Evaluation and Optimization of Preparative Variables for Controlled-Release Floatable Microspheres Prepared by Poor Solvent Addition Method

Abstract

The aim of this study was to evaluate and optimize preparative parameters for floatable theophylline microspheres prepared by the emulsion–solvent evaporation method. A three-factor three-level Box–Behnken design was employed using amount of poor solvent, temperature-increase rate and drug loading as independent factors, and percentage floating at 3 h and time required for 50% drug release as dependent variables. Simultaneous optimization of the parameters for maximum buoyancy and desirable drug release was conducted using a partitioned artificial neural network. A microsphere using 27.6% of drug loading, 0.29°C/min of temperature-increase rate, and 1.7 mL of poor solvent was identified for maximizing buoyancy and sustaining drug release.

Keyworkds:

• floatable microsphere
• sustained release
• solvent evaporation
• poor solvent addition
• optimization
• theophylline

ACKNOWLEDGMENTS

The authors are grateful to Meito Sangyo Co., Ltd. (Nagoya, Japan) for supplying PDME. The authors are also grateful to Mr. Y. Seki for kind assistance in the experimental work.