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 (β = 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.

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]

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]

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

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.

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.

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.

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.

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 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.

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.

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.

METHODS

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.

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]

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.

Influence of short-term water deprivation on antipyrine disposition in calves

The effect of four days water deprivation on the metabolism of antipyrine was studied in female Holstein-Friesian calves, aged 24 to 25 days, by measuring the antipyrine plasma clearance and the excretion of three major metabolites of antipyrine in urine. Water deprivation was associated with a statistically significant (P < 0.01) increase in the plasma antipyrine elimination half-life from 10.85(1.14) hours to 14.00(1.05) hours. In water deprived calves the systemic clearance of antipyrine was significantly (P < 0.05) decreased from 0.75(0.07) ml min-1 kg-1 to 0.56(0.05) ml min-1 kg-1. The excretion of three major metabolites of antipyrine: 4-hydroxyantipyrine, 3-hydroxymethylantipyrine and norantipyrine in urine was significantly (P < 0.01) decreased after water deprivation. In the control group no significant differences between the pharmacokinetic parameters of antipyrine in 24 to 25 and 28 to 29 day-old calves were observed. Also urinary profiles of antipyrine in calves from the control group did not differ significantly between 24 to 25 and 28 to 29 days of life. Our data indicate that water deprivation inhibits antipyrine elimination in calves.

Hepatic drug clearance in patients with mild cystic fibrosis

The plasma disposition of three model substrates (lorazepam, indocyanine green, and antipyrine) and the formation clearance of antipyrine metabolites (3-hydroxymethylantipyrine, norantipyrine, and 4-hydroxyantipyrine) were evaluated in 15 subjects with mild cystic fibrosis and in 15 healthy control subjects. Plasma clearance was significantly greater in patients with cystic fibrosis for both lorazepam (1.7 +/- 0.4 versus 1.2 +/- 0.5 ml/min/kg) and indocyanine green (14.2 +/- 6.1 versus 9.1 +/- 3.0 ml/min/kg). In contrast, the clearance of antipyrine was not significantly different (1.0 +/- 0.7 versus 0.8 +/- 0.3 ml/min/kg), but the formation clearance for 3-hydroxymethylantipyrine was significantly greater in patients with cystic fibrosis. Lorazepam and antipyrine apparent steady-state volume of distribution were not different between groups. These results suggest that clearance of drugs that undergo conjugation (e.g., lorazepam) or biliary excretion (e.g., indocyanine green) is increased in patients with mild cystic fibrosis. In contrast, the increased formation clearance of only one antipyrine metabolite suggests that alterations in clearance of drugs metabolized by cytochrome P450 enzymes are substrate specific and isoform specific in patients with cystic fibrosis.

Effect of age on the pharmacokinetics of antipyrine in calves

Single doses of 15 mg kg-1 antipyrine were given intravenously to 10 female calves of the black and white breed at one, two, four, six, eight and 12 weeks of age, and the concentrations of antipyrine, 4-hydroxyantipyrine (4-OHA), 3-hydroxymethyl-antipyrine (HMA) and norantipyrine (NORA) were measured in plasma and urine by high performance liquid chromatography. The first three months of life were characterised by a steady decrease in the apparent volume of distribution (aVd) and half-life (t0.5) of antipyrine. The systemic clearance (CIs) of antipyrine per unit bodyweight increased significantly between one and 12 weeks of age. Age did not influence the excretion of HMA and NORA in urine, but the excretion of 4-OHA by 12-week-old calves was significantly greater than by one-week-old calves. There was an age-related change in the partial clearances of the antipyrine metabolites when expressed per unit bodyweight.

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.

Absence of hepatic enzyme induction in prostate cancer patients receiving 'Casodex' (bicalutamide)

