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Biomedical subjects

A Sioufi

Publications and source records attributed to A Sioufi.

At least 19 recordsLinked to original sources
PubMed1991

Determination of diclofenac in plasma and urine by capillary gas chromatography-mass spectrometry with possible simultaneous determination of deuterium-labelled diclofenac.

A specific and sensitive method for the determination of diclofenac at concentrations down to ca. 1 ng/ml, the limit of detection being 100 pg/ml, in human plasma and urine by gas chromatography-mass spectrometry with 2H4-labelled diclofenac as internal standard is described. The method is also suitable for the simultaneous assay of these two compounds when both are present in samples of human plasma or urine. In this case, 5-chlorodiclofenac is used as internal standard. After toluene extraction from plasma or without extraction for urine, the method involves the formation of a dimethylindolinone derivative by extractive alkylation. The technique was applied to determine low plasma concentrations and urinary excretion of labelled and unlabelled diclofenac after percutaneous applications of Voltaren Emulgel to humans applied simultaneously under occlusive dressing as deuterated diclofenac sodium, and without occlusive dressing as unlabelled diclofenac sodium.

Deuterium↗
PubMed1991

Determination of diclofenac in plasma using a fully automated analytical system combining liquid-solid extraction with liquid chromatography.

A fully automated analytical system based on liquid-solid extraction combined with column liquid chromatography is described for the determination of diclofenac in plasma. After addition of pH 5 buffer and the internal standard solution to the plasma sample, both sample preparation via a C18 disposable extraction column and injection were performed by a Gilson ASPEC system. Diclofenac and the internal standard were separated on a reversed-phase column, using methanol-pH 7.2 phosphate buffer (56:44, v/v) as mobile phase at a flow-rate of 0.4 ml/min. The reproducibility and accuracy of the method were acceptable over the concentration range 31-3140 nmol/l in plasma.

Chromatography, Liquid↗
PubMed1990

Chromatography of benzodiazepines.

An overview of methods for the determination of benzodiazepines in biological media, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of stability, selectivity, validation, standardization, detection and sensitivity is given. No single technique can be claimed as the method of choice for benzodiazepines. Gas chromatography with electron-capture detection has some strong claims and shows generally good sensitivity and reproducibility. High-performance liquid chromatographic equipment is readily available in most laboratories. The ultimate choice of an assay method for benzodiazepines will be determined by the clinical application (routine monitoring, pharmacokinetics, overdose, forensic medicine) and by the characteristics of the benzodiazepine, the expertise of the analyst, the equipment available, the desired sensitivity and specificity and the time involved in method development or adaptation and validation.

Anti-Anxiety Agents↗
PubMed1990

Influence of exercise on nitroglycerin plasma concentrations after transdermal application.

Nitroglycerin plasma concentrations following transdermal application were measured in nine healthy subjects during supine rest position or during supine rest interrupted by sitting or exercising for 20 min. Sitting led to almost doubling of the average plasma concentrations (0.31 ng ml-1 before sitting, 0.55 ng ml-1 at the end of the sitting period), but exercise was accompanied by a much more marked increase in average plasma concentrations, which reached its maximum 5 min after ending exercise (0.22 ng ml-1 before exercise, 1.26 ng ml-1 5 min after the exercise period). Changes of bioavailability as well as of systemic clearance might be involved in the exercise-induced increase in plasma nitroglycerin concentrations.

Administration, Cutaneous↗
PubMed1989

High-performance liquid chromatographic determination of pirprofen and five of its metabolites in human plasma without hydrolysis and in human urine before and after chemical hydrolysis.

Selective high-performance liquid chromatographic methods for the simultaneous determination of pirprofen and five of its metabolites either in plasma or in urine before and after chemical hydrolysis were developed. After addition of an internal standard and a buffer, the compounds were extracted from plasma using reversed-phase C18 Bond-Elut columns and from urine using pre-packed silica Extrelut 1 columns, back-extraction into sodium hydroxide and acidification of the alkaline phase before injection. Pirprofen, its five metabolites and the internal standard were separated using a linear elution gradient chromatographic system and wavelength programming. The analysis of spiked samples demonstrated the good accuracy and precision of the methods with limits of quantitation of 100 or 200 ng/ml for the different compounds in plasma, 200 or 360 ng/ml in urine without hydrolysis and 1 or 1.8 micrograms/ml in urine after chemical hydrolysis.

Chemical Phenomena↗
PubMed1989

Determination of xylometazoline in plasma and urine by gas chromatography using a fused-silica capillary column and an electron-capture detector.

A sensitive method is described for the determination of unchanged xylometazoline in plasma and urine at concentrations down to 35 nmol/l. After addition of naphazoline as an internal standard, both compounds are extracted with dichloromethane-diethyl ether (20:80) at pH 10, back-extracted with an acidic solution and re-extracted from a sodium hydroxide solution with dichloromethane-diethyl ether (20:80). The compounds are then derivatized with heptafluorobutyric anhydride in the presence of pyridine. The derivatives are determined by capillary gas chromatography using electron-capture detection.

