[The use of bead cellulose for controlled drug liberation. 5. Binding of benzocaine as a model drug to dialdehyde-bead cellulose and its in vitro liberation].

In the case of ionic binding of drugs to bead cellulose and its derivatives there was no pronounced retardation obvious. Because of this lack benzocaine as a model drug was covalent bound to dialdehyde bead cellulose by an azomethine bond in analogy with enzyme immobilisation methods. The rate of liberation in phosphate buffer was low and incomplete compared with the dissolution rate of pure benzocaine under the same conditions. A further decrease of liberation rate was obtained by reduction of the azomethine to the amine bond. Retardation of drug liberation strictly speaking was not achieved. The main amount of liberated drug was liberated during the first 20 min, but after 6 h the rate was still under 50% of the drug available. The physical properties of the beads like spherical shape and porosity are not significantly influenced by oxidation of cellulose and by loading with drug.