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Biomedical subjects

O Lafont

Publications and source records attributed to O Lafont.

At least 55 records · Page 3Linked to original sources
PubMed1989

[Synthesis of potential metabolites of a barbiturate containing two branched side chains].

The two branched side chains of 5-(3-methylbutyl)-5-(2-methylpropyl)-barbituric acid present a tertiary carbon atom, which can be oxidized in vivo by hepatic enzymes. Potential metabolites of this compound are synthesised: the gamma-hydroxy metabolite can be oxidized directly by CrO3 while the beta-hydroxy metabolite can only be prepared by hydration of a double bond. This beta-hydroxybarbiturate then undergoes an alcoholysis leading to an allophanyl-gamma-lactone, which is hydrolysed into a carboxylic lactone, which can give a lactone by decarboxylation. On the other hand, a beta-gamma-dihydroxymetabolite is synthesised by double hydration of two double bonds using two different methods. A spirobilactone can also be synthesised from this dihydroxy compound.

Barbiturates↗
PubMed1988

[Not Available].

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Economics, Medical↗
PubMed1988

[Not Available].

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France↗
PubMed1988

Interaction between allopurinol and pyrazinamide.

Pyrazinamide (PZA) is increasingly used with isoniazid and rifampicin, in short-course antituberculous chemotherapy in service programme conditions. Complicating arthralgias occur due to hyperuricaemia induced by the inhibition of renal tubular secretion of uric acid by pyrazinoic acid, the main PZA metabolite. Allopurinol (Al), a hypouricaemic agent, provides no substantial clinical improvement. Pharmacokinetics of PZA and its metabolites were studied in six healthy volunteers, in a cross-over design, after a single oral dose of PZA alone and, in a second trial, after the same dose together with Al. Plasma and urinary concentrations were measured by high pressure liquid chromatography with a column of cation exchange resin. Analysis of the pharmacokinetic parameters showed that Al induced marked changes in levels of PZA metabolites and accumulation of pyrazinoic acid. Despite decreasing uric acid synthesis, allopurinol increased plasma concentrations of pyrazinoic acid, which is directly responsible for the inhibition of renal urate secretion. Other drugs, which do not involve xanthine oxidase inhibition, should be used in the treatment of this side effect of chemotherapy.

Adult↗
PubMed1987

[Microdetermination of pyrazinamide and its metabolites (pyrazinoic acid, 5-hydroxypyrazinoic acid, 5-hydroxypyrazinamide and pyrazinuric acid) in plasma and urine with liquid chromatography].

The method reported here for determining pyrazinamide and its metabolites (2-pyrazinoic acid, 5-hydroxypyrazinamide, 5-hydroxypyrazinoic acid and pyrazinuric acid) consists of diluting urine or acid deproteinisation of serum followed by chromatography on a cation-exchange column. The column length and the detection system (ultraviolet or fluorimetry) allow for a very good separation of the different compounds; the sensitivity of the method makes it suitable for pharmacokinetic studies.

Chromatography, High Pressure Liquid↗
PubMed1987

[Determination of plasma ethambutol with liquid chromatography and ultraviolet spectrophotometry].

The method presented here is based on the ability of ethambutol to give chelates with divalent cationic metals. With copper salts, the chelate presents a characteristic ultraviolet absorbance at 270 nm, making it possible to titrate ethambutol extracted from plasma with chloroform in alkaline medium. The column which was used contained silica (LiChrosorb Si 60, 5 microns) and the mobile phase was a mixture of equal parts of water and acetonitrile, containing copper sulphate and ammonia. The internal standard was a lower homologue of ethambutol with the same chelating ability. The detection limit was 0.15 mg/l. No interference with other antitubercular agents was observed.

Ammonia↗
PubMed1987

[Simultaneous microdetermination of pyrazinamide and pyrazinoic acid by liquid chromatography].

The technique reported here enables to titrate concomitantly pyrazinamide as well as its main metabolite, the 2-pyrazinoic acid. The serum sample is deproteinized with acetonitrile and the portion floating on the surface is injected on an anionic column of copolymer. The detection occurs at 270 nm and the sensitivity of the method enables its use during pharmacokinetic studies. The other anti-tuberculous drugs, usually associated, produce no interference.

Acetonitriles↗
PubMed1985

[Not Available].

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France↗
PubMedDate not supplied

Passage of allophanoyl-gamma-lactones through the kidney.

In order to establish if allophanoyl-gamma lactones (B compounds) can pass through the kidney or if only the corresponding delta-hydroxybarbiturates (A compounds), formed by intramolecular alcoholysis, are able to do so, nine experiments were performed to study the urinary excretion of four different allophanoyl gamma-lactones B after administration to dogs. Excreted compounds were extracted, identified and quantised. From the amounts of unmodified administered lactones that were recovered, it is concluded that B compounds can pass through the kidney before isomerisation into the corresponding barbiturates A.

Animals↗
PubMedDate not supplied

[Chromic oxidation and synthesis of barbiturate metabolites].

Chromic oxidation using chromium trioxide in acetic medium is presented as a tool for the synthesis of models of metabolites of various barbiturates. When the pyrimidinetrione is monosubstituted in position 5, a hydroxy group is introduced on the ring. For 5,5-disubstituted barbiturates, branched chains are preferentially converted into tertiary alcohols, while ethylenic chains are, according to their substitution, oxidized into ketones or carboxylic acids. Secondary alcohols lead to ketones but an alcohol function can be protected by esterification. Oxidations followed by other transformations and oxidations of related heterocycles are also described.

Barbiturates↗