CYP3A Polymorphism and Chronic Mercury Intoxication.

We analyzed the relationship between polymorphic loci of CYP3A genes (CYP3A4 (rs2740574), CYP3A5 (rs776746) and CYP3A7 (rs2257401)) with the development of chronic mercury intoxication. Of 170 men examined, 120 were workers chronically exposed to mercury vapors and 50 were carriers of GG-HSPA1B (+1267A/G) genotype associated with chronic mercury intoxication. Urinary content of 4-hydroxyantipyrine (4-HAP) generated in the reaction predominantly catalyzed by CYP3A4/CYP3A5 was studied in workers without chronic mercury intoxication (group 1, N=46) and patients in the delayed period of chronic mercury intoxication (group 2, N=74) depending on the genotypes of CYP3A4 and CYP3A5. For polymorphic loci CYP3A5 and CYP3A7, a tendency to an increase in the frequency of genotypes with rare alleles was found (p=0.071 and p=0.078) in the combined group (group 2 together with GGHSPA1B genotype carriers) relative to group 1. The high level of linkage disequilibrium was noted, especially for the pair rs776746 and rs2257401 (LD (r)=0.89). In group 2, a trend to 4-HAP decrease compared to group 1 (p=0.056 and p=0.065) was revealed for carriers of AA-CYP3A4 and GG-CYP3A5 genotypes. The involvement of CYP3A in the development of mercury neurotoxic effect remains unclear.

Impact of AhRR (565C > G) polymorphism on dioxin dependent CYP1A2 induction.

The current study uses the metabolic probe, antipyrine, and AhRR transcript expression (qRT-PCR) to examine the impact of the AhRR (565C > G or Pro185Ala, rs2292596) genetic polymorphism upon CYP1A2 inducibility in an established cohort of male firefighters with exposure to dioxin-like chemicals. The lipid adjusted concentrations of 29 dioxin and dioxin-like congeners were measured in serum. Possession of the G allele (CG and GG genotypes) was correlated with high expression AhRR transcript and lower CYP1A2 induction than found in individuals homozygous for CC. The induction of CYP1A2 was dioxin-dependent among carriers of the G allele. Multivariate models indicated that CYP1A2 activity, detected as urinary 3-hydroxymethylantipyrine, was significantly correlated with cotinine concentration and for those currently working as firefighters, dioxin body burden (ß = 0.54, p = 0.041). The efficacy of the AhRR in regulating the AhR signaling pathway is influenced by the AhRR (565C > G) polymorphism. Our study of firefighters using the induction of CYP1A2 as an indicator suggest that G allele proteins have variable AhR repressor activity which is manifested in a dioxin-dependent manner. These results provide evidence of metabolic differences that may affect susceptibility to dioxin-mediated health effects.

Impact of dioxins on antipyrine metabolism in firefighters.

Antipyrine (AP) metabolism was used to assess factors associated with the activity of hepatic oxidative enzymes in firefighters. Emphasis was placed on 3-hydroxymethylantipyrine (3HMAP), the metabolite with the greatest dependence on dioxin-inducible cytochrome P4501A2 (CYP1A2) activity. AP urinary metabolites were measured by HPLC in 38 male subjects from Eastern Siberia. Subjects were divided into three groups having similar ages and BMIs: current firefighters (n=11); former firefighters (n=17) and non-firefighters (n=10). Multiple regression models were constructed using the three major AP metabolites as a dependent variable to assess the influence of age, smoking as urinary cotinine concentration, dioxin exposure (as either WHO-TEQ or body burden), group, and CYP1A2*F (-163C>A) genotypes. Models for the proportion of dose excreted as the metabolite 3HMAP produced the best fit (adjusted R(2)=0.46, p<0.05). When the models were restricted to current firefighters, only those based on 3HMAP were statistically significant (adjusted R(2) of 0.80 (p<0.002)) due to contributions from urinary cotinine (ß=0.56, p<0.01) and dioxin expressed as body burden (ß=0.55, p=0.014). These results indicate that the antipyrine test can be used as metabolic probe of biological response to recent dioxin exposure provided the impact of smoking is carefully controlled.

Differential induction of cytochrome P450 isoforms and peroxisomal proliferation by cyfluthrin in male Wistar rats.

