Comparative studies on polyelectrolyte complexes and mixtures of chitosan-alginate and chitosan-carrageenan as prolonged diltiazem clorhydrate release systems.

The aim of this work was to evaluate the possibility of using mixtures and/or polyelectrolyte complexes from both chitosan-alginate and chitosan-carrageenan as prolonged drug release systems. Different dissolution profiles were obtained by changing the polymer matrix system (chitosan-alginate or chitosan-carrageenan) and the method used to include these polymers into the formulation (physical mixture or polyelectrolyte complex). Drug dissolution profiles from the matrices have been discussed by considering the swelling behavior of the polymers used. The swelling behavior of the chitosan-carrageenan and chitosan-alginate systems was analyzed by using the Hopfenberg model which permits to separate the diffusional contribution, kf, from the relaxational contribution, kr, involved in solvent penetration/sorption in glassy polymers. The chitosan-alginate system is better than the chitosan-carrageenan system as prolonged drug release matrix because the drug release is controlled at low percentage of the polymers in the formulation, the mean dissolution time is high, and different dissolution profiles could be obtained by changing the mode of inclusion of the polymers. Good agreement between td and kf/kr values for the system chitosan-alginate was found, which means that the swelling behavior of the polymers controlled the drug release from the matrix. In the case of the system chitosan-carrageenan, the high capacity of carrageenan promotes the entry of water into the tablet and therefore the main mechanism of drug release would be the disintegration instead of the swelling of the matrix.