVB low-density copolymer.
Figure 3: Effect of poly(styrene divinyl benzene) polymer on drug release from HPMC K15M and chitosan mixed matrix tablets.
Drug release in the first hour for HC3, HC4, HC5, and HC6 was between 21 and 25%. Drug release after 8 h was > 90%. The similarity
for batches HC3–HC6 was 76.50, 56.52, 81.66, and 56.46, respectively. During the in vitro buoyancy test, a significant change was observed in the floating lag time of the formulation with an increased amount of
PSDVB. Desired floating of the tablets was not achieved in lower concentrations of PSDVB copolymer (i.e., up to 8%). The floating
lag time for batch HC5, which contained approximately15% concentration of the low density copolymer, was 0 s.