Evaluation of ethylcellulose as matrices for controlled release drug delivery

As the efficiency of a matrix forming polymer in sustaining drug release is a multiple function of physico-chemical nature of the active ingredient and pH of the surrounding environment, the study was undertaken to evaluate the effect of pH of dissolution media on the release profile of three drug molecules with diversified physico-chemical properties. Matrix tablets of diclofenac sodium, theophylline and diltiazem HCl were prepared using ethylcellulose as the matrix forming agent. The drug dissolution behavior of the matrix tablets were studied over 10 hours in buffer media of pH 1.2, 4.5 and 6.8. Elevation of pH of the dissolution medium increased the rate and extent of diclofenac release. However, for diltiazem HCl, increasing the pH showed the reverse pattern. Theophylline release, on the other hand, seemed to be unaffected by the pH of the dissolution media. This can be correlated with the physico-chemical characteristics of the drugs. Effect of compression force on drug release and tablet hardness was also studied. Increasing the compression force reduced drug release irrespective of the chemical nature of the drug molecule which can be attributed to the reduction of porosity and formation of continuous polymeric network within the matrix. Again, no significant change in tablet hardness was found with the increment of compression force. A near zero-order release kinetics were observed in all formulations investigated.