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Quantitation and urinary pattern of 4,4'-dihydroxy-antipyrine, 4-hydroxy-antipyrine and 3-hydroxymethyl-antipyrine, as main metabolites of antipyrine in man and rat.

A t.l.c.-assay has been developed for the simultaneous determination from the urine of man and animals of three major hydroxylated metabolites of antipyrine (4,4'-dihydroxy-antipyrine, 4-hydroxy-antipyrine, 3-hydroxymethyl-antipyrine). The methodology is also applicable to bile fluid, liver perfusate and liver homogenate. Genuine conjugates are cleaved by acid hydrolysis and free, acid stable metabolites are extracted. Extracts are subjected to t.l.c. and the chromatograms analysed quantitatively by u.v.-reflectance measurements using authentic materials as standards. Calibration curves are linear with a correlation coefficient r greater than 0.990. Recovery for each metabolite is greater than 95%. Reproducibility of the method is good, with variation coefficients in the range of 3-7%, depending on concentration. The sensitivity of the method is sufficient for practical needs. The specificity of the procedure was confirmed using radio-labelled antipyrine. In man, 4-hydroxy-antipyrine is the principal hydroxylation product in this series, accounting for about 35-40% of the dose. 3-Hydroxymethyl-antipyrine makes up for about 13-17% and 4,4'-dihydroxy-antipyrine represents 3-6% of the dose of antipyrine. In the rat, 4-hydroxy-antipyrine accounts for about 15-31%, 3-hydroxymethyl-antipyrine for 22-28% and 4,4'-dihydroxy-antipyrine for up to 11-18% of the dose. Variation of this pattern in different strains is moderate. In both species, the major portion of phase-I metabolites is excreted as conjugates. Part of them appears in a free form.

Adult↗

Sex difference in antipyrine 3-hydroxylation. An in vivo-in vitro correlation of antipyrine metabolism in two rat strains.

Antipyrine metabolism depends on at least three isoenzymes of cytochrome P450 forming the main metabolites 3-OH-, 4-OH- and norantipyrine. We investigated to which extent antipyrine clearance and metabolite formation in vivo correlate with metabolite formation by microsomal fractions in vitro. The influence of sex was investigated in two rat strains. Antipyrine clearance in saliva was determined in 10-month-old Sprague-Dawley and Dark Agouti rats of either sex. Antipyrine and its metabolites in urine and microsomes were measured by a new HPLC method after solid phase or liquid extraction. Antipyrine clearance was 46% higher in males than in female rats. This was associated with a 40% higher urinary excretion of 3-OH-antipyrine in the male rats, the other metabolites being excreted to a similar extent. This higher production of 3-OH-antipyrine in vivo was paralleled by a higher intrinsic clearance in vitro while no sex difference in intrinsic clearance for the formation of the other metabolites was seen. The correlation between in vivo and in vitro metabolic clearance for 3-OH-antipyrine was good (r = 0.75) but unconvincing for 4-OH- (r = 0.49) and norantipyrine (r = 0.01). This could be due to further metabolism of 4-OH- and norantipyrine.

Animals↗

Effect of pregnenolone carbonitrile, promethazine and antipyrine pretreatment on antipyrine metabolite formation in rats.

The effect of three inducers of cytochrome P-450-mediated drug oxidations (Pregnenolone carbonitrile, promethazine and antipyrine) on antipyrine metabolite kinetics has been investigated using the urinary metabolite pattern and 14CO2 exhalation rate (CER)-time profile following [N-methyl-14C]antipyrine administration. The CER-time profiles showed the characteristic changes associated with induction, namely, increased maximum CER and decreased half-life, previously observed in phenobarbitone and beta-naphthaflavone-induced rats. Calculation of formation rate constants based on urinary recovery of 3-hydroxymethyl-, 4-hydroxy- and nor-antipyrine indicated no clear selectivity of induction by any pretreatment. However, the percentage increase of the latter two metabolites was two- to four-fold greater than for the former metabolite. The use of the metabolite ratio (3-hydroxymethylantipyrine/norantipyrine) is proposed to assess the qualitative nature of induction of antipyrine metabolism.

Animals↗

Liver blood flow, antipyrine clearance, and antipyrine metabolite formation clearance in patients with chronic active hepatitis and alcoholic cirrhosis.

