In a trial to delay the release rate of diclofenac sodium from alginate coated
microcapsules, the use of a copolymer was suggested. Mixtures of polymers can have a
significant properties than that of individual polymer to achieve sustained release
microcapsules. On considering the negative charge of alginate and its ability to form polyionic
complexes with a lowered tendency of erosion at higher pH value, a cationic polymer was
seeked. Chitosan (CS) was the one of choice due to the similarity of the saccharide structures of
chitosan and alginate that offers greater interaction between the two polymers and stronger
inter-chains reactions relative to that between alginate and branched polymers such as
polylysine. The microcapsules prepared using 0.1 and 0.25% (CS) were spherical in shape
while 0.4% (CS) formed microcapsules having rounded heads and tapered tails. The change in
chitosan concentration had a non-significant effect on the particle size, the yield and the drug
loading efficiency. The releaser ate of diclofenac sodium from microspheres showed a pHdependent
profile and was affected by chitosan coating. The release rate of diclofenac sodium
from chitosan coated alginate microcapsules at pH 7.4 was found to be faster than its release at
pH 1.2. These results suggest this coating method to protect diclofenac sodium under acidic
conditions and to permit a complete but controlled release of diclofenac sodium.