The potential for hepatic enzyme induction by bicalutamide ('Casodex') was assessed in an open study in prostate cancer patients. A single, oral dose of antipyrine 1000 mg was given before and after 12 weeks' bicalutamide therapy [once daily 50 mg (n = 7) or 150 mg (n = 11)] and its pharmacokinetics and metabolism were determined. Plasma or saliva samples were taken for the measurement of antipyrine concentration. Urine samples were assayed for antipyrine and its three major metabolites. With bicalutamide 50 mg, plasma antipyrine concentrations were maximal between 2 and 4 h after administration, declined in a log-linear manner and were unaffected by bicalutamide therapy; with bicalutamide 150 mg, saliva antipyrine concentrations were maximal between 2 and 4 h, declined in a log-linear manner, and were also unaffected by bicalutamide therapy. Antipyrine half-life was 16.3% shorter after bicalutamide 50 mg (p < 0.05); a small decrease (13.5%) in half-life after bicalutamide 150 mg was not statistically significant. A small reduction (18.6%, p < 0.05) in the AUCinfinity for antipyrine was noted after bicalutamide 150 mg. A statistically significant reduction in antipyrine recovery was seen with the lower bicalutamide dose (23.7%, p < 0.05). The statistically significant changes were small in absolute terms and showed no dose-response relationship. Bicalutamide does not significantly induce the hepatic enzymes responsible for antipyrine metabolism and has no obvious potential for producing clinically significant drug interactions due to enzyme induction.

The influence of dietary restriction on the metabolism of theophylline and antipyrine in the ageing female BN/BiRij rat

The influence of ageing and dietary restriction (DR) on the in vivo activities of different P450 enzymes was studied longitudinally in female BN/BiRij rats. For this purpose, antipyrine (AP) and theophylline (TH) were used as substrates. The metabolic clearances of AP (CIm AP) and TH (CIm TH) were used as indicators for P450 enzyme activities in vivo. Therefore, we also included the assessment of the clearances of formation of three AP metabolites, i.e., 3-hydroxymethylantipyrine (CI-->HMA), 4-hydroxyantipyrine (CI-->OHA) and norantipyrine (CI-->NORA). Ninety, 50 and 10% survival times were prolonged significantly in DR rats. In control animals, the contribution to the metabolism of AP in the formation of HMA, OHA and NORA, expressed as percentage of the dose, decreased with ageing, indicating that other pathways compensate for this decrease. Only a significant decrease in the metabolism to OHA was observed in DR animals. CI-->HMA, CI-->OHA and CI-->NORA showed an age-related decrease in the control rats, whereas in the DR rats an age-related decrease was observed for CI-->HMA and CI-->OHA. The results of the present study suggest that the decrease in the activities of the P450 enzymes involved in the formation of HMA, OHA and NORA have a later onset in the DR rats. In conclusion, DR not only has a strong positive influence on the health and life span of the rats, but also results in a delayed onset of the decrease in activity of certain P450 enzymes.

Effects of flumethrin on hepatic drug-metabolizing enzymes and antipyrine disposition in rats

The effects of repeated exposure to the pyrethroid insecticide flumethrin (40 mg/kg intraperitoneally once a day for 6 days) on the activity of cytochrome P450-dependent monooxygenases and UDP-glucuronosyltransferase as well as on antipyrine disposition were investigated in male Wistar rats. Pretreatment with flumethrin decreased the activities of NADPH-cytochrome c reductase (38%), aniline hydroxylase (53%), aminopyrine N-demethylase (54%), and UDP-glucuronosyltransferase (34%), and the content of cytochrome P450 (36%) in hepatic microsomes. Total plasma clearance of antipyrine was decreased by flumethrin pretreatment (54%), while the elimination half-life at beta phase and the mean residence time of antipyrine were increased (96 and 88%, respectively). Urinary excretion of norantipyrine, 4-hydroxyantipyrine, and 3-hydroxymethylantipyrine was decreased by 60, 38, and 33%, respectively, in the 96 hr after flumethrin treatment. In addition, the rate constants for formation of each of these metabolites were decreased by an average of approximately 74%. These findings provide evidence that flumethrin exposure diminishes hepatic enzyme levels and catalytic activities of monooxygenase systems as well as oxidative metabolism of antipyrine.

Separation and identification of phase I and phase II [14C]antipyrine metabolites in rat and dog urine

A simple and accurate HPLC procedure was developed to quantify, in a single run, all phase I and phase II [14C]antipyrine metabolites that occur in rat and dog urine. All metabolites were subjected to thermospray-LC-MS and EI-MS in order to establish their structure. The rat metabolizes antipyrine to eight major metabolites, six of which are conjugated; 1.4% of the dose was excreted unchanged, 18.9% in a free form, 30.6% as sulfates and 21.1% as glucuronides. The dog metabolizes antipyrine to four metabolites, all as sulfate (61.0% of the dose) or glucuronide conjugates (16.2% of the dose).

