BEAD COATING PROCESS VIA AN EXCESS OF CROSS-LINKING AGENT

Coated beads were prepared by soaking in sodium alginate solutions sph erical matrices (beads) of carboxymethylcellulose crosslinked with alu minum chloride (AlCl3) and loaded with ambroxol hydrochloride as a mod el drug. The residual amount of the crosslinker induced an interfacial crosslinking reaction of the sodium alginate. Therefore, an insoluble , smooth and uniform in thickness coat was formed around the beads. As the coating time increased, the coat thickness increased untill AlCl3 was present inside the beads. The rate of drug release from the coate d beads was slower than that from the uncoated beads and decreased wit h the increase in coating time. Moreover, a constant rate phase, subse quent a burst period for the samples obtained with the highest coating times, was achieved. The dynamic swelling analysis allowed to exclude the influence of the polymer relaxation on the release process which appeared to be controlled by the alginate coat.