Porous cellulose matrices containing lipophilic release modifiers--a potential oral extended-release system

A multiple-unit extended-release matrix preparation was prepared by the incorporation of a hydrophilic drug (paracetamol) and lipophilic release modifiers (cetyl alcohol and paraffin) into porous cellulose matrices. The incorporation was performed using a one-step melt method. The in vitro drug release could be extended up to at least 16 h. The release rate could be controlled by varying the ratio of cetyl alcohol to paraffin. The porosity of the matrix during release increased to a larger extent than explainable by dissolution of the drug substance. This increase in porosity appears to be caused by swelling of the cellulose in combination with some erosion of the matrix material.