Formulation and Evaluation of Antihypertensive Microparticulate Drug Delivery System

The phenomenon of absorption via a limited part of the GI tract has been termed the "narrow absorption window", once the dosage form passes the absorption window, the drug will be neither bioavailable nor effective. In extreme cases, drugs, e.g. methyldopa, Captopril, that are insufficiently absorbed due to narrow absorption cannot be delivered entirely, and are either given by a parentral route, or the development of such medication, which is otherwise safe and effective, is stopped altogether. Diltiazem HCL is a calcium channel blocker widely used for the treatment of angina pectoris, arrhythmias and hypertension. Its short biological half life and thus frequent administration (usually three to four times a day) makes it a potential candidate for CR: SR preparations. It has a short plasma half life of about 3 hours. Diltiazem HCL microspheres were prepared by chemical cross linking method. The microspheres were spherical, discrete and free-flowing. Encapsulation efficiency was found to be 95.62 %. Diltiazem HCL release from microspheres was slow and diffusion controlled. Good liner relationships were observed between percent coat and release rate of the microspheres.