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Biomedical subjects

István Eros

Publications and source records attributed to István Eros.

14 recordsLinked to original sources
PubMed2006

[Investigation of the structure of macromoleculare gels II: analysis of viscosity curves].

Viscosity curves of gels from homo-and copolymers in aqueous medium reviewed in our previous paper were studied. Viscosity vs. rate of shear, and viscosity vs. shearing time were analysed. The viscosity curves can be described with multiplicative functions and the slope of these functions characterizes the orientation ability of polymer molecule-chains under shear. On the base of viscosity vs. shearing time functions the network formed from polymers can be classified into energetic structure, topologic one and/or friction one. It was also established, that the aqueous polymer network structures studied do not thixotropic systems.

Gels↗
PubMed2005

The effect of the solvent on the film-forming parameters of hydroxypropyl-cellulose.

In pharmaceutical technology, film-forming agents are often applied in solution during the preparation of solid dosage forms. A wide range of polymers have already been examined, but many of the effects of the applied solvent on the properties of the film are still not fully known. The study of these phenomena might be of great help in the preparation of better films. In the present study, the frequently used polymer hydroxypropyl-cellulose was examined in water and ethanol. The latter solvent exhibits better wetting properties for this polymer. It was found that the use of ethanol enhanced the processibility because of the easier atomization and the shorter drying period. Properties characteristic of the chemical nature (wetting, surface free energy and thermal properties) and the physical behaviour (deformation process) of the poured films were studied. Relevant differences were detected only in the mechanical parameters. The sizes of the free volume holes in the differently prepared polymers were also determined, but this parameter proved irrelevant as concerns alterations of the breaking process. The explanation of the differences processibility of the films might be the different strengths of binding between the macromolecular chains. This phenomenon can also explain the different degrees of hydration of the polymer and the changes in the drying process.

Cellulose↗
PubMed2005

[Monitoring the temperature distribution during dielectric drying].

Microwave assisted vacuum drying offers never questioned advantageous and it is getting more and more popular lately. In spite of its uniqueness there is a rightful resistance and mistrust because the temperature distribution of the workload is far from being homogeneous as a result of the existing inhomogeneous electromagnetic field. The aim of this study is to survey the heat thus field distribution in the workload to prevent local overheating that endangers the quality of the pharmaceutical product. Thermography as a non perturbing thermometrical method was used to map the heat distribution in the workload. To get a 3D information Teflon layers were used to form cross-sectional and photogenic surfaces about the dusty blend and a purpose-developed software to evaluate qualitatively the IR pictures.

Electricity↗
PubMed2005

[Investigation of solubility properties of nifluminic acid containing cyclodextrins and polyvidone].

One of the most important task of the pharmaceutical technology is to reach a possible high gastrointestinal absorbtion of the active ingredient. Therefore, it is necessary to have a good solubility in the gastric/intestinal medium. In this way the applied drug quantity and unwanted side effects can be reduced with solubility increasing. The water-insoluble drug's solubility and bioavailability can be increased by the alteration of their physicochemical properties. Nifluminic acid is a frequently used anti-inflammatory drug with low aqueous solubility. Inclusion complexation with cyclodextrins is an efficacious method to improve the solubility, stability and bioavailability. Ternary systems were prepared and investigated to use nifluminic acid, hydoxypropyl-beta-cyclodextrin and polyvidone. The aims of the study were to investigate the solubility rate, the in vitro diffusion ability, to determine the n-octanol/water partition coefficient, and to study the thermoanalitycal properties of products. The results suggested that complexation with cyclodextrin and the use of polyvidone is better method than to prepare binary systems. Inclusion complexation was presumed in the event of the ternary composition to improve the bioavailability of nifluminic acid.

Cyclodextrins↗
PubMed2005

[Surface active agents in drug forms and biological systems].

The application areas of surface active agents in the pharmaceutical technology are surveyed. Three topics are summarized: (i) application of surfactant as traditional additives, (ii) the role of surfactant in modern drug delivery systems, and (iii) biopharmaceutical use of surfactants in different dosage forms. The team dealing with colloid carriers at the Pharmaceutical-Technological Department in Szeged has worked out several relationships in mathematical form. These relationships establish the formulation and give an exact character to it. Exponential functions were found between contact angle of wetting and the consistency parameters of water free coherent ointment-systems. There is an exponential relationship between contact angle and structure solidification of ointments measured during storage, between contact angle and structure-forming constant of coherent emulsions, and between contact angle and activation energy of thermostability. There is a linear relation between the contact angle of wetting and water uptake ability of absorbing ointments. On the investigation of emulsions a relationship was evaluated between the surfactant amount accumulated of the interface of oil and water phase and the viscosity and stability of emulsions. The amount of surfactant accumulated on the interface can determine the formation of multiple emulsions. On the area of solubilization there is a reciprocal relationship between the surface tension of surfactant solution and the solubilized amount of drugs. On the area of drug liberation a relationship characterized with a maximum curve can be described between the concentration of surfactant and the released drug. These functions can help the formulation of compositions having a suitable bioavailability.

Dosage Forms↗
PubMed2005

[Investigation of structure of macromoleculare gels, I. Analysis of flow curves].

Six polymers with different structure were investigated. The polymers studied were as follows: methylcellulose, hydroxyethylcellulose, carboxymethylcellulose sodium, polyacrylate sodium-polyacrylamid copolymer (Hostacerin PN 73), poly(vinylpyrrolidone)-poly(vinylacetate) copolymer (Kollidon VA 64) and poly(ethylenoxide)-poly(propylenoxide) blockpolymer. Physical networks from polymers in aqueous media were prepared. The flow curves of these systems were determined. Polynoms, multiplicative functions and linear ones were fitted to the flow curves. The close packing was characterised by correlation coefficient. Physical content of function constants was delineated. Practically the constants expressing the binding forces has a great importance. It was established, that the binding forces in cellulose derivates gels and that of acrylic acid-acrylamide polymer gels are similar. Other structure binding forces act in the poly(ethylenoxide)-poly(propylenoxide) block-copolymer systems. The difference are well demonstrated by the constants values of functions.

