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Biomedical subjects

A Sioufi

Publications and source records attributed to A Sioufi.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1984

Determination of pirprofen in biological material by gas-liquid chromatography with nitrogen-specific and electron-capture detection.

Pirprofen, 2-[3-chloro-4-(3- pyrrolin -1-yl)phenyl]propionic acid, is an analgesic and anti-inflammatory agent. Most of the pirprofen is present in plasma in the unchanged form (80-90%), the remainder in the form of the pyrrole derivative. However, pyrrole is also formed during sample manipulation by oxidation of pirprofen. Thus, a method based on conversion of pirprofen to pyrrole by oxidation with 2,3- dicyano -5,6- dichlorobenzoquinone and subsequent measurement of the total pyrrole concentration was developed. The method is based on the introduction of an internal standard, extraction and esterification followed by oxidation. The methyl ester of the pyrrole is then determined by gas-liquid chromatography. A nitrogen-specific detector is generally used. However, for small sample sizes (0.1 ml of plasma), an electron-capture detector may be utilized. With this detector measurements of concentrations as low as 0.02 nmol/g (5 ng/g) are still possible. The kinetics of the degradation of pirprofen to its pyrrole derivative were investigated. Plasma levels of pirprofen after a single oral dose of 400 mg in a healthy volunteer were measured by a method described previously as well as by the new method.

Adult↗
PubMed1984

Determination of the two mononitrate metabolites of isosorbide dinitrate in human plasma and urine by gas chromatography with electron-capture detection.

This paper describes a sensitive method for the determination of 2-isosorbide mononitrate and 5-isosorbide mononitrate as metabolites of isosorbide dinitrate at concentrations down to 2 ng/ml of 2-isosorbide mononitrate in both plasma and urine, and 5 ng/ml and 10 ng/ml of 5-isosorbide mononitrate in plasma and urine, respectively. The two mononitrate metabolites are extracted at basic pH into ethyl acetate, which is then evaporated to dryness. The residue is dissolved in a basic aqueous solution, which is washed with heptane and then re-extracted into ethyl acetate. The metabolites are quantitated by gas chromatography, using a 63Ni electron-capture detector. Conjugates of 2- and 5-isosorbide mononitrate are determined in urine after enzymatic hydrolysis.

Chemical Phenomena↗
PubMed1984

Oxprenolol placental transfer, plasma concentrations in newborns and passage into breast milk.

Thirty-two pregnant hypertensive patients were treated with oxprenolol administered in combination with dihydralazine as Trasipressol tablets. Before delivery, oxprenolol was demonstrable in the maternal plasma and the amniotic fluid. The free fraction of oxprenolol in the maternal serum (15% +/- 7.8; mean +/- s.d.; n = 25) was similar to that in normal serum. At the end of delivery, oxprenolol was found in both the maternal and umbilical plasma in most cases. Measurable, but low oxprenolol concentrations were present in the newborn plasma. After delivery, oxprenolol was demonstrable in the maternal plasma and breast milk. An infant weighing 3 kg and consuming 500 ml of breast milk per day would receive a maximum dose 60 times less than the normal daily dose for a hypertensive adult (4 mg/kg).

Adolescent↗
PubMed1983

Determination of isosorbide as a metabolite of isosorbide dinitrate in human urine by capillary gas chromatography with electron-capture detection.

A method for the determination of isosorbide as a metabolite of isosorbide dinitrate at concentrations down to 200 ng/ml in human urine is described. After addition of a known amount of isomannide as internal standard to 50 microliter of urine, both compounds are extracted at basic pH into chloroform-isopropanol (4:1, v/v), which is then evaporated to dryness. They are then derivatized with heptafluorobutyric anhydride, and isosorbide is quantitated by capillary gas chromatography with electron-capture detection. A conjugate of isosorbide is determined in urine after enzymatic hydrolysis.

Chromatography, Gas↗
PubMed1983

[Comparative elimination of pirprofen from the plasma and synovial fluid of the knee. 26 cases].

Twenty-six patients with various inflammatory diseases of the knee were treated with a 400 mg dose of pirprofen orally twice a day for 2 days. On the third day, samples of blood and synovial fluid were taken 3 h and 10 h approximately after a fifth 400 mg dose of the drug. Pirprofen concentrations, as determined by gas-liquid chromatography, were higher in plasma than in synovial fluid during the 2-5 h period post-dosing. They decreased with an elimination half-life of 6 h in plasma as against 41 hours in synovial fluid. This study demonstrates that pirprofen diffuses into the synovial fluid where it remains significantly longer than in plasma.

Adolescent↗
PubMed1983

Gas chromatographic determination of metoprolol in human plasma.

A method for the determination of metoprolol at concentrations down to 10 ng/ml in human plasma is described. After addition of oxprenolol as internal standard, both compounds are extracted into diethyl ether--dichloromethane (4:1, v/v) at basic pH, transferred into an acidic aqueous solution and back-extracted at basic pH into diethyl ether--dichloromethane. They are then derivatized with heptafluorobutyric anhydride. The derivatives are quantitatively determined by gas chromatography using a 63Ni electron-capture detector. The linearity was demonstrated, and the technique was formally validated in the concentration range 10-500 ng/ml. The technique was applied in a study of the bioavailability of metoprolol after oral administration to man; mean plasma concentrations are reported.

Biological Availability↗
PubMed1982

Biotransformation of tribenoside into benzoic acid in man.

In an experiment on three healthy volunteers, plasma levels of tribenoside and the elimination of benzoic acid in plasma and urine were followed up during a 7-day period of daily oral medication with tribenoside. Plasma levels of tribenoside, and plasma and urine concentrations of free and total benzoic acid were determined quantitatively. The concentrations of alpha- and beta-tribenosides found in the plasma were very low and did not increase during treatment. Total benzoic acid in the plasma remained at almost the same level during treatment as that observed before treatment. Biotransformation of tribenoside therefore does not appear to result in any significant change in the plasma concentrations of free or total benzoic acid. The average daily excretion of total benzoic acid in the urine of the 3 subjects was greater during treatment than before. The average increases in total benzoic excretion in the 3 subjects correspond to 23.5, 11.9, and 23.7% of the theoretical amount that would be produced by the metabolic oxidation of the 3 benzyl groups. This study demonstrates that tribenoside does not accumulate in plasma. Around 20% of the administered dose is metabolized to benzoic acid, which is almost entirely present in the body as hippuric acid. Hippuric acid is excreted at such a rate that it does not accumulate in plasma and does not exceed the normal concentration range.

Adult↗
PubMed1981

Gas chromatographic determination of phentolamine (Regitine) in human plasma and urine.

A method for the determination of unconjugated phentolamine at concentrations down to 5 ng/ml in human plasma, and of free and total (free plus conjugated) phentolamine down to 25 ng/ml in urine is described. After addition of 2-[N-(p-chlorophenyl)-N-(m-hydroxyphenyl)-aminomethyl]-2-imidazoline as internal standard, both compounds are extracted into benzene-ethyl acetate (1:1, v/v) at pH 10, transferred into an acidic aqueous solution and back-extracted at pH 10 into benzene-ethyl acetate. They are then derivatized with N-heptafluorobutyrylimidazole. The derivatives are determined by gas chromatography using a 63Ni electron-capture detector. In urine, total (free plus conjugated) phentolamine is determined after enzymatic hydrolysis. The technique was applied for the study of the plasma concentrations and urinary elimination after oral administration to man.

Arylsulfatases↗