Fabrication of chitosan--polyacrylic acid complexes as polymeric osmogents for swellable micro/nanoporous osmotic pumps.

AIM: The aims of this study were to prepare and evaluate chitosan-polyacrylic acid complex (CS-PAA) as polymeric osmogents for swellable micro/nanoporous osmotic pump propranolol tablets. METHODS: The complexes were characterized and evaluated for their swelling characteristics. The selected complexes were incorporated into the core propranolol tablets as polymeric osmogents. The core tablets were formulated, compressed as monolithic and two-layered tablets, and finally coated with cellulose acetate containing PEG 400 and PVP K30 as plasticizers and pore formers, respectively. As a final point, the drug release was determined. RESULTS: A direct correlation was found between the CS content in the complex and the maximum swelling force and swelling ratio of the complex mixture. In vitro drug release revealed that the percent drug release increased with the amount of osmogent in the two-layered tablets. Drug release could be prolonged up to 12h and conformed to the USP 31 criteria. In contrast, percent release decreased with the increasing amount of complexes in monolithic tablets. It was postulated that two opposing mechanisms were involved. Following water uptake, the complexes of polymers swelled and pushed the drug out of the tablets, and the drug bound to the polymer network and remained in the tablets. CONCLUSIONS: The results indicated that the complex of CS-PAA at optimal proportion and amount was a promising polymeric osmogent for a zero-order controlled release from two-layered swellable micro/nanoporous osmotic pump tablets.

Development and optimization of micro/nanoporous osmotic pump tablets.

Micro/nanoporous osmotic pump tablets coated with cellulose acetate containing polyvinylpyrolidone (PVP) as pore formers were fabricated. Propranolol hydrochloride was used as a model drug in this study. Formulation optimization based on USP 31 requirements was conducted following a central composite design using a two-level factorial plan involving two membrane variables (pore former and coating levels). Effect of molecular weight of pore former (PVP K30 and PVP K90) was also evaluated. Responses of drug release to the variables were analyzed using statistical software (MINITAB 14). Scanning electron microscopy and atomic force microscopy showed that the pores formed by PVP. The drug release was dependent on the molecular weight and concentration of PVP and the level of coating. The results showed that acceptable 12-h profile could be achieved with only specific range of PVP K30-containing membrane at the defined membrane thickness. However, satisfactory 24-h profile could be accomplished by both PVP K30 and PVP K90-containing membrane at the range and membrane thickness tested. Preparation and testing of the optimized formulation showed a good correlation between predicted and observed values.