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Biomedical subjects

Z Zatloukal

Publications and source records attributed to Z Zatloukal.

At least 19 recordsLinked to original sources
PubMed2005

[Power law equation and liberation kinetics].

For the modelling of the kinetics of diffusion and relaxation in the polymer matrix, the power law equation in a two-parameter or three-parameter form is employed. The introductory part of the paper summarizes the employed varieties of the power law equation including the equation making it possible to distinguish diffusion from relaxation. The liberation kinetics of pilocarpinium chloride from lyophilized lamellae with graded amounts of hydroxypropylmethylcellulose is expressed by power law equations and their parameters are compared. The conclusion discusses the usability of the power law equation in the modelling of liberation of active ingredients and recommends the use of the three-parameter power law equation with a shift of the liberation out of the origin of the coordinates.

Chemistry, Pharmaceutical↗
PubMed2005

[Penetrometry used for the estimation of flow rate].

Penetrometry through a cone is a standardized method of comparing the consistence of semisolid systems. For the time being, this arrangement is only of marginal importance for the evaluation of flow ability of powders. For this purpose it is recommended to use penetrometry by means of a ball, which is significantly connected with the volume flow rate. The present original paper attempts to find the regression dependence suitable for the estimation of the flow rate of size fractions by means of powdered auxiliary substances. This solution replaces the traditional penetrometric degrees (unit of length) with volume or weight of freely layered powder pushed out by the penetrating ball. The optimal method is the transformation of penetrometric degrees to the weight of the powder, which makes it possible to estimate the weight rate of pouring with the use of an exponential equation elucidating 97.4% of total dispersion. Penetrometry with the use of a ball could be included into the group of tests for the evaluation of flow ability and structure of powdered auxiliary substances.

Particle Size↗
PubMed2005

Systematic study of factors affecting eye drop size and dosing variability.

The application of eye drops is known to be problematic due to the high variability of eye drop volume, the low capacity of the precorneal area resulting in an optimal drop volume of about 20 microl, and the risk of adverse systemic effects of drugs due to systemic absorption via the nasal mucosa. While dropper tip design and the surface activity of the antimicrobial preservative strongly influence the volume of an aqueous ophthalmic solution dispensed as eye drops, the handling of the preparation (dispensing angle, dispensing rate, and the residual volume of liquid in the dropper bottle) is generally believed to produce a minimal effect. In this study, properties of two dropper tips (rubber and plastic) frequently used in the Czech Republic were systematically investigated in a fractional factorial experiment. Of seven determinants potentially influencing the size of eye drops, the dropper tip design, the dispensing angle and the dispensing rate have been found to have a significant effect on the eye drop volume. Wetting of the rubber dropper tip resulted in a dramatic increase in drop volume which could hardly be foreseen in real drop dispensing. As a result, therefore, rubber dropper tips could scarcely be recommended, as opposed to plastic dropper tips which produced drops of comparable volume when used in upright position with approximately the same dispensing rate. Under those defined dispensing conditions, the variability of the drop volume could be expressed by a variability coefficient of 3.3%. Using a dispensing angle of 45 degrees from horizontal led to a decrease in drop volume and, in addition, to greater volume variability due to the formation of air bubbles inside the dropper tip chamber.

Algorithms↗
PubMed2004

[Statistical aspects of drug dosages in random powder mixtures].

The precision of dosing of powder drugs in piece dosage forms can be theoretically forecast by means of statistical principles of variability of random mixtures, the use of which for this purpose has been traditionally examined. The present critical review of the literature of the subject is primarily focused on random mixing of powder mixtures, their homogeneity, volume dosing, and the use of a correlogram in the examination of nonrandom and segregated mixtures. The knowledge is useful both for the selection of a suitable particle size and for the verification of suitability of the employed parameters of mixing and the technological processing of the obtained mixture.

Models, Statistical↗
PubMed2004

[Interactive powder mixtures].

Linking up with the statistical aspects of dosing the active ingredient in the random powder mixture, the properties of non-random mixtures of micronized active ingredients with auxiliary substances of the particle size larger by an order are summed up. The review of literature aims to report the conditions of the development of interactive mixtures, possible more precise dosing of small amounts of active ingredients, and limitation of the risk of ordered unit segregation. From the technological standpoint, interactive mixtures are relevant primarily for direct compression of tablets and dosing of the micronized active ingredient in dry powder inhalers. From the theoretical standpoint, the data concerning a temporary increase in the solubility of some active ingredients after the development of an amorphous surface during long-term mixing of interactive powder mixtures are of interest.