The effect of zileuton on antipyrine and indocyanine green disposition

The effects of single and multiple oral doses of zileuton on the pharmacokinetics of antipyrine and indocyanine green were studied in 16 healthy, nonsmoking adult men by means of a double-blind, randomized, parallel placebo-controlled design. Indocyanine green disposition was not significantly altered by zileuton. Plasma antipyrine clearance declined by 20% (p < 0.0005) and 52% (p < 0.0005) after single and multiple dose zileuton exposure, respectively. Total urinary recovery of unchanged antipyrine and metabolites decreased with zileuton exposure. Selective declines from baseline of 16% (p = 0.007) and 20% (p = 0.003) after single-dose zileuton and 30% (p < 0.0005) and 43% (p < 0.0005) after multiple-dose zileuton were detected in recovery of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine, respectively. Urinary recovery of the N-demethylantipyrine metabolite norantipyrine and percent of conjugation of 3-hydroxymethylantipyrine were unchanged by zileuton. In conclusion, zileuton therapy has no detectable effect on indocyanine green disposition but exerts marked effects on antipyrine plasma and urine metabolite disposition.

Antipyrine clearance and metabolite excretion in patients with chronic hepatitis C

BACKGROUND/AIMS

Our aim was to study whether chronic hepatitis C affects the three metabolic pathways of the model drug antipyrine differently.

METHODS

We measured antipyrine clearance from saliva as well as urinary excretion of its main metabolites 4-hydroxy-antipyrine, 3-hydroxy-methyl-antipyrine, and nor-antipyrine in 24 patients with chronic hepatitis C and in 21 healthy control subjects. Due to incomplete urine collection, 12 liver patients and three controls were excluded.

RESULTS

Antipyrine clearance (mean +/- SD) was significantly lower in patients with chronic hepatitis C, 1.2 +/- 0.7 l.h-1 (n = 12), than in controls (n = 18), 2.2 +/- 1.0 l.h-1 (p = 0.006). The urinary excretion of each of the metabolites was depressed to an equal extent in liver patients. The severity of the liver disease, as assessed by Child Pugh score, serum albumin and bilirubin, correlated significantly with antipyrine clearance and urinary excretion of the metabolite 3-hydroxy-methyl-antipyrine. The hepatitis activity index (Knodell) correlated with 3-hydroxy-methyl-antipyrine and 4-hydroxy-antipyrine, only.

CONCLUSIONS

Moderate-severe chronic hepatitis C does not seem to depress the three main metabolic pathways of antipyrine differently.

Elimination studies of antipyrine and its metabolites in healthy Saudi Arabians

1. We measured the antipyrine clearance in 18 healthy Saudi subjects and determined the urinary excretion of three of its metabolites: 4-hydroxyantipyrine (4-OH AP), norantipyrine (NOR AP) and 3 hydroxymethylantipyrine (3-OHM AP) in 21 subjects. 2. The mean +/- SD of the antipyrine clearance was 2.4 +/- 1.1 h-1 (range 1.0-5.5 l h-1) and the corresponding value per kg body weight was 0.6 +/- 0.2 ml min-1 kg-1. Urinary excretion of antipyrine (AP), 4-OH AP, NOR AP and 3-OHM AP expressed as a percentage of the oral dose of antipyrine given was 2.8 +/- 2.2, 14.5 +/- 6.9, 12.3 +/- 5.6 and 7.6 +/- 3.2 respectively. 3. Compared to Africans, Saudis preferentially metabolize AP to NOR AP and compared to Caucasians to 3-OHM AP, rather than to 4-OH AP. These discrepancies may reflect age differences between the study populations rather than genetic or ethnic variations.

Elimination of antipyrine and its metabolites in interferon treated hepatitis C

1. To study the effect of interferon on hepatic drug metabolism in chronic hepatitis C, we examined nine patients before and at the end of 6 months of interferon treatment. 2. Routine liver function was determined together with the salivary clearance of antipyrine and the 48 h urinary excretion of the main metabolites of antipyrine: 4-hydroxyantipyrine, 3-hydroxymethylantipyrine and norantipyrine before and after 6 months of interferon treatment. 3. Liver pathology, routine liver function, and antipyrine metabolism remained unchanged after patients were treated for 6 months with interferon for a histologically advanced but clinically compensated chronic hepatitis C.

