Controlled release of chitosan film coated tablets by osmotic and diffusion machanisms

Abstract

The purpose of this present study was to apply chitosan as a main component of film formation in propranolol hydrochloride osmotic pump device. The coated film consisted of chitosan acetate, magnesium stearate, castor oil and brilliant blue. Molecular weight of chitosan had an influence on drug release. The coated tablets with lower molecular weight of chitosan exhibited slower drug release than those with higher molecular weight. Thus, the lower molecular weight was chosen to apply as coating material for coated tablets. Moist heat treatment at 60 ℃ 75%RH to the coated tablets was effective to prolong drug release, due to the thermally-induced conversion of a water-soluble chitosan acetate film into a water-insoluble chitin film. Therefore, prolongation of drug release and lag time depended on the interval of moist heat treatment. Having passageway was a method to decrease lag time and increase drug release. After long moist heat treatment, the coated film was integrity, durable but lower water permeability. Influence of passageway on drug release was also obtained, whereas the effect of the size of passageway on drug release was minute. Increasing the osmolality of dissolution medium led to a decrease in dissolution profile of treated tablets, indicating that osmotic pressure had an effect in the control of the release of propranolol hydrochloride. Incorporation of sodium chloride into core tablets further prolonged the drug release. The drug release characteristics could be explained in terms of the diffusion controlled and osmotically driven force.