الفهرس 
General IntroductionOnly 14 pages are availabe for public view
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Abstract
Oral controlledrelease multiunit dosage forms (e.g., pellets, granules or microparticles) are becoming more and more important on the pharmaceutical market, as they provide several advantages compared to singleunit dosage forms (e.g., tablets or capsules). There is an increasing interest in the use of drug delivery systems that consist of controlled release coated microcapsules incorporated into compressed tablets. Metoclopramide HCL and nifedipine were chosen as model drugs for preparation of microencapsules and subsequent direct compression into tablets. In order to achieve the objective of this study, the thesis includes preparation, characterization and coat modification of ethylcellulose microcapsules containing metoclopramide HCL and nifedipine. The prepared microcapsules are then compressed into tablets and the physical characters of both microcapsules and tablets were studied. Also, the stability of certain tablets at different temperatures was investigated. Also, the bioavailability of chosen tablets was conducted and compared to conventional tablets. The obtained results revealed that, increasing polymer ratio retarded the release of metoclopramide HCL from ethylcellulose microcapsules. The use of plasticizers increases the incorporation efficiencies and the yield values. Sealing of the microcapsules with waxy materials is necessary to control the drug release. The release rate of metoclopramide HCL from tableted microcapsules was decreased than that from corresponding microcapsules and the use of internal and external plasticizers and protective agents can protect the microcapsules walls against rupturing by the mechanical pressure applied during tableting. Sealing of the microcapsules walls by waxes produces a controlled release tableted microcapsules of metoclopramide HCL. The percent drug content remained was within the pharmacopeial limits upon storage for 6 months at the tested temperatures and the degradation followed firstorder kinetics. Also the expiration rate was estimated from arrhenius plot and was found to be comparable with that at 25 (R@(BC. Invivo assessment of the metoclopramide HCL tested formulations revealed a delayed drug absorption, lowered peak plasma concentration and maintained higher plasma concentrations for longer time compared to the conventional tablets.