Calcium Caseinate: A New Matrix for Sustained Delivery of Oral Drugs

Abstract

Calcium caseinate beads containing the drug theophylline were prepared by dropping a 20% aqueous alkaline solution of casein containing the drug through a 22 G hypodermic needle into calcium chloride solutions of different concentrations. The in-vitro release of the drug into gastric and intestinal fluids in the absence of enzymes was examined at 37°C using a paddle-type dissolution assembly. The release into gastric fluid was found to be a function of the concentration of calcium chloride employed for cross-linking the matrix and the extent of drug loading. Surprisingly, neither cross-linking density nor extent of loading had any effect on drug release into intestinal fluid and almost 100% was released in about 3 h. Drug release into gastric fluid could be limited to less than 10% in 24 h by varying the cross-linking density and loading. Data obtained suggest that calcium caseinate would be suitable as a matrix to deliver drugs that are well-absorbed only within the confines of the small intestine and to protect drugs that are unstable in the pH range of gastric juice.