Applications as a Pharmaceutical Excipient

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. 

Owing to the hydrophilic nature of chitosan, this compound has been used directly as compressible diluent in tablets. Chitosan has excellent properties as excipient for direct compression of tablets, where the addition of 50% chitosan results in rapid disintegration. The DD determines the extent of moisture absorption. Also, in immediate-release formulations, e.g., as a disintegrant in small amounts, where it has been found to have effects similar to or better than those of microcrystalline cellulose. Chitosan at concentrations higher than 5% is a better disintegrate than corn starch and microcrystalline cellulose, depending on chitosan crystallinity, DD, MW and particle size [61]. In addition, it has excellent tablet binder properties compared to other excipients [62]. 

In a different perspective, chitosan-anionic polymers-based extended-release tablets were developed and the feasibility of using this system for the sustained release of highly water-soluble drugs with high drug loading was tested. Here, sodium valproate and valproic acid combined were chosen as the model drugs. Anionic polymers such as 

In Table 9.3 are depicted recent examples of the most explored drug systems in the form of microspheres and nanoparticles using chitosan and derivatives in their formulation. 

Doxycycline-loaded chitosan microspheres were developed using a novel water-inoil emulsion technique, involving oil phase ionic gelation. Assessment of antibacterial activity showed that doxycycline was able to exhibit a minimum microbicidal concentration (MIC) of 16.5,17.4,11.2 and 98.3 pg a gdinst Klebsiella pneumoniae (ATCC 15380), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 9144) and Pseudomonas aeruginosa (ATCC 25619), respectively. The scope of this investigation was the use of doxycycline-loaded chitosan microspheres for healing infected wounds [86]. 

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