Formulation and Evaluation of Bilayer Tablets Containing Immediate Release Aspirin Layer and Floating Clopidogrel Layer
Aspirin and clopidogrel are considered the most important oral platelets aggregation inhibitors. So it is widely used for treatment and prophylaxis of cardiovascular and peripheral vascular diseases related to platelets aggregation .In this study aspirin and clopidogrel were formulated together as floating bilayer tablet system. Three different formulas of 75 mg aspirin were prepared by wet granulation method as immediate release layer; different disintegrants used to achieve rapid disintegration. Formula with crosscarmellose as disintegrant achieve rapid disintegration was selected for preparation of bilayer tablet.
Different formulas of 75 mg clopidogrel were prepared as sustained release floating layer by wet granulation (effervescent ) method ;the physical and floating properties for compressed clopidogrel matrix were studied in addition to study the effect of polymer concentration(HPMC) ,and its combination with ethyl cellulose and carbapol ,effect of different diluents and effect of increasing sodium bicarbonate amount on the release from compressed matrix .
Formula prepared with HPMC and EC in a ratio of 1:1 was capable to retard the release of clopidogrel for 6 hours in addition to its good floating behavior and therefore selected to prepare bilayer tablets in combination with selected aspirin layer.
The prepared bilayer tablets were further subjected to evaluation of their physical, floating properties and release behavior. Finally the kinetic study reflects acceptable shelf life for aspirin and clopidogrel.
Key words: Aspirin, Clopidogrel, Bilayer tablet, Floating tablet.