Drug delivery systems polymer spheres

Fig. 3 Release of drug from various shapes of pol5mer membrane permeation-controlled drug-delivery systems (A) sphere-type, (B) cylinder-type, and (C) sheet-type. In (D), the drug concentration gradients across the rate-controlling polymeric membrane and hydrodynamic diffusion layer exist in series. Both the polymer membrane, which is either porous or non-porous, and the diffusion layer have a controlled thickness and h, respectively).

Zhao L, Wei YM, Yu Y, Zheng WW. Polymer blends used to prepare nifedipine loaded hollow micro-spheres for a floating-type oral drug delivery system In vitro evaluation. Archives of Pharmacal Research. March 2010 33(3) 443-450. PubMed PMID 20361310. 

Controlled release drug delivery systems are used to deliver the drug locally or system cally at a predetermined rate for a specified period of time [55-57], These systems are used to provide desirable delivery profiles that can achieve therapeutic plasma levels [58,59,55]. In these systems, the drug release is dependent on polymer properties, thus the application of these properties can produce well-characterized and reproducible dosage forms [60]. This section will focus on the two major types of systems micro-spheres/nanoparticles and tablets. 

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