Evaluation of viscoelastic properties of four pharmaceutical fillers of different chemical structure using a stress relaxation test is described. The obtained values express not only the elasticity and plasticity of the material, but also describe the processes inside the compressed material. For each of the fillers tested, three modules of elasticity and three modules of plasticity were calculated. Different modules were found in the polymeric and crystalline fillers. Dehydrated dicalcium phosphate possesses a high module of plasticity comparable to that of microcrystalline cellulose. The strength of dicalcium phosphate tablets is very low in comparison to those from microcrystalline cellulose.
In developing new formulations of pellets it is necessary to start from mathematical models of the process. The Heckel equation employed in practice determines the range of pressures at which plastic deformation of the pellet material takes place. A biexponential equation characterizing the pre-pressing and plastic-deformation stages was designed for pelletizing ceramic materials, which, however, cannot be used for polymeric fillers employed in the manufacture of drug pellets. A three-exponential equation was proposed for the evaluation of the fillers. This equation characterizes the process by three concurrent stages, the reduction of interparticular pores, reduction of intraparticular pores, and reduction of the nonporous solid substance. The stages are evaluated by volume characteristics, the energy needed for the reduction, and further by the pressing pressure under which the 50-% reduction takes place. Using this equation, three polymeric fillers, powdered cellulose, microcrystalline cellulose and (hydroxypropyl)methylcellulose, were evaluated. It was found that microcrystalline cellulose consumes the lowest amount of energy for volume reduction and exhibits the best pressing properties. The worst properties in pressing were found for (hydroxypropyl)methylcellulose. The behaviour of the fillers is substantially influenced by their chemical structure.
Při formulaci tablet je potřebné vycházet z viskoelastických parametrů použitých pomocných látek. Na jejich plasticitu a elasticitu má vliv typ vazeb formulujících se během lisovacího procesu. V této práci jsou hodnoceny viskoelastické vlastnosti vybraných plniv, určených pro přímé lisování tablet. Stanovení byly podrobeny prášková celulosa Vitacel A 300, mikrokrystalické celulosy Avicel PH 101, Avicel PH 102, Avicel PH 103, Avicel PH 200, Avicel PH 301 a Ceolus KG 802. Elasticita plniv byla hodnocena pomocí Youngova modulu pružnosti a diferenční elastické potenciální energie. Plasticita byla hodnocena pomocí relaxace napětí za použití trojexponenciální rovnice podle Maxwellova modelu. Tato metoda byla doplněna o nový originální parametr označený jako celková plasticita PT. V práci byl sledován vliv velikosti částic plniv, hustoty, obsahu vlhkosti a molekulové hmotnosti na elasticitu a plasticitu celulos. Z výsledků práce vyplynulo, že velikost částic celulos neměla vliv na elasticitu a plasticitu plniv. Se vzrůstem hustoty celulos se elasticita zvyšovala a současně plasticita snižovala. Na uvedené viskoelastické parametry měl vliv obsah vlhkosti v plnivech. Se vzrůstem množství vlhkosti v plnivech se elasticita snižovala a plasticita zvyšovala. Se zvyšováním molekulové hmotnosti celulosy se elasticita snižovala a plasticita zvyšovala.
In tablet formulation it is necessary to start from viscoelastic parameters of the excipients employed. Plasticity and elasticity of excipients are influenced by the type of bonds which are being formed in the course of the compaction process. The present paper evaluates the viscoelastic properties of selected fillers intended for direct compaction of tablets. The determinations included cellulose powder, microcrystalline celluloses Avicel PH 101, Avicel PH 102, Avicel PH 103, Avicel PH 200, Avicel PH 301, and Ceolus KG 802. Elasticity of the excipients was evaluated by means of Young’s modulus of elasticity and differential elastic potential energy. Plasticity was evaluated by means of the stress relaxation test using the three-exponential equation following Maxwell’s model. The method was supplemented with a novel original parameter, total plasticity PT. The study examined the effect of particle size of fillers, density, moisture content, and molecular weight on elasticity and plasticity of celluloses. The results of the paper revealed that particle size of celluloses did not influence elasticity and plasticity of excipients. With increasing density of celluloses, elasticity was increased and at the same time plasticity was decreased. The above-mentioned viscoelastic parameters were influenced by the content of moisture in fillers. With increasing amount of moisture in fillers, elasticity was decreased and plasticity increased. With increasing molecular weight of cellulose, elasticity was decreased and plasticity increased.
- MeSH
- celulosa farmakologie terapeutické užití MeSH
- farmaceutická technologie metody MeSH
- farmaceutické pomocné látky farmakologie terapeutické užití MeSH
- farmaceutický průmysl MeSH
- financování organizované MeSH
- léčivé přípravky MeSH
- lidé MeSH
- pružnost MeSH
- tablety farmakologie MeSH
- teoretické modely MeSH
- viskozita MeSH
- Check Tag
- lidé MeSH
- MeSH
- antialergika terapeutické užití MeSH
- antiarytmika terapeutické užití MeSH
- antibakteriální látky terapeutické užití MeSH
- antiflogistika terapeutické užití MeSH
- antioxidancia MeSH
- antivirové látky terapeutické užití MeSH
- cytostatické látky terapeutické užití MeSH
- flavonoidy * dějiny chemie terapeutické užití MeSH
- inhibitory ACE terapeutické užití MeSH
- kardiovaskulární systém * účinky léků MeSH
- lidé MeSH
- myokard * enzymologie imunologie metabolismus MeSH
- systém (enzymů) cytochromů P-450 účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