Cellulose↗
PubMed2005

[Preparation and investigation of gemfibrozil + dimethyl-beta-cyclodextrin products and solid dosage forms].

Gemfibrozil is a lipid-regulating active substance. Dimethyl-beta-cyclodextrin products were prepared from this sparingly soluble pharmacon by means of methods such as physical mixing, kneading, spray drying and ultrasonication. Solid dosage forms (hydroxypropylmethyl cellulose /HPMC/ capsules and tablets) were prepared from the selected products on the basis of their dissolution profile and the in vitro membrane diffusion results. This publication details the results of electronmicroscopic morphological studies, particle size analysis and wetting contact angle determinations, and also the preparation and examination of the resulting solid dosage forms.

Diffusion↗
PubMed2005

[Surfactants in dosage forms and biological systems. Part II].

The 2nd parts of publications are summarized the modern drug delivery systems contained surface active agents and the role of surfactants in the formation and stability of drug delivery systems. This paper reviews the structure and stability of multiple emulsions, and the different associates forming from surfactants. The solubilization is characterized and some mathematic functions between surface tension of surfactants and their solubilization capacity are introduced. Surfactants represent as important components of coherent emulsions, different vesicles and liposomes. The tensids have an important biopharmaceutical role. They can influenced the bioavailability by increase of thermodynamic activity of active substance and by change of permeability of cellular membranes.

Dosage Forms↗
PubMed2004

Film coating as a method to enhance the preparation of tablets from dimenhydrinate crystals.

Crystals of dimenhydrinate as a model drug were used for crystal coating, a method that can be applied to increase the flowability of a material and facilitate the tablet making. An increase in particle size was observed during the film coating. The change in shape of the coated particles was also examined. Some physicochemical parameters changed during coating, e.g. the surface free energy parameters and the wetting of the samples. The amount of coating material (and therefore the coating time) influenced several parameters (the shape of the particles, the flow properties and surface free energy parameters, compressibility and compactibility). Several parameters of prepared tablet (porosity, breaking hardness) were examined. Accordingly, coating of the crystals can be performed in order to enhance the handling of a material with insufficient properties for tablet making.

Antiemetics↗
PubMed2004

Surface treatment of indomethacin agglomerates with eudragit.

Indomethacin is a widely used anti-inflammatory drug with serious side-effects. This drug was used as a model drug for the coating of agglomerates with a permeable film (Eudragit NE). The agglomeration of the crystals increased the flowability of the bulk crystals. The coating further improved the flowability, and also the uniformity of the mass of the filled capsules. The coating film also influenced the wetting of the samples. The coating decreased the surface free energy and therefore reduced the adhesion forces between both the dry and the wet particles. The modification of the flow properties and the even capsule filling can be explained by this phenomenon. Since coating film does not dissolve in the artificial gastric juice, the dissolution test was performed only in the artificial intestinal juice. The dissolution of indomethacin from the coated sample was changed significantly. Accordingly, coating of the crystals can be performed in order to protect the mucosa of the gastrointestinal tract or to promote the preparation of solid dosage form.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

[Amorphization in pharmaceutical technology].

The amorphization of crystalline active ingredients may be necessary because of the polymorphism of the active substance, the poor water-solubility of the drug material, difficult processing in the crystalline form and the taking out of a patent for a new (amorphous) form. This article introduces protocols for amorphization, which use methods traditionally applied in pharmaceutical technology. The protocols involve three possible routes: solvent methods, hot-melt technologies and milling procedures. With this presentation, the authors suggest help for practising experts to find the correct amorphization method.

Drug Stability↗
PubMed2003

Study of the structure of coherent emulsions.

The object of the study was to analyse relationship between the rheological properties, thermogravimetric behaviour, physical stability, and the wetting contact angle of the lipophilic and aqueous phase of 300 creams of different compositions with a high water content (60-80%, w/w). The starting point was Junginger's theory: water is found in the cream structure in energetic (interlamellar) and steric forms (bulk water). Based on our investigations, an exponential function was found to exist between the contact angle of wetting and the slope of the TG-curves, between the contact angle of wetting and the viscosity of the creams, and between the contact angle of wetting and the evaporation rate of water. A linear relationship was found between the contact angle of wetting and the quantity of water separable by centrifugation.

Drug Stability↗
PubMed2003

[Thermostability testing of iron(II) sulphate for formulation of drug product].

The aim of the experimental study was to determine which iron(II) sulphate form, the monohydrate or the heptahydrate, is more suitable for formulation of a retard dosage form with melt technology, and to control the suitable compound from a thermostability aspect according to the ICH (International Conference on Harmonization). Iron(II) sulphate is susceptible to oxidation and a rise in temperature increases the rate of this redox change. The presence of Fe3+ is definitely harmful in the case of enteral administration. First, the activation energy of the oxidation process was quantified for both iron(II) sulphate forms. It was found that the monohydrate is oxidized four times more slowly than the monohydrate form. It follows from this that the monohydrate well resists short-lived high temperature. The thermostability tests on the monohydrate showed that samples, stored at high temperature and high relative humidity for a long time, oxidized only slowly. On the basis of all these findings, the monohydrate form may be suggested for melt technology.

Drug Stability↗