Konjugationsreaktionen im Arzneistoffwechsel der Ratte bei akuter �thanolbelastung

Isolation and characterization of the four antipyrine glucuronides and determination of their urinary excretion pattern in man by a reversed-phase h.p.l.c. assay

A large-scale procedure for the isolation of four urinary glucuronides in antipyrine metabolism is described; the isolated compounds are used as standards in a direct h.p.l.c. assay. The four glucuronides were characterized by u.v. and 1H-n.m.r. spectroscopy, and after hydrolysis by a t.l.c. assay of the corresponding aglycones. A reversed-phase h.p.l.c. assay procedure has been developed for the direct quantification of the four antipyrine glucuronides; this separates 3-hydroxymethyl-antipyrine glucuronide, 4,4'-dihydroxy-antipyrine glucuronide, norantipyrine glucuronide and 4-hydroxy-antipyrine glucuronide in a single run. Urinary elimination patterns of these glucuronides have been determined in five female and five male volunteers after antipyrine (1200 mg) administration. The direct assay of urinary glucuronides enables the simultaneous determination of glucuronidation activities and four different phase-I metabolites of antipyrine in vivo.

Investigations on antipyrine metabolism. II--Analysis of conjugated metabolites of antipyrine in rat and human urine by off-line combination of liquid chromatography and field desorption mass spectrometry

The complex pattern of conjugates in the metabolism of antipyrine in man and rat has been investigated using an off-line combination of liquid chromatography and field desorption mass spectrometry. Using this approach, field desorption mass spectrometry enables the direct identification of underivatized glucuronides and sulphates in antipyrine metabolism on the basis of the corresponding protonated or cationized molecules representing the base peaks in the field desorption mass spectra. All conjugated metabolites of antipyrine established so far--four glucuronides and three sulphates--were identified in extracts of urine after stepwise purification by column chromatography and subsequent mass spectrometric analysis.

Ethanol-induced increase in procainamide acetylation in man

1 The effect of ethanol on procainamide pharmacokinetics was studied in humans by two different experimental designs. In one, ethanol was given 1.5 h after taking the drug followed by hourly drinks, while in the other ethanol was given 2 h before and subsequently after taking the drug. 2 In both studies, ethanol caused a significant reduction of T1/2 and a significant increase in total clearance of procainamide, while the apparent volume of distribution of procainamide, as well as the renal clearance of both procainamide and N-acetylprocainamide were unaffected by ethanol treatment. 3 Ethanol treatment increased the percentage of N-acetylprocainamide measured in blood and urine and the ratio of AUCNAPA/AUCPA significantly. 4 The T1/2 and total clearance of procainamide was significantly different in slow and rapid acetylators.

Metabolism of 14C-antipyrine in suspensions of isolated rat liver cells

Suspensions of liver cells isolated from perfused rat livers were incubated with antipyrine-N-methyl-14C. Antipyrine was eliminated by first-order kinetics during incubations for 3 hours with primary suspensions (parenchymal cells + non-parenchymal cells) and suspensions of purified parenchymal cells. Antipyrine concentrations were unchanged when incubated with suspensions of non-parenchymal cells, dead cells or medium only. At the end of incubation period, 4-OH-antipyrine and 3-CH2OH-antipyrine were detected mainly as the glucuronide or sulphate conjugates, and evidence for the N-demethylation of antipyrine was also obtained. Half-lives for elimination of antipyrine in primary cell suspensions were not significantly different from the half-lives measured in parenchymal cell suspensions. This finding together with the lack of metabolism of antipyrine found in non-parenchymal cell suspensions suggest that oxidation and conjugation of antipyrine is mainly confined to the parenchymal cells. There was significant inhibition of antipyrine metabolism in primary suspensions by phenylbutazone (1.6 X 10(-3)M), dexamethasone (2 X 10(-4)M) and ethanol (1.3 X 10(-2)M, 0.75%). We suggest that the use of primary suspensions of isolated rat liver cells provide a rapid and simple method for the study of factors influencing drug metabolism in the liver.