Search PubMed⌕ Search

Biomedical subjects

J Szejtli

Publications and source records attributed to J Szejtli.

At least 37 records · Page 2Linked to original sources
PubMed1985

Cyclodextrins: a new group of industrial basic materials.

Adequate toxicological studies, discovery of numerous potential fields of utilization and last but not least, the production of cyclodextrins on industrial scale with high homogeneity and low price led to their recognition as a new group of industrial basic materials. Until now cyclodextrins were considered merely as agents for molecular encapsulation, however intensive research of the past few years revealed quite new and unexpected aspects: cyclodextrins, their derivatives and polymers can be applied--not exclusively due to their complexing ability--in foods, cosmetics, pharmaceuticals, chromatography, pesticide formulations, in photochemistry, etc.

Catalysis↗
PubMed1985

Quantitative structure-stability relationships among inclusion complexes of cyclodextrins. I: Barbituric acid derivatives.

Quantitative structure-stability relationships (QSSRs) are formulated for the inclusion complexation of 17 barbituric acid derivatives with alpha- and beta-cyclodextrin. The variation in the complex stability constants K alpha and K beta is found to be partly accounted for by the molar refractivity or the hydrophobicity of the substituent R1 at position 5 of the barbiturate ring. In addition, K alpha also depends upon whether or not R1 is branching or cyclic, and K beta also depends upon whether the guest molecule is a barbiturate or a thiobarbiturate. The results suggest that in alpha-cyclodextrin-barbiturate complexes the cyclodextrin cavity includes only R1, while in beta-cyclodextrin complexes both R1 and (part of) the barbiturate ring are included. This complexation model is compared with those proposed by other authors.

Barbiturates↗
PubMed1985

Suppositories containing cyclodextrin complexes. Part 2: Dissolution and absorption studies.

The dissolution and absorption of poorly water-soluble drugs from rectal suppositories can be enhanced by complexing these substances (e.g., essential oils, indomethacin) with beta-cyclodextrin. Preliminary in vivo studies showed, that the application of cyclodextrin complexes to suppositories, the same as to oral applications, resulted in an increased blood level.

Absorption↗
PubMed1985

Absorption, distribution, excretion and metabolism of orally administered 14C-beta-cyclodextrin in rat.

The absorption, distribution, excretion and metabolism of orally administered universally labelled 14C-beta-cyclodextrin and 14C-glucose were compared in rat. The maximum radioactivity of the blood derived from 14C-beta-cyclodextrin was observed between 4th and 11th h and the value of the maximum in different experiments ranged between 5 and 17 0/00 of the total administered radioactivity. Following 14C-glucose treatment radioactivity reached the maximum within half-an-hour, with values of 15 to 82 0/00. In the 8th h after a high dose (313.5 mg/kg) of beta-cyclodextrin no more than 3-50 ppm beta-cyclodextrin was detectable in the blood by HPLC. After 14C-beta-cyclodextrin treatment 4.2-4.8% of the administered total radioactivity was excreted by the urine and about the same quantity (2-3.6%) in case of 14C-glucose. No specific accumulation was observed after 14C-beta-cyclodextrin treatment in the different organs. The large intestine contained 10-15% of the cyclodextrin radioactivity while this value was only 2% in case of 14C-glucose. Following p.o. administration of different doses of 14C-beta-cyclodextrin the radioactivity peak was detected in the exhaled air between the 4-6th and 6-8th h, respectively, depending on the administered doses, while in case of 14C-glucose treatment it was observed within 2 h. The total radioactivity exhaled by 14C-beta-cyclodextrin treated animals in 24 h was 55 to 64% of the administered radioactivity and 58% in case of 14C-glucose. It is assumed that beta-cyclodextrin is metabolized in rats slower but similarly to glucose, therefore p.o. administered beta-cyclodextrin cannot induce toxic symptoms.

Administration, Oral↗
PubMed1984

Cyclodextrin polymer, a new tablet disintegrating agent.

Cyclodextrin (CD) polymer, a type of crosslinked cyclodextrin, has been evaluated as a new tablet disintegrating agent in comparison with four common disintegrants (crosslinked polyvinylpyrrolidone, crosslinked carboxymethyl cellulose, formaldehyde casein and corn starch). Physical properties of the disintegrants have been studied. Tablets made by direct compression using microcrystalline cellulose as binder, magnesium stearate as lubricant and talc as antiadherent have been compared. The parameters evaluated were disintegration time, hardness and friability. CD polymer performs well as a tablet disintegrating agent with results paralleling those of crosslinked carboxymethyl cellulose (Ac-Di-Sol) and superior to the other three.

Cellulose↗
PubMed1984

Cyclodextrin-stabilized volatile substances for inhalation therapy.

