The influence of plasticizers on the release of theophylline from microporous-controlled tablets

The aim of present work was to investigate the influence of plasticizer on the release of theophylline from microporous-controlled tablets. Three plasticizers, acetyltributyl citrate (ATBC), castor oil, and triacetin, were included in this study. These plasticizers reduced the crystallinity of poly(epsilon-caprolactone) (PCL)/poly(ethylene glycol) (PEG)-blended films, and the most prominent change of enthalpy of fusion was the film plasticized by triacetin. This might be due to triacetin penetrating into both PCL and PEG domains. However, the lipophilic property of castor oil only allowed it to alter the crystallization of hydrophobic PCL domain. The Young's modulus and the tensile strength of films showed a decreased tendency while increasing the amount of plasticizer. The change of elongation of plasticized blended films was irregular and was dependent of the type of plasticizer. The size of micropores formed in the presence of plasticizer was larger than those micropores formed in its absence. The fatty plasticizer, castor oil, altered the thermal and mechanical performance and pore size of films via soluble in PCL domain, which resulted in the release of theophylline from castor oil plasticized-coated tablets, which in turn enhanced and closed to a constant release pattern. (C) 2004 Elsevier B.V. All rights reserved.