Duplex scanning was used to measure liver blood flow (hepatic artery and main branches of the portal and hepatic veins) in six healthy subjects, five cirrhotic patients, and six hepatitis patients. Antipyrine clearance and formation clearances to its metabolites were also measured. Compared with healthy control subjects, cirrhotic patients had a lower hepatic vein blood flow (-76%, P < 0.05). This was due primarily to a lower portal vein blood flow (-36%, NS). A statistically significant difference in liver blood flow between patients with hepatitis and normal subjects was not detected. Antipyrine half-life, clearance, and the area under the serum drug concentration vs time curve were significantly different in cirrhotic patients compared with the healthy subjects (mean +/- s.d.-healthy controls: t1/2 = 13.7 +/- 3.0 h, CL = 30.0 +/- 8.6 ml h-1 kg-1, AUC = 549 +/- 139 mg l-1 h; cirrhotic patients: t1/2 = 32.4 +/- 1.7 h, CL = 12.3 +/- 2.1 ml h-1 kg-1, AUC = 1061 +/- 218 mg l-1 h; P < 0.008). Antipyrine half-life, clearance, and the area under the serum drug concentration vs time curve were not significantly different in hepatitis patients compared with the healthy subjects (hepatitis patients: t1/2 = 14.3 +/- 3.7 h, CL = 29.3 +/- 8.5 ml h-1 kg-1, AUC = 498 +/- 142 mg l-1 h). The volume of distribution of antipyrine was similar in all three groups of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

3-Hydroxymethyl antipyrine excretion in urine after an oral dose of antipyrine. A reconsideration of previously published data and synthesis of a pure reference substance.

Previously published data from this laboratory on the urinary excretion of 3-hydroxymethyl antipyrine (one of the major metabolites of antipyrine in man) have to be reconsidered, because of use of an impure reference substance in the high-pressure liquid chromatographic assay method. Comparison with newly synthesized, pure 3-hydroxymethyl antipyrine has shown that a correction factor of 0.45 needs to be applied to previously published data. Details of the synthesis of the pure reference 3-hydroxymethyl antipyrine are given.

Administration, Oral↗

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.

Adult↗

A comparative study of antipyrine pharmacokinetics in saliva and plasma using a colourimetric method of antipyrine analysis.

1. Half-life, apparent volume of distribution and metabolic clearance rate for antipyrine elimination were reliably estimated from either plasma or saliva samples. 2. Pharmacokinetic analysis of antipyrine from saliva utilizing a simple and sensitive colourimetric technique provided a convenient method for assessing the activity of hepatic microsomal drug-metabolizing enzymes.

Adult↗

Countercurrent exchange of progesterone and antipyrine between human utero-ovarian vessels, and of antipyrine between the femoral vessels in the cat.

The utero-ovarian vein and ovarian artery in surgical specimens were cannulated and perfused in a countercurrent manner with isotonic, buffered solutions, fortified on the venous side with progesterone or radiolabelled methylantipyrine. Both substances were gradually transferred from the vein into the artery in the majority of the experiments while albumin was not exchanged. The results point to the existence of a countercurrent exchange mechanism in the human ovarian pedicle. Hardly detectable amounts of methylantipyrine were transferred from femoral vein to artery in the cat.

Animals↗

The effect of sex on antipyrine metabolism in cattle at different ages.