Cyfluthrin effects on in vivo drug metabolizing enzymes were evaluated using the oxidative substrate antipyrine. Antipyrine pharmacokinetics in plasma and urinary excretion of its major metabolites with and without cyfluthrin oral treatment (20mg/kg/day for 6 days) were investigated in rats. Cyfluthrin increased the apparent intrinsic clearance and decreased the antipyrine half-life at ß phase. Cyfluthrin also increased the clearance of the antipyrine metabolites, norantipyrine, 4-hydroxyantipyrine and 3-hydroxymethylantipyrine and the formation rate constants for each of the three metabolites measured in urine. These results suggest that cyfluthrin affects hepatic cytochrome P450 (CYP) system. In order to confirm, a second experiment was carried out. We evaluated the effects of repeated exposure to cyfluthrin on hepatic and renal CYP2E, CYP1A and CYP4A subfamilies and peroxisomal proliferation in rats following oral administration (10 and 20mg/kg/day for 6 days). At the highest dose, cyfluthrin increased renal and hepatic O-deethylation of ethoxyresorufin and O-demethylation of methoxyresorufin, metabolism mediated by the CYP1A subfamily. Liver and kidney were susceptible to cyfluthrin-dependent induction of 12- and 11-hydroxylation of lauric acid, suggesting CYP4A subfamily induction. Also cyfluthrin increased the ß-oxidation of palmitoyl-coenzyme A and carnitine acetyltransferase activity, supporting cyfluthrin as a peroxisome proliferator. In conclusion, the demonstration that cyfluthrin induced hepatic CYP1A, CYP4A subfamilies and peroxisomal proliferation raises the possibility of cyfluthrin could produce changes in oxidative stress.

Evaluation of the role of breast cancer resistance protein (BCRP/ABCG2) and multidrug resistance-associated protein 4 (MRP4/ABCC4) in the urinary excretion of sulfate and glucuronide metabolites of edaravone (MCI-186; 3-methyl-1-phenyl-2-pyrazolin-5-one).

Edaravone (MCI-186; 3-methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger, is used for the treatment of acute cerebral infarction. Edaravone is mainly excreted into the urine after conjugation to glucuronide or sulfate. Previous studies have demonstrated that edaravone sulfate is a good substrate of human organic anion transporter (OAT) 1 (SLC22A6) and human OAT3 (SLC22A8). In this study, we examined the involvement of breast cancer resistance protein [BCRP (ABCG2)] and [multidrug resistance-associated protein 4 MRP4 (ABCC4)] in the luminal efflux in the kidney. Increased ATP-dependent uptake of edaravone sulfate but not edaravone glucuronide was observed in BCRP-expressing membrane vesicles compared with control vesicles (Km = 16.5 microM). In contrast, edaravone glucuronide, but not edaravone sulfate, exhibited greater ATP-dependent uptake in MRP4-expressing membrane vesicles than that in control vesicles (Km = 9.85 microM). Unlike taurocholate uptake, S-methylglutathione had no effect on the ATP-dependent uptake of edaravone glucuronide by MRP4. The functional importance of BCRP and MRP4 in the urinary excretion of edaravone sulfate and edaravone glucuronide, respectively, was investigated using Bcrp and Mrp4 knockout mice. The renal clearance with respect to the kidney concentration of edaravone sulfate was reduced significantly but not abolished in Bcrp knockout mice compared with wild-type mice (3.62 versus 4.85 ml/min/kg b.wt.). The renal clearance of edaravone glucuronide was lower in Mrp4 knockout mice than wild-type mice (2.01 versus 5.06 ml/min/kg BW). Our results suggest that Bcrp and Mrp4 are partly involved in the luminal efflux of edaravone sulfate and edaravone glucuronide, respectively.

[Markers of impact and effects of dioxines in firemen who participated in fire extinguishing at "Irkutskcabel" plant].

The article contains data tracing connection between CYP1A2 activity, dioxines level and dioxine-sensitive genes expression in firemen who participated in fire extinguishing at cabel plant.

[Determination of nonmetabolized antipyrine in human urine]. / Metodika opredeleniia nemetabolizirovannogo antipirina v moche cheloveka.

