National Repository of Grey Literature 67 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Evaluation of compressibility of acetylsalicylic acid
Pavelková, Petra ; Řehula, Milan (advisor) ; Svačinová, Petra (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Student: Petra Pavelková Consultant: Doc. RNDr. Milan Řehula, CSc. Evaluation of compressibility of acetylsalicylic acid The aim of this thesis was evaluation of stability of acetylsalicylic acid from crystallographic aspect during compression process and to determine compressibility of this medical substance in the same time. For this purpose it was performed measurement of differential scanning calorimetry in range from - 30 žC to 220 žC by a speed of heating 10 žC/min. and cooling - 20 žC/min.. Further, the compaction equation, force-displacement record at compression forces ranging from 5 to 40 kN, and the stress relaxation at compression forces of 5, 10 and 15 kN were used. Measurement took place in specific conditions, which are described below. The experimental results showed following conclusions:  The relation between the parameter E3 and compression force (LS) is non- linear and described by the equation: ESD3 = 0,086 LS + 0,013 LS2 - 0,211 R2 = 0,9999  The relation between plasticity and compression force (LS) is also non-linear and described by the equation: Pl = - 3,603 LS + 0,049 LS2 + 85,506 R2 = 0,9903 Values of the parameter PL show that ASA has a poor compressibility. At a...
Evaluation of compressibility of ibuprofen
Kolarczyková, Barbora ; Řehula, Milan (advisor) ; Svačinová, Petra (referee)
The aim of this study is to determine whether dissociation and a change of crystal modification of ibuprofen do not arise during the compression process. For this purpose an evaluation by means of equation of compression, evaluation by stress relaxation, evaluation by force-distance diagram and evaluation by differential scanning calorimetry is accomplished. The equation of compression developed by department of pharmaceutical technology describes the process of compression by parameters of three phases: phase before compression, phase elastic and plastic deformation. The test of stress relaxation was performed at compression force of 5, 10 and 15 kN. During the evaluation of a force-distance record phase of compression and relaxation of tablet was examined from energetic point of view at compression force of 5, 10, 15, 20, 25, 30, 35, 40 kN. These tablets were also evaluated by means of differential scanning calorimetry. Two basic conclusions arise out of the measured results: during the compression process dissociation or modification of crystal form if ibuprofen and simultaneously low plasticity of medicinal substance was found out (at compression force of 15kN plasticity was only 47 %).
Determination of optimal compression force and speed of compression for the production aciclovir tablets
Vlachová, Hana ; Řehula, Milan (advisor) ; Ondrejček, Pavel (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Student: Vlachová Hana Consultant: Doc. RNDr. Milan Řehula, CSc. Determination of optimal compression forces and speed of compression for the production of aciclovir tablets. This thesis deals with the characterisation of impact compression process on hardness of the tablets. The theoretical part of the thesis describes the effective substance - aciclovir. It also describes compression equations which explain process of compression and factors influencing terminal weight and hardness of tablets. The aim of the experimental part of the work is to measure physical properties of the tablets and find compression forces and speed of compression which are suitable for compression tablets. Tablets were pressed using Kilian Synthesis 700 machine at six compression forces in the range from 4 kN to 14 kN. The height, weight and hardness of each tablet were measured immediately after dressing and note to help for later calculation. The result of the study was to determine the impact of compression forces and compression speed on tablet hardness and weight. Tablet weight decreses with increasing comppession forces. Hardness increases with increasing compression forces. The range of radial hardness...
Evaluation of compressibility of paracetamol
Šorf, Aleš ; Řehula, Milan (advisor) ; Ondrejček, Pavel (referee)
The objective of this work was to evaluate the compressibility of paracetamol by determination of compression and viscoelastic properties of the active substance and also to detect eventual changes in crystal modification of the substance during the compression process. The parameters of the compression equation were determined using tree-exponential equation developed at the Department of pharmaceutical technology. Mutual interactions between particles were also studied by stress relaxation test using compression forces 5, 10 and 15 kN, as well as energetic parameters of a force-distance record using compression forces from 5 to 40 kN. Tablets made in the last mentioned test were used as samples for DSC analysis to seek potential changes in the crystal structure of paracetamol when undergoing the compression process. The evaluation of the executed tests suggested that compression ability of paracetamol in basic form I is very poor and its plasticity when being compressed by commonly used pressures is about 50%, which is considered as very low. It was also found out that any crystal structure changes of the active substance did not occur during compression.
Physico-chemical characteritazion of microcrystalline celluloses
Gregor, Stanislav ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Charles Univerzity in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical technology Student: Mgr. Stanislav Gregor Supervisor: Doc. RNDr. Milan Řehula, CSc. Physico-chemical characteritazion of microcrystalline celluloses Microcrystalline cellulose is very important pharmaceutical excipient. The aim of the study was to evaluate the different types by using physico-chemical charakteristics. Particle size was evaluated by optical microscopy. The flow properties were evaluated by flowability and by the angle of repose. Bulk and tapped properties were evaluated by bulk and tap density and by compressibility index. Temperatute and heat of fusion, glass transitive temperature and specific heat improvers were evaluated by DSC. Compaction process was evaluated by compaction equations, stress relaxation test and record the force-displacement. The compressed tablets were evaluated by kinetics crushing tablets and had fixed radial strength. Particle sizes correspond to the declared values stated by the manufacturer. The largest deviation was found for Avicel PH-200 (difference 20,0 mm). With increasing particle size reduces fiction between particles and increases the flowability. The tapped density is higher than the bulk density and the copies. From the results of three- exponential...
Possibilities for in-vitro testing of controlled-release parenterals.