Chemistry, Pharmaceutical↗
PubMed2004

[Weibull equation and dissolution kinetics].

On modelling the kinetics of dissolution, two variants of Weibull equation in a two-parameter or tree-parameter form are used, the estimations of their parameters not being quite comparable. The introductory part of the paper sums up four variants of the equation and chracterized their relationship to granulometric Rosin-Rammler-Sperling equation. The kinetics of liberation of pilocarpinium chloride from lyophilized lamellae with graded amounts of hydroxypropylmethylcellulose is expressed by the above-mentioned equations and their parameters are compared. The conclusions generally discusses the usability of equations and their correct interperetation in modelling dissolution of active ingrediens from dosage forms.

Chemical Phenomena↗
PubMed2003

[Kinetics of scopolamine bromide release from hydrogel with a filtering membrane].

The hydrated filtration membrane renders possible uniform hydration of hydroxypropylmethylcellulose hydrogel with subsequent uniform release of dissolved scopolamine bromide. Exponential dependence of the diffusion coefficient on the graded medium dimension of the pores of the testing membrane makes possible the estimation of the reactive fractal dimension DR by means of the modified exponent (3-DR). With increasing concentration of scopolamine bromide in xerogel (14.7 to 77.8 mg/cm3), DR decreases within a range of 2.814 to 2.704. A comparison with the structure of a suitable fractal (Menger sponge) leads to a conclusion about suitability of the use of membranes for the testing of concentrations of scopolamine bromide in xerogel, if DR > 2.727.

Chemical Phenomena↗
PubMed2003

[Penetrometry in evaluation of flow and structure of powdered substances].

Usability of modified penetrometry is examined and significant relationships with routinely used characteristics of flowability and structure of powdered substances are searched for in size fractions of sodium chloride, potassium chloride, sodium citrate, and potassium citrate. A systematic study of interrelationships between properties made it possible to achieve sufficiently reproducible results without a necessity of consolidation. By means of factor analysis, a connection between penetrometry, bulk flow rate, and Kawakita-constant was demonstrated. For multidimensional linear regression for estimation of penetrometry, the significance of examined properties decreases in the order Kawakita-constant > loose bulk density > total porosity > bulk flow rate > mass flow rate. The most important item of knowledge gained in the study is the dependence of penetrometry on a combination of loose bulk density and Kawakita-constant.

Citrates↗
PubMed2003

[Effect of pilocarpine chloride on pseudoplastic hydrogel].

Colloidal aqueous dispersions of 2 to 5% (weight) of hydroxypropylmethylcellulose (HMPC 4000) yield pseudoplastic mucilages and gels. Rotational viscosimetry in the cone-plate arrangement enables rapid and reproducible evaluation of the transitional region between pseudoplastic and plastic deformation, characterized by Herschel-Bulkley equation. To the traditional Ostwald's two-parameter relationship it adds a third one, revealing a deviation from the beginning of the coordinates of the rheogram caused by the limiting yield stress. The obtained equations make it possible not only to estimate apparent and real viscosity, but also the area under the curve of the pseudoplastic rheogram. The actual precondition of integration, however, is the estimation of the limiting yield stress as the shear rate for the zero shear stress. Experimental estimation of the bottom margin for the integration of the area under the curve makes mutual comparability of rheograms possible. At a temperature of 32 degrees C, analysis of variance demonstrated a significant diminution of this area in the presence of about 2% of pilocarpinium chloride.

Chemical Phenomena↗
PubMed2003

[Granulometry and fractal dimensions].

The fractal character of exponential particle size distribution makes it possible to use fractal dimension for the evaluation of the results of granulometric analysis. The conditions of sedimentation analysis of talc in aqueous solution were optimized by adding nonionogenic tenside and deflocculation electrolyte. Dispersion analysis demonstrated the suitability of minimally 0.2 g/l of polysorbate 80 for talc soaking. In the evaluation of pharmaceutical granulometry, it is advisable to supplement the usually reported specific surface area with fractal dimension, which primarily contributes to a more general interpretation of variability of particle size.

Chemistry, Pharmaceutical↗
PubMed2002

[Effect of fractal dimensions of powdered pharmaceutical aids on their flow rate].