Diapulmon (Chinoin) which comprise camphor, 1-menthol, eucalyptus oil and quinine dissolved in sunflower oil (Oleum helianthi) is marketed in ampoules of 2 ml but utilized almost exclusively for inhalation therapy. Complexing the active ingredients of Diapulmon with beta-cyclodextrin (beta-CD) a stable non hygroscopic microcrystalline substance is obtained. When this powder sprinkled on hot water, the included volatile compounds are gradually released and the desired pharmacological effect can be brought about.

Camphor↗
PubMed1984

Simulation of pharmacokinetic behaviour of drug-cyclodextrin complexes.

Complexation with cyclodextrin decreases the hydrophobicity of poorly soluble drugs and results in enhanced dissolution rates and higher solubility. In vivo experiments showed that this "molecular encapsulation" of drugs leads to enhanced bioavailability, which is controlled by the solubilities, stability constants of the complexes, the molar ratio of drug: cyclodextrin, etc. This modification of the pharmacokinetic processes has been simulated by computing the theoretical blood level curves. These computer-simulated curves seem to be appropriate models of the experimental observations. Knowing the numerical values of the parameters utilized in these computer simulations, the modification of the pharmacokinetics can be predicted when using cyclodextrin complexes in oral dosage forms.

Adsorption↗
PubMed1983

Improvement of the absorption of 3H-Cholecalciferol by formation of its cyclodextrin complex.

Following oral administration to rats of beta-cyclodextrin inclusion complex of 3H-labelled vitamin D3 (cholecalciferol) resulted in significantly higher blood radioactivity as with the non-complexed vitamin. Difference in the first 90 min was 2,3-2,8 fold, and it remained significantly higher up to the 6th h. After 24 h there was no difference between the blood radioactivity of animals treated with complexed and with non-complexed vitamin D3.

Cholecalciferol↗
PubMed1983

Preparation, properties and biological activity of beta-cyclodextrin inclusion complex of menadione.

The molar ratio of menadione (vitamin K3) to beta-cyclodextrin in the microcrystalline inclusion complex showed this to be 1:3 with a menadione content of approximately 4.1-4.3%. Complexes with higher vitamin content could not be prepared. Bound and free vitamin can be readily separated by sublimation in vacuum. The menadione is highly stable in complexed form; in dry state it is released only when cyclodextrin is destroyed by heating to about 300 degrees C. Complexed menadione does not react with amino acids. Solubility and dissolution rate are strongly increased. Treating hypovitaminotic chickens with equivalent doses of menadione or menadione-beta-cyclodextrin complex and monitoring blood clotting times, recalcification times and prothrombin times the complex proved to be at least as effective as--or even somewhat more potent than--free vitamin. 1.5-2.0 micrograms/animal/d free or complexed menadione was sufficient to cover the daily vitamin K needs of chickens.

Animals↗
PubMed1981

Influencing of resorption and side-effects of salicylic acid by complexing with beta-cyclodextrin.

After oral administration of 14C-labelled salicylic acid and its beta-cyclodextrin complex to rats, the blood radioactivity-level increases in the first 2 h than decreases. The blood level obtained with the inclusion complex is somewhat but not significantly lower than with free acid. Since the resorption of cyclodextrin is a considerably slower process, it is very likely that the resorption of salicylic acid take place in the form of free acid after dissociation of the complex. The urinary excretion cumulative curves show that the free salicylic acid is completely excreted, while about 10% of the salicylic acid administered in the form of complex is lost. The cyclodextrin complex formation increases the pK value of all hydroxy-benzoic acids. Direct observations reveals that complex formation decreases the stomach-irritating effect of salicylic acid. The ratio of radioactivity was nearly the same in the organs of animals treated by both free salicylic and cyclodextrin complex.

Animals↗
PubMed1981

Interaction between indometacin and beta-cyclodextrin.

CHINOIN-137 consists of indometacin and beta-cyclodextrin in a 1 : 2 molar ratio. solid phase analytical techniques, as thermal analysis, mass spectrometry and X-ray powder diffraction do not support the existence of a well-defined crystalline complex. However this product dissolved in water more readily and results in a higher indometacin concentration than indometacin itself. The formation of an inclusion complex with a reasonable stability in aqueous solution was proved by diffusion tests and chiroptical properties. Following oral administration of CHINOIN-137 to rats, higher blood levels (by about 25%) of indometacin can be achieved than with the uncomplexed drug. A significant difference was observed in the absorption of 14C-labelled indometacin and its cyclodextrin complex by "in loco" techniques in the small intestines of anaesthetized rats: from indometacin 56%, from the complex 68% of the activity was resorbed within 10 min.

Animals↗