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Biomedical subjects

G Kedvessy

Publications and source records attributed to G Kedvessy.

At least 37 records · Page 2Linked to original sources
PubMed1982

[On the polymorphism of barbiturates in powders and tablets. 6: Properties and behaviour of a spray-dried barbital preparation].

The manufacture of a spray-dried barbital preparation is described, the properties, tabletting behaviour and release of which were studied in comparison to the initial substance. Spray-drying led to a compression-resistant mixture of amorphous and crystalline particles. As most of these particles have a spherical shape, the tablets obtained from this mixture were of great compactness, which inhibited the penetration of the medium and, consequently, delayed the release of the drug, too.

Barbital↗
PubMed1980

[On the Polymorphism of barbiturates in powders and tablets. Part 4: the dissolution of barbital B and barbital A (modifications I and III and their release from tablets (author's transl)].

Two commercial brands of barbital (A: German Democratic Republic, modification III; B: Hungarian Peopl's Republic, modification I) were used to study the solubility and dissolution of the modifications. Crystals of these two substances were brought into the shape of tablets, the physical parameters and textural properties of which were determined. The effect of polymorphism on the release of these substances is discussed in the light of the results obtained from this investigation. The discussion will be continued and summarized in a subsequent paper, including further modifications.

Barbital↗
PubMed1980

[On the polymorphism of Barbiturates in powers and tablets. Part 5: The dissolution of recrystallized barbital substances and their release from tablet (author's transl)].

The dissolving characteristics of 6 different barbital modifications have been studied. With one exception, the metastable forms dissolved more rapidly than the stable form. The observed differences were not always significant. Substances recrystallized from an acetone-water mixture were less soluble in aqueous solvents than those recrystallized from water. The dissolving characteristics are changed by tabletting, the stable modification being more favourable in this respect. The solubility of barbital A2 was very poor. Consequently, it is not suited for therapeutic use. The dissolution rate was determined by means of the rotating basket method as described in the nineteenth edition of the U.S.P.

Barbital↗
PubMed1979

[On the polymorphism of barbiturates in powders and tablets. Part 1: Crystal optical studies on, and melting behaviour of barbital (author's transl)].

Crystal optical studies showed that barbital brands that conform to the standards of the DAB 7--DDR and the Ph. Hung. VI, respectively, present two different crystalline forms. After recrystallization form water or acetone-water mixture (1:1), the optical crystal picture of the brand conforming to the DAB 7--DDR prevails. The melting points of the commercial products do not differ from each other; both substances melt at 187.5 degrees C, whereas the melting points of the recrystallized products are 1.5 degrees and 2 degrees C, respectively, lower.

Barbital↗
PubMed1979

[On the polymorphism of barbiturates in powders and tablets. Part 2: On the infrared spectroscopy and the X-ray diffractometry of barbital (author's transl)].

By means of IR spectroscopy and X-ray diffractometry, two commercial brands of barbital and four barbital substances recrystallized from water or an acetone-water mixture were examined for polymorphism. The results obtained demonstrate that these substances differ in crystal lattice and that there are six polymorphic modifications.

Barbital↗
PubMed1977

Biopharmaceutical studies on sulphadimidine modifications.

The authors studied sulphadimidine crystal forms with particular reference to the occurrence of polymorphism. They were able to differentiate five crystalline forms by microscopic examination. Differential thermal analysis and IR absorption spectral methods were not reliable. The data from X-ray diffraction patterns of two crystal forms (methanol form I, ethanol form II) were reproducible by estimating their relative intensities. The crystal forms investigated were compared by in vitro and in vivo experiments. Experiments showed that sulphadimidine crystals recrystallized from ethanol had better dissolution and absorption characteristics than sulphadimidine crystals recrystallized from methanol.

Animals↗