Potential and mechanism of A-Tab as a controlled release agent

This study investigated the mechanism by which anhydrous calcium phosphate [A-TAB] exhibits its sustained release matrix, via premixing of A-TAB [diluent] powder with different excipients, e.g. Avicel, sodium alginate and polyvinyl alcohol [PVA], to block entrapment sites if any, on the dissolution of theophylline from A-TAB tablets. Furthermore, the inclusion of other excipient [palmetic acid] to impart a more acid resistant character on the diluent/drug blend and thus assist in maintaining the matrix structure of A-TAB were also investigated. The rate and extent of drug dissolution were dependent on the order of mixing of A-TAB with the drug and excipient as well as the pH of the dissolution medium