Isolation and purification of three glucuronides of antipyrine. Proposal for an original analytical method for quantitation of sulpho- and glucuroconjugated metabolites

The determination of the concentrations of antipyrine metabolites in biological fluids is hampered by the difficulty in obtaining pure conjugated compounds to be used as standards. Most authors have proposed determination of total forms by high performance liquid chromatography (HPLC) after deconjugation of these metabolites using chemical or enzymatic hydrolysis. Up to now there is no satisfactory hydrolysis method for the study of all antipyrine metabolites. The situation is further complicated by the fact that the deconjugated metabolites are highly unstable whichever technique is being used. Because of the lack of stability of all these molecules it has been necessary to isolate the glucuroconjugated compounds from urine. We describe a method which allows us to obtain highly purified glucuroconjugated metabolites of antipyrine. Sulphoconjugated compounds have been synthesized previously. We are thus able to propose a chromatographic procedure which allows us to determine simultaneously all stable phase I and phase II metabolites of antipyrine in biological fluids without any step of extraction. This analytical technique allows us to study the activity of the different isoenzymes implicated in the metabolism of antipyrine.

Metabolism of antipyrine in vivo in two rat models of liver cirrhosis. Its relationship to intrinsic clearance in vitro and microsomal membrane lipid composition

Antipyrine metabolism depends on at least three isoenzymes of cytochrome P450 forming the main metabolites 3-OH-, 4-OH- and norantipyrine. We investigated to what extent antipyrine clearance and metabolite formation are impaired in two models of liver cirrhosis in the rat, namely micronodular cirrhosis induced by chronic exposure to phenobarbital/CCl4 and biliary cirrhosis induced by bile duct ligation. Salivary antipyrine clearance was decreased to a similar extent in cirrhosis induced by CCl4 and bile duct ligation (-35%). Clearance for production of 3-OH-antipyrine was decreased in both models, while 4-hydroxylation was maintained. Metabolic clearance of both 3-OH-antipyrine and 4-OH-antipyrine in vivo correlated with their clearance in vitro (r = 0.658 and r = 0.583) but not with that of norantipyrine. The microsomal cholesterol content was increased by 16% and 90% in CCl4 and bile duct-ligated cirrhotic rats (P < 0.001), respectively. Membrane fluidity, expressed as the ratio of phospholipids to cholesterol, correlated with the in vivo clearance for production of norantipyrine (r = 0.841) but not of 3-OH- or 4-OH-antipyrine, while clearance in vitro was not related to altered lipid composition. Our results demonstrate that the cytochrome P450 isoenzymes responsible for the different pathways of antipyrine metabolism are affected to different extents by cirrhosis. Alterations in intrinsic clearance explain only part of the loss of hepatocellular function. Altered lipid composition contributes to this loss of function but other factors, among them loss of hepatocytes and changes in microcirculation, could be more important determinants of the decrease in xenobiotic metabolism in cirrhosis.

Investigation of the human metabolism of antipyrine using coupled liquid chromatography and nuclear magnetic resonance spectroscopy of urine

The potential of coupled high-performance liquid chromatography-nuclear magnetic resonance spectroscopy for the detection and identification of drug metabolites has been investigated by direct analysis of human urine collected following administration of antipyrine. This approach provided a rapid method of characterizing the major human urinary metabolites of this drug and promises to be of widespread value in structural studies of xenobiotic metabolites.

The relationship between phenazone (antipyrine) metabolite formation and theophylline metabolism in healthy and frail elderly women

The influence of aging on the metabolism of phenazone (antipyrine), and the relationship between the formation of 3 phenazone metabolites and the metabolic clearance of theophylline in healthy and frail elderly women, were examined. Whereas the elimination half-life did not change, clearance of phenazone decreased by about 50% with age in healthy women receiving phenazone without theophylline. However, the summation of the urinary recovery of phenazone and the measured metabolites, expressed as percentage of the phenazone dose, was lower in the healthy elderly (37 +/- 9% vs 74 +/- 15%). In both healthy and frail females the clearance of formation of 4-hydroxy-phenazone and the metabolic clearance of theophylline correlated strongly (r = 0.93 and 0.90, respectively). In non-healthy elderly females, strong correlations were also observed between the other metabolic pathways of phenazone and the metabolic clearance of theophylline. Coadministration of theophylline in the elderly increased the percentage of the phenazone dose excreted as the measured metabolites. A considerably higher interindividual variability in the disposition of phenazone and theophylline was observed in the frail elderly women. This high degree of variability in drug metabolism may be one of the explanations for the problems often occurring after drug prescription in the elderly.