A method for evaluating the renal clearance of antipyrine is proposed. The analyses were performed for a group of healthy females of reproductive age. The renal clearance of nontransformed antipyrine is found to be significant and the basic indices of renal activity (diuresis, creatinine excretion) are correlated with the drug concentration in saliva. A single administration of antipyrine in a dose of 10 mg/kg does not influence the renal function of healthy volunteers. The proposed photometric method of antipyrine determination in urine (under the conditions of loading with 0.5% NaCl solution at an amount of 0.5% of body weight) is sufficiently sensitive and provides information about the renal clearance of antipyrine, offering an important supplement to the data obtained by conventional methods.

[Experience of biologically active supplements to food containing indoles and isothiocyanates in patients with chronic viral hepatitis]. / Opyt ispol'zovaniia BAD k pishche, soderzhashchei indoly i izotiotsionaty, u bol'nykh khronicheskim virusnym gepatitom.

We have studied the effect of dietary supplement "ExPress" on clinical and biochemical parameters and on the activity of detoxification enzymes of liver in patients with chronic viral hepatitis B and C. 24 patients (19 females and 5 males aged 16-39 years) were enrolled in the study. Patients in case group received dietary supplement "ExPress" in addition to basic treatment. Average indices of total bilirubin in cases after treatment were 26.98 +/- 2.85 mmol/l, while in controls--34.31 +/- 5.72 mmol/l (p > 0.05). Average indices of alanin-aminotransferase and aspartate-aminotransferase were 78.75 +/- 11.25 and 160.75 +/- 23.67 units while in controls--208.5 +/- 56.4 and 330.25 +/- 65.14 units respectively (p < 0.05). In case group we observed full normalization of thymol test--from 9.99 +/- 1.51 to 4.03 +/- 0.73 units (p = 0.001), while in controls--from 7.9 +/- 1.56 only to 5.2 +/- 1.15 units (p = 0.194). Contents of non-metabolized antipyrine in cases decreased from 9.76 +/- 1.2% (p = 0.0002) whilst in controls--from 9.38 +/- 1.28% only to 3.93 +/- 1.18% (p = 0.01). Results of the study show that dietary supplement "ExPress" induces the activity of detoxification enzymes of liver and increases the efficiency of basic treatment.

Diabetes and elimination of antipyrine in man: an analysis of 298 patients classified by type of diabetes, age, sex, duration of disease and liver involvement.

UNLABELLED: Effects of diabetes on hepatic drug metabolism in man has not yet been adequately clarified. Two hundred ninety-eight diabetic patients, classified by type of the disease, age, gender, duration of therapy and liver involvement, were investigated. The antipyrine plasma clearance rate and cytochrome P450 content determinations in liver biopsies of subjects with diagnostic liver biopsy were used as indices of hepatic drug metabolising capacity. Drug metabolism was reduced as a function of age. Antipyrine elimination rate was dependent on the type of diabetes (type 1 versus type 2) and gender. Untreated type 1 patients eliminated antipyrine rapidly and insulin treatment normalised antipyrine elimination (clearance rates 89.5 +/- 20.3 versus 58.8 +/- 17.2 ml/min.; P<0.001). Males aged 16-59 years, but not over 60, who responded insufficiently to insulin therapy, had a rapid antipyrine elimination, which could be normalised by readjustment of insulin administration. Women with insufficient glucose control on insulin therapy had antipyrine elimination rate comparable to controls. Among type 2 diabetic patients, women metabolised antipyrine normally, but men over 40 years of age showed a reduced antipyrine metabolism. IN CONCLUSION: Drug metabolism in diabetes is affected by the type of disease, therapy and its effectiveness, and age and gender of the patients. These factors should be taken into account when evaluating overall drug metabolism in diabetic patients. This is especially important when investigating pharmacokinetics of new drugs for diabetic patients at different phases of the disease.

Urine antipyrine metabolites in rats with different resistance to hypoxia subjected to cold stress.

We studied antipyrine metabolism in rats with different resistance to hypoxia during adaptation to cold stress. Changes in the concentrations of some antipyrine metabolites at low temperature were associated with individual resistance to hypoxia. In low-resistant rats, antipyrine metabolism was suppressed from day 5 of cold exposure to day 3 of the recovery period. In highly resistant rats, antipyrine metabolism was inhibited on day 3 of cold exposure, but returned to normal on day 3 of the recovery period.