Chemical Phenomena↗
PubMed1989

Pharmacokinetics of a new angiotensin-converting enzyme inhibitor, benazepril hydrochloride, in special populations.

To investigate the pharmacokinetics of benazepril hydrochloride in special populations, single or multiple doses between 5 and 20 mg of the new drug were given, and the pharmacokinetics of unchanged benazepril and its pharmacologically active metabolite benazeprilat were compared with those in healthy male volunteers. In elderly subjects and patients with mild and moderate renal insufficiency, there was little change in the kinetics of benazepril or benazeprilat. In patients with severe renal impairment (creatinine clearance less than 30 ml/min), benazeprilat elimination was slowed, which resulted in greater accumulation after repeated dosing. In patients with hepatic cirrhosis, the kinetics and bioavailability of benazeprilat were not affected. Therefore dose adjustment is unnecessary because of the patient's age, mild or moderate renal impairment, or hepatic cirrhosis. Dose reduction is necessary in patients with creatinine clearance less than 30 ml/min.

Aged↗
PubMed1989

High performance liquid chromatographic determination of nicotine and cotinine in plasma and nicotine and cotinine, simultaneously, in urine.

Three analytical procedures were developed to determine nicotine in plasma, cotinine in plasma and, simultaneously, nicotine and cotinine in urine. After liquid or solid-phase extraction, the purified aqueous phase is injected into a high performance liquid chromatograph equipped with an ultra-violet detector using a CN Spheri-5 micron cartridge-column with an inner diameter of 4.6 mm and a length of 10 or 22 cm. The limit of quantitation for nicotine in plasma was around 8 to 15 ng/ml, that of cotinine in plasma around 50 ng/ml and that of nicotine and cotinine in urine around 170 ng/ml and 70 ng/ml, respectively. The limit of detection of nicotine in plasma was around 1 ng/ml and that of nicotine and cotinine in urine around 20 ng/ml and 10 ng/ml, respectively. The passive exposure to cigarette smoke by non-smokers and the "resting levels" of nicotine in plasma and urine of smokers were studied. The analytical methods were set up to study the pharmacokinetics and bioavailability of nicotine in healthy volunteers following single and repeated administrations of different doses of transdermal nicotine systems.

Amphetamine↗
PubMed1989

Pharmacokinetics and bioavailability of nicotine in healthy volunteers following single and repeated administration of different doses of transdermal nicotine systems.

Healthy nicotine-dependent smokers were applied different doses of transdermal nicotine systems (TNS) during single and repeated administrations. Plasma and urine nicotine and cotinine concentrations were determined by high performance liquid chromatography (HPLC). After single application of TNS, the maximal concentration (Cmax) and area under curve (AUC) of nicotine in plasma as well as the amount of nicotine excreted in urine were linearly related to the dose. The stable urinary cotinine excretion was not influenced by the amount of nicotine delivered by the TNS. The relevant 24 h plasma nicotine concentration reached after TNS application compares well with the plasma nicotine footpoints--not the peaks--observed in moderate to heavy cigarette smokers. A comparison between different nicotine doses from different TNS allowed to conclude to the functionality of the systems as regards pharmacokinetics and bioavailability. One or two hours after removal of the systems, there was a very slow decline of the nicotine concentrations. After repeated application of TNS, there was evidence for only a very limited nicotine accumulation in plasma (+14%) or in urine (+9%) over 10 days. The steady-state of nicotine was reached within 4 days. The continuous delivery of nicotine over 24 h resulted in an early morning plasma concentration which probably decreases or prevents the craving for the first cigarette.

Administration, Cutaneous↗
PubMed1988

Determination of the S(+)- and R(-)-enantiomers of baclofen in plasma and urine by gas chromatography using a chiral fused-silica capillary column and an electron-capture detector.

A sensitive and enantiospecific gas chromatographic method for the determination of the S(+)- and R(-)-enantiomers of baclofen (I and II) in plasma and urine has been developed and validated. The method is based on the complete resolution of the derivatized enantiomers on a chiral fused-silica capillary column. The hydrochloride salt of a (-)-fluoro analogue of baclofen (III.HCl) was used as the internal standard in plasma, the hydrochloride salt of a (+)-fluoro analogue of baclofen (IV.HCl) as the internal standard in urine. Rapid and convenient isolation of the compounds was achieved using reversed-phase Bond-Elut C18 columns. After elution, the compounds were converted into isobutyl esters and purified by base-specific solvent extraction. The isobutyl esters were then N-acylated with heptafluorobutyric anhydride. The derivatives were quantitated after separation on the chiral column using electron-capture detection. The analysis of spiked plasma and urine samples demonstrated the good accuracy and precision of the method, with limits of quantitation of 25 nmol/l for I and II in plasma and of 2 mumol/l for I and II in urine. The method appears to be suitable for use in pharmacokinetic studies of the enantiomers in plasma and urine from animals and man after administration of the racemic baclofen.

