Controlled drug release matrix

Preparation of poly(8-caprolactone) (PCL), a biodegradable polymer that finds applications in the biomedical field for prostheses, bandages, or controlled drug release matrix for active substances, was successfully accomplished by heating the monomer in the presence of nontoxic, biologically acceptable lanthanide halides (SmBrj, SmCl3, YbBrj) as initiators in a scientific microwave unit (Scheme 3.5). PCL with a Af of 14,100 g/mol was obtained after heating at 200 °C for 45 min in the absence of solvent. 

Oral controlled drug-release systems are increasingly used for short half-life drugs to reduce peak blood levels and side-eflfects, to maintain optimum drug concentration and to stimulate patient compliance. In order to maintain a constant blood-level of the drug during an extended period, a constant in vitro drug release rate is desired. The most popular controlled-release system is the matrix tablet (Desai et al., 1965). Te Wierik et al. (1996) reported on... 

Langoth et al. [86] studied the properties of matrix-based tablets containing the novel pentapeptide leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) that has been shown to have pain-modulating properties. The matrix-based tablets were made with the thiolated polymer PCP. The covalent attachment of cysteine to the anionic polymer PCP leads to an improvement of the stability of matrix tablets, enhances the mucoadhesive properties, and increases the inhibitory potency of PCP towards buccal enzymes. All these factors lead to stability of the peptide and a controlled drug release for the peptide was obtained for more than 24 h. Also, the tablets based on thiolated PCP remained attached on freshly excised porcine mucosa 1.8 times longer than the corresponding unmodified polymer. 

Matrix degradation for controlled drug release (A) bulk erosion of a matrix, (B) surface erosion of a matrix. Source. From Ref. 34. 

Analysis of controlled drug release from a matrix [77]... 

Leuenberger, H., J. D. Bonny, and M. Kolb. 1995. Percolation effects in matrix-type controlled drug release systems. Int. J. Pharmaceut. 115 217-224. 

Figure 9.6 Schematic of matrix-type systems for controlled drug delivery. Matrix delivery systems can be constructed with drug dissolved in the matrix material (a) or particles of drug dispersed to form a composite material (b and c). For dispersed drug particles, the overall loading is an important determinant of the dynamics of release.

O-carboxymethy Ichitosan is also used to develop a water-soluble matrix polymer for controlled drug release. OCM-chitosan microspheres containing antibiotic drug pazufloxacin mesilate were prepared by the emulsion method and successively crosslinked with glutaraldehyde [52]. 

Figure 18.17 Erosion controlled drug release from polymer matrix.

---