Direct nuclear magnetic resonance spectroscopic analysis of (13)C-labeled antipyrine metabolites in human urine.

Antipyrine is a useful probe to evaluate variation of in vivo activities of oxidative hepatic drug-metabolizing enzymes. Here we describe an approach using (13)C labeling and NMR spectroscopy for the direct and simultaneous analysis of major metabolites of antipyrine in human urine. [C-Methyl-(13)C]antipyrine (500 mg) was dosed orally to human volunteers, and the post-dose urine was analyzed by 100-MHz (13)C NMR spectroscopy under the conditions of distortionless enhancement by polarization transfer (DEPT) without any pretreatments such as deconjugation, chromatographic separation, or solvent extraction. Consequently, all the major metabolites in urine were successfully detected with favorable signal-to-noise ratios in the limited acquisition time (30 min). The reproducibility of the NMR detection was sufficient for the quantitative evaluation of the metabolic profile. A quantitative method is proposed using a combination of inverse gated decoupling and DEPT experiments with [2-(13)C]sodium acetate as an internal standard. The present approach is useful and practical to evaluate variation of in vivo activities of the conjugation enzymes as well as oxidative enzymes responsible for the formation of antipyrine metabolites in humans. This direct approach would enhance the value of the antipyrine test because of its simplicity and convenience.

Evaluation of the influence of diabetes mellitus on antipyrine metabolism and CYP1A2 and CYP2D6 activity.

STUDY OBJECTIVE: To evaluate the metabolism of antipyrine, a general metabolic probe, caffeine, a probe for cytochrome P450 (CYP) 1A2 and N-acetyltransferase activity, and dextromethorphan, a specific probe for CYP2D6 activity in patients with type 1 or 2 diabetes mellitus. DESIGN: Prospective, controlled study. SETTING: Research facility. Patients. Fifteen patients with type 1 and 16 with type 2 diabetes, and 16 healthy controls. INTERVENTION: Each subject simultaneously received antipyrine 10 mg/kg, caffeine 100 mg, and dextromethorphan 30 mg. MEASUREMENTS AND MAIN RESULTS: The pharmacokinetics of antipyrine and its primary metabolites were determined from saliva and urine samples. Type 1 diabetes had marked effects on antipyrine metabolism whereas type 2 disease did not alter the metabolism of any of the probe drugs. The apparent oral clearance of antipyrine was increased 72% in patients with type 1 disease compared with controls (p=0.0001). In addition, formation clearances of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine were increased by 74% and 137% in those patients relative to controls. The caffeine metabolic index (paraxanthine/caffeine) was increased 34% (p=0.11), and N-acetylation and CYP2D6 phenotype were not altered. CONCLUSION: The metabolism of antipyrine is increased in patients with type 1 diabetes. Based on in vitro reports of antipyrine metabolism and current caffeine metabolic index data, the predominant effect of type 1 diabetes appears to be an increase in CYP1A2 activity. Assessment of the effect of the disease on other specific CYP metabolic pathways is warranted.

Effect of experimental fasciolosis on antipyrine metabolism and clearance in water buffaloes.

The effect of chronic Fasciola hepatica infection on the metabolism of antipyrine, a marker of microsomal oxidative metabolism, was investigated in male water buffaloes dosed daily with 60 F. hepatica metacercariae over 20 days. The plasma elimination half-life of antipyrine was significantly elevated by 23% at 11 weeks postinfection (p.i.) but did not significantly differ from the control period at 20 weeks p.i. The systemic clearance of antipyrine decreased by 48% at 11 weeks p.i. and then returned to normal. The renal clearance for each of the main antipyrine metabolites decreased at 11 weeks p.i. (hydroxymethylantipyrine (HMA), -42%; norantipyrine (NORA), -58%; and 4-hydroxyantipyrine (OHA), -70%) and did not significantly differ from the control period at 20 weeks p.i. These findings indicate that experimental subclinical fasciolosis leads to altered antipyrine kinetics and to an inhibition of the different antipyrine metabolic pathways in water buffaloes.

Effect of fusidic acid on the hepatic cytochrome P450 enzyme system.