Kožák, Jan ; Řehula, Milan (advisor) ; Rabišková, Miloslava (referee)
The objective of this study was to start with the development of a gel-based medium simulating intramuscular environment for in-vitro drug release testing as an alternative to currently used water-based media. A pork meat was selected as a model of the muscle tissue. At the first part of the study, diffusion rate was proposed as the most determining factor of drug release in gel-based medium. Consequently, the diffusion rate of sodium fluorescein in pork meat was compared with the diffusion rate in various gels, namely gelatine, calcium alginate and different grades of hydroxypropyl methylcellulose (HPMC). The measurments were performed at 37řC with respect to recomendations for drug dissolution testing and in- vivo temperature. Gelatine however underwent a gel-sol transition at 37řC regardless to polymer concentration and showed to be unsuitable for measurement by selected method. The diffusion rate of fluorescein in all used gels was higher than the diffusion rate in the meat. Only 25% HPMC (Methocel E4M grade) showed acceptable similarity to meat, in terms of the diffusion rate, and was consequently selected for the second part of the study. In the second part of the study, the release of ibuprofen from ethylcellulose implants (ethylcelulose : ibuprofen weight ratio 9:1) in pork meat and 25%...
Effect of paracetamol on the parameters of compression equation
Mařanová, Lucie ; Řehula, Milan (advisor) ; Ondrejček, Pavel (referee)
Evaluation of the tableting mixtures containing the paracetamolum by the parameters of the equation of compression The diploma thesis deals with effect of paracetamol on the parameters of compression equation. These parameters characterize compression process in the individual phases of compression: precompression phase, phase of elastic deformation and phase of plastic deformation. Paracetamolum was studied in the five mixtures, where it occurred in different ratio with microcrystalline cellulose. Looseness, Carr's index and Hausner ratio were evaluated for each mixture. The sizes of reductions ai, sizes of energies Ei and Ri, "half-pressures" pHi and the velocity constants 1/ti were calculated using three-exponential equation of compression for the individual phases of pressing. The results showed poor flow properties of tableting mixtures and thus its unsuitability for direct compression. The results of the study have revealed that increasing amounts of paracetamolum in the mixture increase reduction of volume a1 and velocity of volume change 1/t1 in dependence on the amount of the extruded air and decrease the required energy due to the smooth surface and less friction during the precompression phase. Reduction of volume a2 decrease with the increase of content of paracetamol due to...
Evaluation and optimisation of a granulation process on a laboratory scale fluid bed granulator.
Stoniš, Jan ; Mužíková, Jitka (advisor) ; Řehula, Milan (referee)
The fluid bed granulation is a well-established method how to improve such properties of powders as flowability and increase content uniformity of the tablets. In this thesis, there was evaluated a granulation process on a lab scale fluid Glatt bed granulator and optimized for highest possible yield. Product yield in the size range of 80-90 % of granules and process reproducibility were stated as most effective. The product was analysed for its particle size distribution, the API distribution within the different particle size fractions and the flowability of the final granules. For process optimization, the most critical parameters such as spraying rate, particle size of raw materials and fluid bed pressure were identified and evaluated. As the highest-yielding dosage for the powder binder was found the spraying rate of 9 g/min. Changes in bed fluid pressure and nozzle pressure showed no significant improvement. Different grades of caffeine were compared for their impact on the granulation properties. Sieved caffeine enhanced yield of the product and reproducibility compared to bulk or disagglomerated caffeine.
Validation of a new method for the evaluation of stress relaxation of tablets
Černá, Pavlína ; Řehula, Milan (advisor) ; Svačinová, Petra (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical technology Supervisor: Doc. RNDr. Milan Řehula, CSc. Title of Dissertation: Validation of a new method for the evaluation of stress relaxation of tablets Keywords: tablets, stress relaxation test, elastic and plastic deformation The theoretical part of this thesis deals with the elastic relaxation of tablets. It describes various methods used in the evaluation of elastic recovery of tablets. The present work explores the factors affecting the elastic relaxation of tablets. The experimental part is focused on the stress relaxation test. Until present only one delay was studied. This work studies the stress relaxation after relieving tablet. The parameters A2, T2 and P2 were reviewed. The relationship between the parameters P2 and compression force relief were studied. For experiments microcrystalline cellulose Avicel PH 102 (MCC) was used. Tablets were compressed in a device used for testing the strength of the material in pressure and tension T1-FRO 50. For the determination of the stress relaxation test, the tablets were compressed with 180 sec first delay. The second delay was always 60 sec but it was measured from certain decrease of pressure (7 kN, 6 kN, 5 kN, 4 kN, 3 kN, 2 kN, 1 kN and 0.1 kN). To...
Effect of acetylsalicylic acid on the parameters of compression equation
Šmíd, Jakub ; Řehula, Milan (advisor) ; Ondrejček, Pavel (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Student: Jakub Šmíd Consultant: Doc. RNDr. Milan Řehula, CSc. Effect of acetylsalicylic acid on the parameters of compression equation Compacting process can be expressed mathematically by compression equations. It is characterized by various parameters. The compression equation expresses the dependence of the volume, density and height on compacting pressure. This paper evaluates the parameters of the compaction equation and study pre-loading phase, the phase of elastic deformation and the phase of plastic deformation. This thesis examines effect of acetylsalicylic acid on the parameters of compaction equation. Tablets were compressed from five mixtures. Mixtures contained acetylsalicylic acid and microcrystalline cellulose in different ratios 0:100, 25:75, 50:50, 75:25 and 0:100. The results were obtained using the three-exponential equation. Evaluation was carried out by using box plots.

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