Use of microspheres

A parenteral, depot antipsychotic is one that can be administered in such a way that, after a single dose, a therapeutically efficient tissue concentration of at least 1 week s duration is achieved (251,252). Slow release of the active drug is produced by combining the base antipsychotic with a fatty acid (decanoic acid). The alcohol group of the antipsychotic is esterified by the acid, producing a lipophilic compound whose solubility in oil is increased. An oil, usually sesame, is then used as a vehicle for intramuscular injection, where the ester, which is not pharmacologically active, is hydrolyzed by tissue esterases, slowly releasing the active compound. An alternative technique is the use of microspheres (e.g., risperidone). 

The nasal application of drugs is an area of growing interest (21) and a number of publications has shown that simple molecules as well as more complex species (eg calcitonin, insulin etc) can be well absorbed by this route, either directly or in the presence of so-called absorption enhancers. One problem with such materials could be too rapid clearance of the delivery system from the nasal cavity through the efficient action of the mucociliary system. For this reason Ilium has considered the use of microsphere systems. 

FCC use of microspheres with the exception of units (TCC) still using millimeter sized spheres. 

The potential use of microspheres in the pharmaceutical industry has been considered since the 1960s for the following applications ... 

Catalytic oxidation of naphthalene to phthalic anhydride is the seccxid application of FCB which was initiated in 1945. Riley (R12) reported problems on afterburning and on the control of bed temperature, and introduced many improvements in the fluidized bed. However, the most important change to make scale-up easier and to achieve good performance was the use of microspherical catalyst, or moderately active German-type catalyst (Bll, G14). 

The efficacy of RA in PVR has been evaluated in animal models. A single intravitreal injection of RA used in conjunction with silicone oil reduces the incidence of traction retinal detachment (40). Use of microsphere encapsulation of RA to prolong the intravitreal half-life reduced the incidence of PVR in the rabbit model by 64% (41). Intravitreal RA suspended in 1% sodium hyaluronate has also been studied in a rabbit model of PVR and has similar inhibitory effect on PVR progression. The authors suggested that in cases in which silicone oil was not necessary, sodium hyaluronate could be used as an RA vehicle, though transient elevations of intraocular pressure could be expected (42). 

Studying the use of microspheres encapsulated with glucose oxidase (GOX) for MDR cancer treatment [115], We found that cancer cells can be extensively killed by the reactive oxidative species generated by the encapsulated GOX enzyme. The most appealing feature of this therapy is that the GOX-mediated cytotoxic effect is essentially unaffected by the MDR phenotype (Fig. 4). Further studies will be conducted to optimize this strategy. 

Barrow EL, Winchester GA, Staas JK, Quenelle DC, Barrow WW. Use of microsphere technology for targeted delivery of rifampin to Mycobacterium tuberculosis-infected macrophages. Antimicrobial Agents and Chemotherapy. October 1998 42(10) 2682-2689. PubMed PMID 9756777. Pubmed Central PMCID 105919. 

Relatively stable gels were formed for matrices loaded with approximately 6 mM whether provided by microspheres only in vitro or by a combination of ions from the reservoir microspheres and surrounding tissue fluid in vivo. Cellular inflltration of the gels was supported by the macroporous morphology of gels formed in sim following injection. The ability to incorporate soluble immunomodulatory factors like interleukin-2 (IL-2) directly into the matrix and the use of microspheres as modular components for slow release CpG oligonucleotides electrostatic anchored to the surface may provide a potent platform for immunotherapy when combined with delivery of immime cells [146]. 

The use of microspheres in hepatic arterial embolization demonstrates promise in dealing with neuroendocrine tumors with a high degree of effectiveness at low toxicity. Further studies are warranted to demonstrate its effectiveness in other treatment schemas. 

Inverse suspension polymerisation is a convenient way to obtain microspheres of hydrophilic polymers. More details about the use of microspheres for therapeutic embolisation are found in Section 4.3.8. 

Filters can be used, but the use of filter results in a waste of expensive drug materials. Therefore, several methods that allow better control over particle size and size distribution have been proposed. Each of these methods has drawbacks that prevent the use of microspheres in various applications. 

Rand T, Loewe C, et al. (2005) Arterial embolization of unresectable hepatocellular carcinoma with use of microspheres, lipiodol, and cyanoacrylate. Cardiovasc Intervent Radiol 28 313-318... 

One promising approach is to encapsulate signalling molecules, such as therapeutic growth factors or drugs in microspheres, which are then incorporated into biphasic scaffolds. The use of microspheres is versatile because they can be utilized as a scaffold as well as a delivery vehicle (Seo, Mahapatra, Singh, Knowles, Kim, 2014). 

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