ABSTRACT
The most important consideration when designing an effective delivery system for any drug is that of achieving a predictable and reproducible absorption into systemic circulation with high bioavailability. In the case of PP drugs, an interplay of poor permeability characteristics; luminal, brush border, and cytosolic metabolism; and hepatic clearance mechanisms results in their poor bioavailability from oral and non-oral mucosal routes. Hence, at present these drugs are usually administered by parenteral route. However, inherent short half-lives of PPs and almost warranted long-term therapy requirements in a majority of cases make their repetitive dosing necessary. Frequent injections, oscillating blood drug concentrations, and low patient acceptability make even the simple parenteral administration of these drugs problematic (5).During designing and preparing microspheres and micro-capsule for PPs carriers, the preparation process, drug-loading ways, inner structure, and surface characteristics of microparticles have important influence on drug-loading efficiency, drug activity, and release profile, and these would further affect the delivery, adsorption, and bioavailability of PPs. Therefore, it is necessary to consider all these factors during design and preparation of drug carriers for PPs. 9.3 Characteristics and Advantages of
Microsphere-Based Drug-Delivery SystemsA controlled release drug-delivery system should be able to achieve the following benefits: (i) maintenance of optimum therapeutic drug concentration in the blood with minimum fluctuation; (ii) predictable and reproducible release rates for extended duration; (iii) enhancement of activity duration for short half-life drugs; (iv) elimination of side effects, frequent dosing, and wastage of drug; and (v) optimized therapy and improved patient compliance.
