Browsing by Subject "Drugs--Coatings"
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Item An investigation of formulation factors and processing parameters for the powder-coating of tablets(2008-05) Sauer, Dorothea, 1979-; McGinity, James W.Dry powder coating of pharmaceutical dosage forms has been investigated as an alternative method to commonly used liquid based coating techniques. Eudragit[trademark] L 100-55 and Eudragit[trademark] L 30 D-55 have been employed in enteric film coatings using aqueous dispersions, organic solutions and compression coating. However, the copolymer has not been investigated in dry powder coating applications. Initially, formulation factors and processing parameters were investigated for the dry powder coating of chlorpheniramine maleate tablets using Eudragit[trademark] L 100-55 as the delayed release polymer. Powder coating was studied as a method to prevent the migration of an ionizable, highly water soluble model drug into the polymeric film during the coating process. Eudragit[trademark] L 100-55 was pre-plasticized with triethyl citrate (TEC) using hot-melt extrusion and subsequently ground into a fine powder. Polyethylene glycol 3350 (PEG 3350) was used as a primer and low melting coating excipient to enhance coating powder adhesion and to improve film formation. The powder coating process was performed in a modified laboratory scale spheronizer. For the dry-powder coating of sodium valproate tablets different subcoating materials were investigated to improve powder adhesion to the substrate and to reduce the level of Eudragit[trademark] L 100-55 required for gastric resistance. PEG 3350 and Methocel[trademark] K4M were incorporated in the Eudragit[trademark] E PO and Eudragit[trademark] RL PO subcoating formulations as pore forming materials. The miscibility of the PEG 3350 and Methocel[trademark] K4M in the film coating was correlated with their ability to function as pore forming agent. The film formation process of thermally cured Eudragit[trademark] L 100-55 dry-powder coatings was characterized. The influence of film additives on relative melt viscosity, surface free energy of the polymer and the mechanical properties of powder-cast films was studied. The influence of Eudragit[trademark] E PO in Eudragit[trademark] L 100-55 film coatings applied by a dry powder coating technique on the drug release mechanism was investigated. Calculation of the Flory-Huggins interaction parameter based on solubility parameters and different analytical techniques demonstrated immiscibility of the copolymers at processing conditions. A broad range of pH dependent theophylline release profiles were obtained as a function of the polymer blend ratio.Item Physical and chemical properties of acrylic polymers influencing physical aging(2007-12) Kucera, Shawn Anthony, 1974-; McGinity, James W.The influence of water soluble and insoluble stabilizing excipients on the physical stability of coated dosage forms was investigated in this study. The effect of the excipients on the thermal and physico-mechanical properties, and water vapor permeability of free films was studied, as was the influence of these excipients on the physical stability and release kinetics of coated pellets. The effect of water-soluble proteins, bovine serum albumin (BSA) and Type B gelatin, on the physical aging of Eudragit[trademark] RS/RL 30 D films was investigated. It was found that ionic interactions occurred above the isoelectric point of BSA and caused unstable films which showed accelerated decreases in drug release rate. The adjustment of the pH of the dispersion below the isoelectric point of BSA resulted in electrostatic repulsive charges that stabilized the drug release rate from coated dosage forms at both ambient and accelerated conditions. The addition of gelatin to the coating dispersion increased the drug release rate due to the formation of gel-domains through which the drug was able to easily diffuse. The influence of silicon dioxide on the stability of Eudragit[trademark] RS/RL 30 D films was investigated. Colloidal grades showed enhanced incorporation in the acrylic matrix; however, unstable films were formed. The addition of silicon dioxide with a larger particle size increased the permeability of the film and stabilization in drug release rate was attributed to constant water vapor permeability values of free films. The influence of ethylcellulose on the physical aging of Eudragit[trademark] NE 30 D coated pellets was studied. The two polymers were found to be substantially immiscible and the drug release rate of coated pellets was constant at both ambient and accelerated conditions which correlated to stabilizations in both the physico-mechanical properties and water vapor permeability of free films. Blending both Eudragit[trademark] NE 30 D and RS 30 D resulted in the formation of coherent films without the need of plasticizer. The two polymers were found to be miscible and both films and coated dosage forms were stable when stored below the glass transition temperature of the polymer blend. When films were stored above this temperature, instabilities occurred as a result of the further coalescence and densification of the polymer blend.Item Recrystallization of guaifenesin from hot-melt extrudates containing Acryl-EZE® or Eudragit® L100-55(2008-05) Bruce, Caroline Dietzsch, 1976-; McGinity, James W.The physical stability of guaifenesin in melt-extruded acrylic matrix tablets was investigated. The initial study found that recrystallization was caused by guaifenesin supersaturation in Eudragit[Trademark] L100-55, and that the instability was confined to tablet surfaces. Drug release was not affected by crystal growth as guaifenesin is very water soluble. The addition of a polymer in which guaifenesin showed a higher solubility to the matrix blend decreased recrystallization on storage as supersaturation levels dropped. The second investigation identified heterogeneous nucleation as an additional factor in guaifenesin recrystallization. A quantitative assay showed that talc in matrix tablets accelerated the onset and extent of the recrystallization due to a nucleating effect on guaifenesin. Storage under elevated humidity conditions promoted recrystallization as well, but crystal growth was not correlated with water uptake, which implied a nucleating effect of moisture on guaifenesin. The third study investigated the effect of aqueous film-coating of the matrix tablets to stabilize amorphous guaifenesin using either hypromellose or ethylcellulose as coating polymers. The selection of the coating polymer influenced crystal morphology, and was a major factor in delaying the onset of crystallization, ranging from 1-3 weeks (ethylcellulose film-coatings) to 3-6 months (hypromellose film-coatings). Higher weight gains retarded recrystallization. Factors promoting drug and polymer diffusion, such as long curing times and elevated temperatures during both curing and storage, incomplete film coalescence and high core drug concentrations all resulted in an earlier onset of crystallization. The effects of single-screw extrusion (SSE) and twin-screw extrusion (TSE) of diltiazem hydrochloride and guaifenesin-containing blends in Eudragit[Trademark] L100-55 on drug morphology and dispersion were studied in the fourth project. Guaifenesin solubilized diltiazem hydrochloride, and plasticized Eudragit[Trademark] L100-55. Extrusion temperature influenced the drug morphology in single-screw extrudates, while TSE rendered all formulations amorphous due to higher dispersive mixing capabilities. Drug distribution improved with extrusion temperature and by TSE over SSE. Homogeneous matrices showed the slowest drug release at pH 1.0. Recrystallization was inversely correlated to drug distribution. In conclusion, the physical stability of guaifenesin in hot melt-extruded acrylic matrix tablets was shown to be affected by formulation, processing and post-processing factors.