Search results for "reparation"
showing 10 items of 944 documents
Determination of trace amounts of β tegafur in commercial α tegafur by powder X-ray diffractometric analysis.
2011
Abstract Objectives The main objective of this work was to develop a suitable analytical technique for determining trace amounts of the thermodynamically stable solid form in bulk samples of metastable form, to a sensitivity of 0.005%–1.0%. Tegafur (5-fluoro-1-(tetrahydro-2-furyl)-uracil) α and β crystalline forms were used as a model for this problem. Methods The trace content of the thermodynamically stable β polymorphic form in tegafur samples was increased by promoting phase transition from the bulk of thermodynamically metastable α form to β form, and achieving sufficient β form content for a quantitative powder X-ray diffractometry (PXRD) analysis. The phase transition was stimulated …
Investigation of various shellac grades: additional analysis for identity.
2009
Background: A number of different grades of shellac are commercially available and most of them are known only as generic shellac and are not further differentiated. The investigated grades of shellac in this study are based on different insect strains, host trees, refining methods, and products from different suppliers. Method: The Gardner/Iodine color values of alcoholic and aqueous solutions of the various shellac grades were measured. Glass transition temperatures and pKa-values were determined. To assess chemical differences in the tested shellac grades, MALDI-TOF analysis was performed. Results: Differences were found in color, TG, and pKa-values and in the mass spectra by MALDI-TOF a…
A topological sub-structural approach for predicting human intestinal absorption of drugs.
2004
The human intestinal absorption (HIA) of drugs was studied using a topological sub-structural approach (TOPS-MODE). The drugs were divided into three classes according to reported cutoff values for HIA. "Poor" absorption was defined as HIAor =30%, "high" absorption as HIAor =80%, whereas "moderate" absorption was defined between these two values (30%HIA79%). Two linear discriminant analyses were carried out on a training set of 82 compounds. The percentages of correct classification, for both models, were 89.02%. The predictive power of the models were validated by three test: a leave-one-out cross validation procedure (88.9% and 87.9%), an external prediction set of 127 drugs (92.9% and 80…
Multivariate equivalence tests for use in pharmaceutical development.
2014
Statistical equivalence analyses are well-established parts of many studies in the biomedical sciences. Also in pharmaceutical development and manufacturing equivalence testing methods are required in order to statistically establish similarities between machines, process components, or complete processes. This article presents a choice of multivariate equivalence testing procedures for normally distributed data as generalizations of existing univariate methods. In all derived methods, variability is interpreted as nuisance parameter. The use of the proposed methods in pharmaceutical development is demonstrated with a comparative analysis of dissolution profiles.
Introduction to molecular topology: basic concepts and application to drug design.
2012
In this review it is dealt the use of molecular topology (MT) in the selection and design of new drugs. After an introduction of the actual methods used for drug design, the basic concepts of MT are defined, including examples of calculation of topological indices, which are numerical descriptors of molecular structures. The goal is making this calculation familiar to the potential students and allowing a straightforward comprehension of the topic. Finally, the achievements obtained in this field are detailed, so that the reader can figure out the great interest of this approach.
Strategies and Molecular Probes to Investigate the Role of Cytochrome P450 in Drug Metabolism
2003
Drug metabolism is the major determinant of drug clearance and, because of polymorphic or inducible expression of drug-metabolising cytochrome P450s (CYPs), is the factor most frequently responsible for interindividual differences in pharmacokinetics. A number of well characterised CYP substrates and inhibitors have been identified that allow precise measurements of individual CYP isoforms. Their use, alone or in combination, facilitates the phenotype characterisation of hepatocytes in vitro and in vivo. Two procedures are used for in vitro investigation of the metabolic profile of a drug: incubation with microsomes and incubation with metabolically competent cells. The major limitation of …
Bioequivalence of oral products and the biopharmaceutics classification system: science, regulation, and public policy.
2011
The demonstration of bioequivalence (BE) is an essential requirement for ensuring that patients receive a product that performs as indicated by the label. The BE standard for a particular product is set by its innovator, and this standard must subsequently be matched by generic drug products. The Biopharmaceutics Classification System (BCS) sets a scientific basis for an improved BE standard for immediate-release solid oral dosage forms. In this paper, we discuss BE and the BCS, as well as the issues that are currently relevant to BE as a pharmaceutical product standard.
The Prediction of Human Intestinal Absorption Based on the Molecular Structure
2014
Human Intestinal Absorption (HIA) has been modeled many times by using classification models. However, regression models are scarce. Here, Artificial Neural Networks (ANNs) are implemented for this purpose. A dataset of structurally diverse chemicals with their respective experimental HIA were used to design robust, true predictive and widespread applicable ANN models. An input variables pool was made up of structural invariants calculated by using either Dragon or our software Desmol 1. The selection of best variables was performed following three steps using the entire dataset of molecules. Firstly, variables poorly correlated with the experimental data were eliminated. Secondly, input va…
Nebennieren undrenale Oxytocin-Wirkungen bei der Ratte
1959
No significant improvement in water diuresis was obtained by the s. c. injection of 500–1000 mU/kg of a synthetic oxytocin preparation (Syntocinon) in adrenalectomized, salt-maintained rats given 18 ml of water per rat by stomach tube. In these animals oxytocin had, on the other hand, a strong natriuretic and chloruretic effect.