Microcapsules drug release from

Lawter, J. R., Brizzolara, N. S., Lanzilotti, M. G., and Morton, G. O., Drug release from poly(glycolide-co-lactide) microcapsules, Proc. Int. Symp. Control. Rel. Bioact. Mater., 14,... 

Tirkkonen, S. and Paronen, P. (1992) Enhancement of drug release from ethylcellulose microcapsules using solid sodium chloride in the wall. International Journal of Pharmaceutics, 88, 39-51. 

Kader A, Jalil R. Formulation factors affecting drug release from poly(lactic acid)(PLA) microcapsule tablets. Drug Dev Ind Phann 1999 25(2) 141 151. 

Each of these can be related to the manufacture and rate of drug release from the systems. The following discussion presents methods of manufacture of coated or encapsulated systems, referred to as microcapsules, and matrix systems containing homogeneously distributed drug, referred to as micromatrices. 

Takenaka H, Kawashima Y, Lin SY. Preparation of enteric-coated microcapsules for tableting by spray-drying technique and in vitro simulation of drug release from the tablet in GI tract. ] Pharm Sci 1980 69 1388-1392. 

Sodium chloride has been used as a lubricant and diluent in capsules and direct-compression tablet formulations in the past, although this practice is no longer common. Sodium chloride has also been used as a channeling agent and as an osmotic agent in the cores of controlled-release tablets. It has been used as a porosity modifier in tablet coatings,and to control drug release from microcapsules. 

Another medical appUcalion of biopolymer-based microcapsules was reported by Hui et al. (2013). It was shown that a cotton fabric with embedded chitosan-sodium alginate (CSA) microcapsules loaded with traditional Chinese herbs, PentaHerbs, could be potentially used in the treatment of atopic dermatitis. The active ingredient used was gallic acid. The drug release from the chitosan-sodium alginate microcapsule was tested in vitro, under two simulated human skin conditions, in phosphate buffer saline (PBS) of pH 5.4 and 5.0. Fig. 5.12 demonstrates the fast release of gallic acid... 

Chloropromazine (8—34 wt% loading) has been microencapsulated in PCL-cellulose propionate blends by the emulsion solvent evaporation method (61). Phase separation for some ratios of the two polymers was detectable by SEM. The release rate from microcapsules in the size range of 180-250 pm in vitro (Fig. 11) was directly proportional to the PCL content of the blend, the half-life (50% drug release)... 

In vitro dissolution at increasing pH allows a comparison to be made between the different microcapsules prepared with various core wall ratios. The drug dissolution from the microcapsules depends on the core coat ratio and the rate of drug release decreases with a decrease in core coat ratio. 

The release of the drug phenobarbitone (PB) from tablets prepared using simple mixtures of DL-PLA and PB, as well as from the corresponding tablets from microencapsulated PB, is reported. These results are compared with release from the original microcapsules. 

The release from microcap systems is more complicated. First the drug has to dissolve in dissolution fluid which has diffused into the tablets via pores and then between the plates of poly (DL-lactic acid) forming the walls of the microcapsules. This drug solution then has to diffuse out of the tablet via the same route. The effect of compression on the release has more significance in the simple matrix tablets than the microcap systems, because of the above mechanism of release. Higher compressions reduce the size of the pores between the poly(DL-lactic acid) plates, which extends the release. 

Another approach to reach delayed release from chitosan matrices are ionic interactions with polyanions. The formation of a polyelectrolyte complex membrane prevents early drug release. Via this method microcapsules can be formed between chitosan and alignate or even nanoparticles can be derived upon the complexation of chitosan with the polyanion tripolyphosphate. 

It may be necessary to consider the effect of a boundary layer on the release rate. A boundary layer of appreciable drug concentration on the surface of the device would hinder drug release by diffusion. The effect of the layer is more marked with drugs of low solubility and with microparticles having irregular surfaces. From this simple example, it can be seen that various factors affect the release rate from reservoir microcapsules. 

Gardner, D.L. Patanus, A.J. Fink, D.J. Steroid release from microcapsules. In Drug Delivery Systems Gabelnick, H.L., Ed. DHEW Publ. No. (NIH), 77-1238 Department of Health, Education, and Welfare Washington, 1977 265-278. 

It has been shown that a modified drug release can be obtained from calcium alginate microcapsules, pellets, and microspheres. When biodegradable bone implants composed of calcium alginate spheres and containing gentamicin were introduced into the femur of rats, effective drug levels in bone and soft tissue were obtained for 30 days and 7 days, respectively. ... 

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