OBJECTIVE: To investigate the effects of fusidic acid therapy on the hepatic cytochrome P450 (CYP450) enzyme system. METHODS: Thirty HIV-seropositive L-methadone-substituted i.v. drug abusers (stage CDC/WHO B2 - 3 with CD4+-counts ranging from 65 to 293/microl) were randomized into 3 groups (A - C). Ten patients were treated with fusidic acid 500 mg/day over a period of 14 (group A) or 28 days (group B), respectively. Patients in group C served as a control group and did not receive any medication apart from L-methadone. In order to investigate the hepatic monooxygenase system, pharmacokinetics were determined in all patients before initiation and 14 and 28 days after starting therapy with fusidic acid. The concentration of antipyrine and its 3 main metabolites (norantipyrine (NORA), 4-hydroxyantipyrine (OHA), 3-hydroxymethylantipyrine (HMA)) in plasma and urine were measured by high-performance liquid chromatography (HPLC). RESULTS: No effects on antipyrine pharmacokinetics and pharmacokinetics of antipyrine metabolites were found in group A after 14 days of fusidic acid intake and in the control group without therapy. However, in contrast an activation of the CYP450 enzyme system was observed in group B after 28 days of fusidic acid therapy with an increase of total antipyrine clearance (43.0 +/- 7.62 ml/min to 51.0 +/- 9.03 ml/min) as well as clearances to all metabolites (NORA 7.11 +/- 1.75 to 8.60 +/-2.10 ml/min, OHA 11.5 +/- 2.89 to 14.0 +/- 3.97 ml/min, HMA 4.05 +/- 0.99 to 4.94 +/- 1.27 ml/min). Antipyrine half-life was significantly reduced (12.3 +/- 2.8 h to 9.4 +/- 2.2 h) and some patients developed clinical signs of L-methadone underdosage. CONCLUSIONS: Our results suggest that fusidic acid has a time-dependent activating effect on the CYP450 enzyme system. Especially in treatment of patients who are frequently under multidrug regimens such as HIV-positive patients drug interactions should be taken into consideration.

Changes in metabolism and urinary excretion of antipyrine induced by aerobic conditioning.

BACKGROUND: Physical conditioning has been reported to increase liver oxidative metabolism determined by antipyrine clearance. The purpose of this investigation was to study effects of aerobic conditioning on the different metabolic pathways of antipyrine by comparing the production clearances of antipyrine metabolites. PARTICIPANT: volunteers not engaged in the systematic practice of any sport (n = 14) were compared with aerobically-conditioned subjects (n = 14) (long distance runners, defined as men running > 80 km/week). INTERVENTIONS: antipyrine was administered orally. Saliva samples were collected under basal conditions and at 8, 16, 24, 32 and 40 hrs following antipyrine administration. Urine was collected for 24 hrs after antipyrine ingestion. MEASURES: endurance performance was expressed by the maximal oxygen uptake (VO2max), the ventilatory threshold and the 4 mM.l-1 lactate threshold (OBLA). Antipyrine pharmacokinetic parameters (antipyrine clearance and half-live) were obtained from saliva samples by the standard multiple-sample method. RESULTS: VO2max, ventilatory threshold and OBLA were higher in trained than in control subjects (+32%, +16% and +74%, respectively). Salivary antipyrine clearance was higher, whether or not this variable was corrected for weight (+26% and +38%, respectively), and antipyrine half-life was significantly reduced (-31%) in runners. There was no significant change with training in the renal clearance of antipyrine or in the norantipyrine (NORA) formation clearance but significant increases were observed in hydroxymethylantipyrine (HMA) and 4-hydroxyantipyrine (OHA) formation clearances (+42 and +37%, respectively). CONCLUSIONS: The findings indicate that aerobic conditioning leads to increased disposition of antipyrine and that the main metabolic pathways of the compound are changed differently.

Direct detection of antipyrine metabolites in rat urine by (13)C labeling and NMR spectroscopy.