The aim of this study was to determine the effect of sex on the metabolism of antipyrine by measuring the antipyrine plasma clearance as well as excretion of three major metabolites in urine in cattle of different ages. The experiment was carried out on 10 female and 10 male cattle of Black and White breed. The antipyrine test was carried out at 1, 2, 4, 6, 8, 12 and 18 months of age for each animal (single dose of 10 mg/kg antipyrine were given intravenously). The concentrations of antipyrine, 4-hydroxyantipyrine (4-OHA), 3-hydroxymethylantipyrine (HMA) and norantipyrine (NORA) were measured in plasma and urine by high performance liquid chromatography (HPLC). The apparent volume of distribution of antipyrine (aVd) decreased significantly between 1 and 18 months of age, but mean aVd values observed in males and females were not statistically different. The experimental period was characterised by a steady decrease (statistically significant) in antipyrine half-life (t1/2beta). These values did not differ significantly between males and females under 12 months. In 12 and 18 month-old animals the antipyrine half-life in the females was significantly shorter than in the males. The systemic clearance (Cls) of antipyrine increased significantly between 1 and 18 months of age. No significant differences were observed between systemic clearance of antipyrine in males and females under 12 months. In 12 and 18 month-old animals the Cls values were significantly higher in females than in males. Following intravenous administration, recovery of antipyrine and its three main metabolites increased significantly with age. These values did not differ significantly between males and females under 12 month of age. In 12 and 18 month-old females the excretion of 4-OHA and HMA in urine was significantly higher than in males at the same age. The excretion of NORA and unchanged antipyrine in males and females did not differ significantly. The partial clearances of antipyrine metabolites (Cl(m)) increased significantly between 1 and 18 months of age. No significant differences were observed between Cl(m) values in males and females under 12 months of age. In 12 and 18 month-old females the partial clearances of 4-OHA and HMA were significantly higher than in males. The clearance of NORA was significantly higher in 18 month-old females than in males. In conclusion, we report a sex-linked difference in plasma antipyrine clearance and urinary excretion of the main metabolites of antipyrine in cattle over 12 months of age, the females being the more active metabolizers.

Age Factors↗

Effects of atorvastatin, an HMG-CoA reductase inhibitor, on hepatic oxidative metabolism of antipyrine.

Possible effects of multiple-dose administration of atorvastatin on the pharmacokinetics of single-dose antipyrine were evaluated in this drug-drug interaction study. Twelve healthy male volunteers received three 200-mg capsules of antipyrine on days 1 and 22, and two 40-mg atorvastatin tablets in the morning on days 8 through 23. Serial blood and urine samples were collected after administration of each antipyrine dose. Plasma was analyzed for antipyrine, and urine samples were analyzed for antipyrine, 4-hydroxyantipyrine, and norantipyrine by validated high-performance liquid chromatography with ultraviolet detection. Overall, antipyrine and atorvastatin doses were well tolerated in healthy volunteers. Mean antipyrine concentrations in plasma after administration of a single, oral dose of antipyrine during coadministration of multiple doses of atorvastatin were nearly superimposible on concentrations after administration of antipyrine alone. Individual and mean parameter values for plasma pharmacokinetics of antipyrine were similar in both treatment periods. Atorvastatin did not significantly alter the fraction of clearance of antipyrine in plasma that occurred by urinary excretion of 4-hydroxyantipyrine and norantipyrine. These results indicate that the recommended highest daily dose of atorvastatin has negligible effects on antipyrine pharmacokinetics and on oxidative pathways responsible for the metabolism of antipyrine.

Administration, Oral↗

Antipyrine disposition in milk and saliva of lactating women.

Widely used to study hepatic drug metabolism, antipyrine rapidly distributes in total body water. Antipyrine distribution was studied in seven lactating women. Duration of lactation ranged from 2 to 19 mo. In all subjects the drug was rapidly absorbed; in five women peak concentrations were attained in milk and saliva by 1 hr and in the other two women by 3 hr (first point at which collections were made). In two women in whom antipyrine was measured at 10-min intervals during the first hour, peak concentrations in both milk and saliva were attained by 10 min after antipyrine. The time course for antipyrine disappearance from milk paralleled that from saliva for each subject. Antipyrine half-life (t1/2) varied from 5.6 to 20.3 hr for saliva (mean +/- SD = 11.5 +/- 4.8) and from 5.7 to 21.7 hr for milk (mean +/- SD = 11.6 +/- 5.4). In the two women with the shortest salivary antipyrine t1/2 (5.6 and 7.5 hr), antipyrine was readministered many months later, after they had stopped lactating. The salivary antipyrine t1/2 rose from 5.6 to 13.3 hr in one subject and from 7.5 to 14.6 hr in the other. The corresponding decrease in antipyrine clearance was 0.93 to 0.55 and 1.41 to 0.60 ml/min/kg. This observation suggests that in some subjects lactation may influence drug metabolism. The amount of antipyrine available to each nursing infant was estimated by assuming the the infant nursed 3 ounces every 4 hr for 24 hr after maternal antipyrine administration. The amount of antipyrine available to the nursing infant was calculated to range from 3.0 to 11.1 mg (mean +/- SD = 6.4 +/- 2.9 mg) or from 0.25% to 1.07% (mean +/- SD = 0.59 +/- 0.29%) of the maternal dose.

Adult↗