Non-induction of extrahepatic antipyrine and metronidazole metabolism evaluated from partially hepatectomized rats

1. The effect of beta-naphthoflavone (BNF), given i.p. (n = 9) and orally (n = 9), on the metabolism of antipyrine and metronidazole was investigated in rats. 2. The clearances of antipyrine and metronidazole were determined on a single saliva sample. The rates of formation of antipyrine and metronidazole metabolites were determined from a 20 h urine sample and saliva clearance. 3. Administration of beta-naphthoflavone i.p. was significantly more effective than oral dosage on the induction of antipyrine and metronidazole metabolism (p < 0.05). 4. The capacity of extrahepatic tissues to metabolize antipyrine and metronidazole was quantitatively assessed in rats with and without pretreatment with beta-naphthoflavone immediately after sham operation or 70% partial hepatectomy (n = 40). 5. Antipyrine and metronidazole clearances correlated with liver weight in induced and non-induced rats. Linear regression of antipyrine and metronidazole clearances did show a non-significant Y-intercept (p > 0.05), indicating a negligible extrahepatic metabolism in both induced and in non-induced rats. 6. From a quantitative point of view this study indicates that induction of extrahepatic cytochrome P450 metabolism of antipyrine and metronidazole is negligible.

Solid phase extraction and simultaneous high performance liquid chromatographic determination of antipyrine and its major metabolites in urine

A reversed phase gradient high performance liquid chromatographic method utilizing solid phase extraction has been described for the simultaneous determination of antipyrine (AP), 4-hydroxyantipyrine (4-OHAP), norantipyrine (NorAP) and 3-hydroxymethylantipyrine (3-OHMAP) in human urine after hydrolysis with beta-glucuronidase. The C-18 sorbent cartridges were conditioned and urine samples were applied, washed with 1 x 4 mL of phosphate buffer and eluted with 3 x 100 microL of 20% v/v of acetonitrile in methylene chloride. The eluent was evaporated to dryness, reconstituted in 100 microL phosphate buffer and injected. The calibration ranges were 2.0-250 micrograms/mL (AP), 2.5-250 micrograms/mL (NorAP), 2.0-250 micrograms/mL (3-OHMAP) and 5.0-500 micrograms/mL (4-OHAP) with regression coefficients of 0.998 or greater. Specificity was indicated by the absence of interferences in chromatogram of blank urine from normal as well as cirrhotic patients. The average recovery was 86.7% for AP, 90.5% for NorAP, 85.2% for 4-OHAP and 74.2% for 3-OHMAP. The within-assay precision as indicated by the reproducibility of the assayed spiked urine was less than 9% in all cases and the between-assay precision was less than 12%. The method was applied to studies on antipyrine metabolism in stable cirrhotic patients. Following administration of a single oral dose of about 1000 mg to nine stable cirrhotic patients and eight age-matched healthy volunteers, the cumulative account excreted in the urine up to 48 h for AP and the three metabolites was comparable to other literature reports.

Separation and identification of the 4-hydroxyantipyrine sulphoconjugate

In a previous study we observed, during separation of total antipyrine metabolites by high-performance liquid chromatography and after enzymatic hydrolysis, an unidentified peak corresponding to an ionic compound with pyrazolinone features. In the present study, this compound was identified as the 4-hydroxyantipyrine sulphoconjugate, and its structure was definitively confirmed by gas chromatographic-mass spectrometric analysis and by the use of pure synthetic substance. We also demonstrated the inhibitory effect of sodium metabisulphite, a necessary preservative of urinary samples, on hydrolysis of this conjugate in the presence of sulphatases from Helix pomatia or Aerobacter aerogenes. This inhibitory effect makes it impossible to perform a global assay of antipyrine metabolites after enzymatic or chemical hydrolysis and confirms the value of direct assay of the 4-hydroxyantipyrine sulphoconjugate.

The effect of diltiazem on hepatic drug oxidation assessed by antipyrine and trimethadione

