FORMULATION AND EVALUATION OF DICLOFENAC CR TABLETS EMPLOYING CROSS LINKED STARCH UREA- A NEW MODIFIED STARCH

Controlled release drug delivery systems are aimed at controlling the rate of drug delivery, sustaining the duration of therapeutic activity and / or targeting the delivery of the drug to a tissue. Drug release from these systems should be at a desired rate, predictable and reproducible. Polymers which are used as release-retarding materials in the design of controlled release drug delivery systems play a vital role in controlling the delivery of drug from the systems. Though a wide range of polymers and other release retarding polymers are available, there is a continued need to develop new and more efficient release retarding polymers for controlled release.The objective of the present study is to develop a new release – retarding and rate controlling polymer for controlled release. Starch-urea cross-linked with calcium, a new modified starch was synthesized and evaluated for its application in the formulation of controlled release tablets of diclofenac. Controlled release formulation is needed for diclofenac because of its short biological half life of 2.0 h, and also to minimize GI disturbances such as peptic ulceration with bleeding. Diclofenac (100 mg) matrix tablets were formulated employing starch urea and starch urea cross linked with calcium and were evaluated for drug release kinetics and mechanism. Cross-linked starch-urea was more suitable than starch-urea for the design of controlled release tablets of diclofenac. Diclofenac release from the matrix tablets formulated employing cross-linked starchurea was slow and spread over 24 h and depended on percent polymer in the tablets. A good linear relationship was observed between percent polymer in the tablets and release rate. Drug release from the matrix tablets formulated employing cross linked starch –urea was diffusion controlled and followed zero order kinetics. Non – Fickian diffusion was the drug release mechanism from the matrix tablets formulated employing starch-urea and cross linked starch-urea. Diclofenac release from the tablets formulated employing cross linked starch –urea (DF3) gave release over 24 h and similar to that from commercial diclofenac SR tablets. Diclofenac CR tablets for once-a-day (24 h) administration could be designed employing cross-linked starch-urea.