Graft copolymers of ethyl methacrylate on waxy maize starch derivatives as novel excipients for matrix tablets: physicochemical and technological characterisation. Eur J Pharm Biopharm
Departamento Farmacia y Tecnología Farmacéutica, Universidad de Sevilla, Sevilla, Spain.European journal of pharmaceutics and biopharmaceutics: official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V (Impact Factor: 3.38). 05/2009; 72(1):138-47. DOI: 10.1016/j.ejpb.2008.12.008
Nowadays, graft copolymers are being used as an interesting option when developing a direct compression excipient for controlled release matrix tablets. New graft copolymers of ethyl methacrylate (EMA) on waxy maize starch (MS) and hydroxypropylstarch (MHS) were synthesised by free radical polymerization and alternatively dried in a vacuum oven (OD) or freeze-dried (FD). This paper evaluates the performance of these new macromolecules and discusses the effect of the carbohydrate nature and drying process on their physicochemical and technological properties. Grafting of EMA on the carbohydrate backbone was confirmed by IR and NMR spectroscopy, and the grafting yields revealed that graft copolymers present mainly a hydrophobic character. The graft copolymerization also leads to more amorphous materials with larger particle size and lower apparent density and water content than carbohydrates (MS, MHS). All the products show a lack of flow, except MHSEMA derivatives. MSEMA copolymers underwent much plastic flow and less elastic recovery than MHSEMA copolymers. Concerning the effect of drying method, FD derivatives were characterised by higher plastic deformation and less elasticity than OD derivatives. Tablets obtained from graft copolymers showed higher crushing strength and disintegration time than tablets obtained from raw starches. This behaviour suggests that these copolymers could be used as excipients in matrix tablets obtained by direct compression and with a potential use in controlled release.
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ABSTRACT: In last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluates the physicochemical and mechanical properties of new graft copolymers of ethyl methacrylate (EMA) on tapioca starch (TS) and hydroxypropylstarch (THS), synthesized by free radical polymerization and dried in a vacuum oven (OD) or freeze–dried (FD). Infrared and 13C NMR spectroscopies confirm the change of chemical structure of the copolymers and X-ray diffraction shows up the higher amorphization of copolymers respect to the carbohydrates. Particle size analysis and SEM indicate that graft copolymerization leads to an increase of particle size and a more irregular shape. Graft copolymerization implies decrease of density and moisture content values. Heckel equation shows that copolymers have less densification by particle rearrangement and fragmentation than carbohydrates. Concerning the drying methods, FD products have larger plasticity and lower elasticity than OD copolymers. Graft copolymerization produces a decrease of the applied pressure necessary to obtain tablets, ejection force and friction work. Furthermore, graft copolymers show longer disintegration time than tablets from raw starches. These qualities suggest that these copolymers could be used as excipients in matrix tablets obtained by direct compression, and with a potential use in controlled release.European Polymer Journal 06/2009; 45(6-45):1765-1776. DOI:10.1016/j.eurpolymj.2009.02.019 · 3.01 Impact Factor
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ABSTRACT: This paper studies the Riboflavin release from compressed disc modules of Dome Matrix(R) technology using tapioca starch-ethylmethacrylate (TSEMA) and tapioca hydroxypropylstarch-ethylmethacrylate (THSEMA), graft copolymers produced by two different drying methods. The comparison with the release behaviour of similar HPMC modules was performed. Two different shape modules have been made, identified as female and male modules, in order to obtain their assemblage by interlocking the disc bases. HPMC matrices showed quasi-linear Riboflavin release in case of both female and male modules, with faster drug release than TSEMA modules. In the case of THSEMA modules, a faster release was observed compared to HPMC modules. Furthermore, matrices obtained with TSEMA copolymers remained nearly intact after dissolution process, while matrices containing HPMC experimented a complete dissolution of the modules. Combining these results with the release curve analysis using the Korsmeyer and Peppas exponential equation, HPMC modules controlled the drug release by polymer relaxation or erosion. For TSEMA and THSEMA, the drug release mechanism was controlled mainly by drug diffusion. The pronounced faster releases for the matrices containing THSEMA copolymers compared with the ones with TSEMA were due to a more important erosive support; however, the main structure of the matrix remains coherent. Porosity and tortuosity values and the shape of the modules explained the drug release observed.European journal of pharmaceutics and biopharmaceutics: official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V 05/2010; 75(1):42-7. DOI:10.1016/j.ejpb.2010.01.004 · 3.38 Impact Factor
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ABSTRACT: This study is a secondary data analysis of a clinical trial assessing the effectiveness of outreach case management (OCM) in linking discharged methadone patients back into treatment. The original trial assessed the effectiveness of the OCM intervention compared to a passive referral among methadone clients who needed treatment postdischarge but had not reengaged. The purpose of this study was to assess the characteristics and long-term outcomes of all clients who were discharged from methadone maintenance treatment including those who had reengaged in treatment. A total of 230 methadone clients were interviewed 3 months and then again at 9 months following discharge from treatment. Compared with participants who needed treatment but had not reengaged (NoTx: 56%), those who had successfully reenrolled in treatment (Tx; 44%) were more likely to be female, not married, and unemployed; had a longer history of sedative use; reported more psychiatric hospitalizations; and were originally enrolled in a community-based rather than a Veterans Administration program. Despite having more severe problems, the Tx group had fewer opioid-positive urines and reported less IV drug use at 9 months postdischarge compared to the NoTx group. The findings highlight the importance of rapid treatment reengagement.Journal of substance abuse treatment 10/2010; 40(2):165-74. DOI:10.1016/j.jsat.2010.09.007 · 2.90 Impact Factor
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