Fractal dimension of the particles of powdered auxiliary substances expresses the raggedness of their surface, which can influence both the bulk density and their flow rate through the opening of the powder funnel. In the size fractions of 0.20-0.25 mm of six powdered auxiliary substances, their linear fractal dimensions within a range of 1.031 to 1.109 and the corresponding flow rates through the circular openings of the powder funnel of diameters of 6; 8; 10, and 12 mm were found. A significant correlation has been demonstrated between the flow rate expressed in volume (cm3/s) and the fractal dimension, which after an increase by one unit characterizes the surface of the particles. With increasing fractal dimension, the porosity of freely poured layer of powdered auxiliary substances is increased and simultaneously also their flow rate expressed in volume. For the usually reported flow rate expressed in weight (g/s), such influence is not significant.

Chemical Phenomena↗
PubMed2002

[Reactive fractal dimension in the release of scopolamine bromide from hydrogel].

First-order release kinetics is characterized by a linear dependence of the release rate on the released amount of the active ingredient, the triple of the absolute value of the exponent of the exponential function expressing the reactive fractal dimension DR. Scopolamine bromide release from hydroxypropylmethylcellulose hydrogel was first expressed by first-order kinetics with an estimated DR ranging from 2.98-3.00. The employment of an exponential equation with the exponent of release n renders it possible to make an assumption about the mechanism of release. Within a range of n = 0.505-0.550, estimated DR = 2.46-2.94. In this region, release by means of the mechanism of Fick's diffusion prevails. DR = (3/n)-3 generally holds true for the relationship between both variables, which makes it possible to use the knowledge gained in the experimental influencing of the exponent of release in the examination of the relationship between the reactive fractal dimension and the mechanism of release of scopolamine bromide from hydrogel. An increase in the exponent of release markedly decreases the corresponding values of reactive fractal dimension.

Chemistry, Pharmaceutical↗
PubMed2000

[Fractal dimensions of powders used as pharmaceutical dusting powders].

The paper examines the use of the fractal dimension for the expression of the shape of random aggregates of primary particles of four powders for pharmaceutical dusting powders. The values within a range from 1.14 to 1.24 are compared with the results of the equilibrium gravitational classification within a range from 15 to 45 microns. Vacillation of the fractal dimension is influenced by the values of the specific surface determined from the parameters of the RRS-distribution of elutriation. The fractal dimension extends the morphological characteristics of powders. For the needs of pharmaceutical technology it is, however, necessary to specify better the conditions of its determination, above all in the selection of a suitable range of the dimension of evaluation ("walk") with regard to the largest dimension of the aggregates of powders.

Particle Size↗
PubMed2000

[Effect of electrolytes on hydration of lyophilized xerogel] .

Using a hydrated filtering membrane, the rate of hydration of the lyophilized xerogel hydroxypropylmethyl cellulose (HPMC) 4000 with an isotonic solution of sodium chloride was examined. The presence of the electrolyte influences the kinetics of diffuse hydration linearized by the root of time. Sodium chloride or pilocarpinium chloride significantly accelerates hydration compared with the hydration of xerogel alone. The effect of atropinium sulphate and scopolaminium bromide is not significant. Significant correlation was demonstrated between the density of HPMC 4000 in xerogel and the rate of its hydration. This density can be influenced by the conditions of lyophilization or the kind and amount of the added active ingredient.

Electrolytes↗
PubMed1989

[Pharmacotherapy in a stomatological ward followed by a computer].

Based on regular information from a computer an annual evaluation of prescribed drugs in a stomatological ward was done. The most frequently prescribed drugs were antibiotics in 38.85%, stomatological drugs in 19.52% and vitamins in 12.39%. Further extended use of computer in a stomatological practice and a possibility of mutual connection of several stomatological workplaces, in the systems of data, their collection and transfer to the central computer of the ward, would significantly contribute to a more precise evaluation of pharmacotherapy even in connection with other indices of stomatological records.

Anti-Bacterial Agents↗
PubMed1989

[Interactions of drugs with PHEMA hydrogel].

Hydration of polyhydroxyethylmethacrylate (PHEMAs hydrogel with aqueous solutions of medicinal substance) renders it possible to deposit medicinal substances within the hydrogel. At the same time the concentration of the medicinal substances in the hydrogel is higher than their concentration in the hydrating solution. For the nonspecific interactions, which affect the deposition of medicinal substances in hydrogel, their surface tension is of principal importance. With decreasing surface tension the amount of medicinal substances in hydrogel is increased and simultaneously their release into the aqueous medium is decelerated. Interactions of six selected medicinal substances with PHEMA hydrogel were experimentally checked in the in vitro conditions.

Drug Interactions↗