Antipyrine is a useful probe to evaluate variation of in vivo activities of oxidative hepatic drug-metabolizing enzymes. Here we describe a new approach using (13)C labeling and NMR spectroscopy for the direct and simultaneous detection of all phase I and phase II metabolites of antipyrine in rat urine. [C-methyl-(13)C]Antipyrine was synthesized and administered orally to rats (100 mg/kg), and the 0- to 24-h postdose urine was analyzed by 100-MHz (13)C NMR spectroscopy under the conditions of distortionless enhancement by polarization transfer without any pretreatments such as deconjugation, chromatographic separation, and solvent extraction. Consequently, all the major metabolites in urine were successfully detected with favorable signal-to-noise ratios in the limited acquisition time (30 min). The assignments of the resonances were performed by enzymic modification and spiking authentic samples. The reproducibility of the NMR detection was sufficient for the quantitative evaluation of the metabolic profile. Effects of 3-methylcholanthrene on antipyrine metabolism were examined by this approach to evaluate variation of in vivo phase I and phase II metabolism of antipyrine in rats. The present approach is useful and practical to evaluate variation of in vivo activities of conjugation enzymes as well as oxidation enzymes responsible for the formation of antipyrine metabolites in rats. This direct approach would enhance the value of the antipyrine test because of the simplicity and convenience.

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.

[The effect of reversible ischemia of the rat liver on antipyrine metabolism and the isoenzyme activity of cytochrome P-450]. / Vliianie obratimoi ishemii pecheni krys na metabolizm antipirina i izofermentnuiu aktivnost' tsitokhromov P-450.

The character of changes in the metabolism of antipyrine, etoxy-, methoxy- and pentoxyresurphin after total reversible ischemia of the liver was studied in rats. In animals highly resistant to hypoxia the metabolism of xenobiotics specific to cytochromes P-450 IA1, IA2, and IIB1 was inhibited; in subjects with low resistance to hypoxia only P-450 and IA1 activity was suppressed while the activity of P-450 IIB1 and IA2 increased 2-3-fold.

Antipyrine pharmacokinetics and urinary excretion in female horses.

OBJECTIVE: To measure renal clearance of antipyrine and urinary excretion of antipyrine (AP) metabolites in horses by use of validated high-performance liquid chromatography (HPLC) methods. ANIMALS: 8 Standardbred mares. PROCEDURE: HPLC methods for measurement of AP in equine plasma and AP and its metabolites in equine urine were validated. Antipyrine (20 mg/kg of body weight) was administered i.v., and blood samples and urine specimens were collected over 24 hours. RESULTS: Median plasma clearance of AP in horses was 6.2 ml/min/kg, of which < 2% could be attributed to renal clearance. Urinary excretion of AP and its metabolites over 24 hours accounted for < 22% of the AP dose administered. The major metabolite of AP in urine was 4-hydroxyantipyrine. CONCLUSIONS AND CLINICAL RELEVANCE: Use of the proven validated methods for measuring AP and its metabolites indicated that AP has minimal renal clearance in horses, suggesting that plasma clearance of AP reflects hepatic clearance. Combined with AP metabolite data, the pharmacokinetics of AP may be useful for assessment of hepatic cytochrome P450 activity in horses.

The effect of age and sex on metabolism and urinary excretion of antipyrine.

BACKGROUND: Drug-metabolizing capacity is generally reduced in the elderly. The purpose of this investigation was to study antipyrine clearance and metabolite excretion in old subjects of both sexes. METHODS: Saliva clearance of antipyrine and the production clearances of antipyrine metabolites were studied in young and elderly volunteers of both sexes. Seventy-six elderly subjects (mean age 81 years) were compared with a group of 24 young subjects (mean age 29 years). RESULTS: After oral administration, salivary antipyrine clearance declined with age in both males and females, whether or not this variable was corrected for weight, and antipyrine half-life was significantly prolonged in elderly groups of either sex. The percentage urinary excretion of the antipyrine metabolites (hydroxymethylantipyrine, HMA; norantipyrine, NORA; and 4-hydroxyantipyrine, OHA) was reduced at 48 h in the elderly compared to young subjects by 23%, 31%, and 10%, respectively, in males, and by 41%, 41%, and 24%, respectively, in females. The formation clearance of HMA was reduced by 47% in males and by 52% in females. NORA clearance declined by 42 and 56%, respectively, in males and females. A decrease of 30% in males and 44% in females was observed in OHA clearance. CONCLUSIONS: The findings suggest that aging leads to altered disposition of antipyrine in both males and females and that the main metabolic pathways of the compound are not different in the elderly.