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      Optimization of experimental parameters for the production of LMWH-loaded polymeric microspheres

      ,

      Drug design, development and therapy

      Dove Medical Press

      spray drying, LMWH, DOE, fractal, microspheres

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          Abstract

          The present study reports on the production of low molecular weight heparin (LMWH) loaded polymeric microspheres for delivery via the oral route. The microspheres were prepared by the spray-drying technique using Eudragit ® as the polymer. The objective of this study was to examine extensively the influence of formulation and process variables on the characteristics of the microspheres prepared. The effects of various experimental parameters such as polymer concentration, inlet temperature, and liquid feed flow rate on particle morphology, particle dimensions, and production yields were evaluated by means of experimental factorial designs. Electron microscopy, moisture content analysis, and fractal dimensional analysis were employed to characterize the microspheres. The inlet temperature and polymer concentration had the greatest effects on the production yield. Results showed that the polymer concentration affected the dimensions of the microspheres. Drug-loaded microspheres were spherical in shape and had a smooth surface with sizes ranging between 19–60 μm. Production yields were above 50% under most of the operating parameters studied. The selection of appropriate parameters yielded spray-dried microparticles characterized by smooth morphology and narrow dimensional distribution.

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          Most cited references 17

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          Effects of a low-molecular-weight heparin on thrombus regression and recurrent thromboembolism in patients with deep-vein thrombosis.

           R. Nakov,  ,  V Hach-Wunderle (2001)
          Low-molecular-weight heparins are frequently used to treat venous thromboembolism, but optimal dosing regimens and clinical outcomes need further definition. In this multicenter, open-label study with blinded adjudication of end points, we randomly assigned patients with acute deep-vein thrombosis to one of three treatment regimens: intravenous administration of unfractionated heparin; subcutaneous administration of a low-molecular-weight heparin, reviparin, twice a day for one week; or subcutaneous administration of reviparin once a day for four weeks. The primary end point was evidence of regression of the thrombus on venography on day 21; secondary end points were recurrent venous thromboembolism, major bleeding within 90 days after enrollment, and death. Of the patients receiving unfractionated heparin, 40.2 percent (129 of 321) had thrombus regression, as compared with 53.4 percent (175 of 328) of patients receiving reviparin twice daily and 53.5 percent (167 of 312) of the patients receiving reviparin once daily. With regard to thrombus regression, reviparin administered twice daily was significantly more effective than unfractionated heparin (relative likelihood of thrombus regression, 1.28; 97.5 percent confidence interval, 1.08 to 1.52), as was reviparin administered once daily (relative likelihood, 1.29; 97.5 percent confidence interval, 1.08 to 1.53). Mortality and the frequency of episodes of major bleeding were similar in the three groups. In acute deep-vein thrombosis, reviparin regimens are more effective than unfractionated heparin in reducing the size of the thrombus. Reviparin is also more effective than unfractionated heparin for the prevention of recurrent thromboembolism and equally safe.
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            Production of Eudragit microparticles by spray-drying technique: influence of experimental parameters on morphological and dimensional characteristics.

            The aim of this study was to evaluate the influence of operating parameters on the characteristics of methacrylate microparticles prepared by spray-drying technique. Eudragit microparticles were prepared by a spray-drying method. The influence of different experimental parameters (i.e., solvent, feed rate, air flow rate, air-drying temperature, and aspiration flow rate) on microparticle morphology, size distribution, and recovery was studied. In addition, different Eudragit types and Eudragit RS concentrations were employed. Optical and electron microscopy were employed to analyze microparticle morphology and dimensional distribution. Finally, prednisolone as model drug was encapsulated in Eudragit RS microparticles. Low feed rate values yielded the best results in terms of microparticle morphology. Changes in nebulizing air flow did not result in a corresponding effect on microparticle characteristics. An increase of air-drying temperature resulted in a reduction of microparticle dimension and recovery. A low flow of drying air was preferable because this resulted in microparticles with an optimal morphology. The polymer concentration affected both morphology and dimensions of microparticles. The encapsulation of prednisolone led to good incorporation efficiencies without altering percentage of recovery, morphology, and mean dimension of the microparticles. The selection of appropriate parameters yielded spray-dried Eudragit RS microparticles characterized by good morphology and narrow dimensional distribution.
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              Bovine serum albumin loaded poly(lactide-co-glycolide) microspheres: the influence of polymer purity on particle characteristics.

              To study the influence of polymer purity on microsphere characteristics, bovine serum albumin (BSA) loaded biodegradable microspheres were prepared by spray drying using two samples of poly(lactide-co-glycolide), PLG, (50:50, mwt = 35 and 69 kDa). Polymer properties were varied by DL-lactide and glycolide addition or by ultrafiltration. While the effective drug loading was not affected by polymer purity, Tg was decreased with increasing monomer and oligomer content. The removal of these low molecular weight substances by ultrafiltration led to a narrower molecular weight distribution compared to the untreated PLG. Concerning the polymer with the higher molecular weight, microsphere morphology was also strongly affected by polymer composition. In contrast to the non-modified PLG, monomer addition yielded particles with a much smoother surface structure. Moreover, in vitro cytotoxicity of the microspheres prepared from the polymer pretreated by ultrafiltration was significantly reduced, whereas monomer addition caused a dramatic decrease of cells surviving contact with the microsphere extract. The in vivo degradation rate of the ultrafiltered microspheres was decreased and as a result, protein release at later times was slowed down. Furthermore, depending on the effective drug loading level, monomer addition resulted in a decrease in the initial protein burst. It can be concluded that the effect of low molecular weight impurities in a polymer on microsphere characteristics and on cytotoxicity cannot be ignored. Their elimination is possible by ultrafiltration.
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                Author and article information

                Journal
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                Drug design, development and therapy
                Dove Medical Press
                1177-8881
                2008
                6 February 2009
                : 2
                : 39-47
                Affiliations
                Butler University, College of Pharmacy and Health Sciences, Indianapolis, IN, USA
                Author notes
                Correspondence: Nusrat Motlekar Assistant Professor, Butler University, College of Pharmacy and Health Sciences, Indianapolis, IN, USA Tel +1 317 940 6427 Fax +1 317 940 3046 Email nmotleka@ 123456butler.edu
                Article
                dddt-2-39
                2761187
                19920892
                © 2008 Motlekar and Youan, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.
                Categories
                Original Research

                Pharmacology & Pharmaceutical medicine

                doe, microspheres, spray drying, fractal, lmwh

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