Acylation↗
PubMed1988

Simultaneous determination of clomipramine and its N-desmethyl metabolite in human whole blood by capillary gas chromatography with mass-selective detection.

A method for the simultaneous determination of clomipramine and its N-desmethyl metabolite at concentrations down to ca. 2 nmol/l in human whole blood is described. After addition of a known amount of deuterium-labelled internal standards, compounds are extracted into n-heptane-isoamyl alcohol (99:1, v/v) at basic pH, back-extracted into an acidic aqueous solution and re-extracted at basic pH into n-heptane. N-Desmethylclomipramine and the internal standard are derivatized with pentafluoropropionic anhydride. The compounds are determined by capillary gas chromatography with mass-selective detection. The technique was applied to determine the human blood concentrations of clomipramine and its N-desmethyl metabolite after oral administration of Anafranil; mean blood concentrations are reported.

Clomipramine↗
PubMed1987

Determination of the (+)- and (-)-enantiomers of pirprofen in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method was developed to determine the (+)- and (-)-enantiomers of pirprofen, an anti-inflammatory drug. After addition of an internal standard, the plasma sample was brought onto a glass column pre-packed with silica and eluted with dichloromethane. The extracts were derivatized with 1,1'-carbonyldiimidazole and R (+)-1-methylbenzylamine to form the two diastereomeric amides. The diastereoisomers were separated on a chiral column by HPLC with ultraviolet detection at 272 nm using n-hexane-dichloromethane (64:36, v/v) as the mobile phase. The limit of quantitation was 0.992 mumol/l (0.25 microgram/ml) for each enantiomer.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

Determination of the two dinitrate metabolites of nitroglycerin in human plasma by capillary gas chromatography with electron-capture detection.

This paper describes a sensitive method for the specific determination of 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate as metabolites of nitroglycerin at concentrations down to 250 pg/ml plasma. After addition of a known amount of 2-isosorbide mononitrate as internal standard, plasma is introduced onto an Extrelut cartridge and the compounds of interest are eluted with dichloromethane. The glyceryl dinitrates are then quantitated by capillary gas chromatography with electron-capture detection.

Chromatography, Gas↗
PubMed1986

[The percutaneous absorption of diclofenac].

The percutaneous absorption of diclofenac diethylammonium 1.16% (w/w) in a combination of emulsion cream and gel (Voltaren Emulgel) and of diclofenac sodium 1% (w/w) in a cream formulation (Voltaren cream) was investigated in guinea-pig, rabbit and man. The percutaneous absorption of diclofenac sodium in guinea-pig was 3 to 6% of the dose when the cream formulation in doses of 320, 100 or 40 mg was applied on 10 cm2 of occluded skin and left in place for 6 h. The transdermal delivery of 14C-labelled diclofenac yielded plateau plasma concentrations of radiotracer from 1.5 h after application until removal of the residual cream. Subsequently the steady state drug depots in the skin and muscle tissue were depleted promptly. During daily administration the steady state levels in the muscle tissue in proximity to the application site were about 3 times higher than in distant muscle tissue. By topical application on knee joints of rabbits diclofenac penetrated into the patellar ligament, the adipose corpus and the synovial fluid. In man the percutaneous absorption was 6% of the dose when the Emulgel formulation was spread by 5 mg/cm2 and left for 12 h on non-occluded skin. The pattern of metabolites of diclofenac in human urine was the same after topical and oral administration. In man, upon daily topical administration of 3 times 2.5 g cream formulation (10 mg/cm2) the diclofenac steady state plasma levels were 20 to 40 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Quantitative determination of nitroglycerin in human plasma by capillary gas chromatography with electron-capture detection.

A sensitive method for the selective determination of nitroglycerin at concentrations down to 50 pg/ml in human plasma is described. After the addition to plasma of a known amount of butane-1,2,4-triol trinitrate as internal standard, both compounds are extracted into hexane. Nitroglycerin is then quantitated by capillary gas chromatography with electron-capture detection.

Chromatography, Gas↗
PubMed1985

Simultaneous determination of pirprofen and its metabolite, the pyrrole derivative, in plasma by high-performance liquid chromatography.

A method for the simultaneous determination of pirprofen and its metabolite, the pyrrole derivative, in human plasma is described. The two compounds and the butyric acid analogue of the pyrrole derivative used as internal standard are extracted from plasma with chloroform, then back-extracted into an alkaline buffer. After addition of acid, the aqueous phase is assayed by high-performance liquid chromatography using a fixed-wavelength ultraviolet detector at 254 nm. The limit of quantitation is 0.1 micrograms/ml (0.396 mumol/l for pirprofen and 0.400 mumol/l for the pyrrole derivative).

Anti-Inflammatory Agents, Non-Steroidal↗