The effect of pretreatment for 3 days with diltiazem 60 mg three times a day on the pharmacokinetics of 500-mg antipyrine and 250-mg trimethadione was studied in six healthy male subjects. Diltiazem decreased the total body clearance from 34.0 +/- 8.0 to 28.6 +/- 6.1 mL/min (P less than .01), and prolonged the elimination half-life from 12.6 +/- 3.0 to 14.3 +/- 2.5 hours (P less than .01) of antipyrine without any changes in volume of distribution. The cumulative renal excretion (% dose) of antipyrine was significantly increased from 2.23 +/- 0.73 to 2.78 +/- 0.83% (P less than .05). Clearances of production for three major antipyrine metabolites, norantipyrine (4.31 +/- 1.64 to 3.50 +/- 1.28 mL/min, P less than .01), 3-hydroxymethylantipyrine (4.67 +/- 1.63 to 3.82 +/- 1.34 mL/min, P less than .01) and 4-hydroxyantipyrine (10.47 +/- 3.41 to 8.16 +/- 2.82 mL/min, P less than .01) were reduced significantly by diltiazem. On the other hand, diltiazem did not produce any significant changes in pharmacokinetic parameters of trimethadione and plasma concentration ratio, oxidative major metabolite of trimethadione to trimethadione itself. These results suggest that other drugs metabolizing the same hepatic oxidative pathways as antipyrine, may be influenced by diltiazem.

The pharmacokinetics of antipyrine and three of its metabolites in the rabbit: intravenous administration of pure metabolites

Antipyrine (AP) is a commonly used probe of oxidative metabolism. Indirect evidence demonstrates formation rate limited disposition of its metabolites. Kinetic studies using antipyrine and its major metabolites 3-hydroxymethylantipyrine (HMA), norantipyrine (NORA), and 4-hydroxyantipyrine (OHA) were completed to investigate the metabolic fate of preformed antipyrine metabolite and to demonstrate directly formation rate-limited metabolite disposition in vivo. Bolus injections of antipyrine and preformed metabolites (40-50 mg/kg) were administered to male, New Zealand white rabbits. Plasma and urine were analyzed using HPLC. These studies demonstrate that HMA, NORA, and OHA are formation rate limited in the rabbit. NORA appears to undergo further extensive oxidative and conjugative metabolism. Unknown additional peaks were detected in urine after NORA dosing but not after HMA or OHA administration. Mass spectroscopy of the unknown HPLC eluents identified potential structures of these NORA metabolites.

Species- and sex-related differences in the plasma clearance and metabolite formation of antipyrine. A comparative study in four animal species: cattle, goat, rat and rabbit

1. The plasma disposition of antipyrine, and its urinary metabolite pattern, were studied in both sexes of four animal species: rat, dwarf goat, rabbit and cattle. 2. No sex differences in plasma elimination of antipyrine were found in rabbit and goat; however, in rat and cattle the effect of sex was marked. As expected, male rat showed a higher plasma clearance value than female. In contrast bulls showed a significantly lower clearance value than cows. 3. Metabolite patterns varied widely from one species to another. The major urinary metabolite in rabbit and the two ruminant species was 4-hydroxy-antipyrine (OHA), whereas in rat 3-hydroxymethylantipyrine (HMA) was quantitatively the most important metabolite. 4. HMA was excreted in the 24 h urine in larger amounts by male rats than by females. Metabolism of antipyrine to HMA was also sexually different in the dwarf goat, but in this species females were more active than males. The effect of sex on the metabolite pattern in cattle was marked. 5. It is concluded that in ruminants there may be xenobiotic metabolic pathways which are under hormonal control, just as there are in rats and mice. If hormones influence drug metabolism in food-producing animals, residue levels of xenobiotics or their metabolites in food from animal origin may differ with the sex of the animal, or may be altered after treatment with anabolic hormones.

Cytochrome P-450 isozyme pattern is related to individual susceptibility to diethylnitrosamine-induced liver cancer in rats

Differences in susceptibility to chemical carcinogenesis between rodent strains and species have been linked to variations in genetically-determined mixed function oxidase activities. In order to verify whether such variations also determine the susceptibility of individual animals of the same strain to a chemical carcinogen, outbred male Wistar rats were administered diethylnitrosamine (DEN) (1, 2, or 3 mg/kg) five times a week for 20 weeks. The relationship was examined between the outcome (i.e., presence or absence of liver tumors, and latency period) and the hepatic activities of mixed function oxidases and conjugating enzymes, as well as of O6-methylguanine-DNA-methyltransferase, measured before the carcinogen treatment. In addition, the metabolic profiles of two model drugs, antipyrine and disopyramide, in the urine were analyzed and correlated with the carcinogen susceptibility. The length of the latency period of hepatocellular tumors in individual rats was negatively related to the activities of hepatic dimethylnitrosamine N-demethylase, aryl hydrocarbon hydroxylase and epoxide hydrolase and positively related to the amount of microsomal protein. Consistent relationships between the other 10 measured parameters and the susceptibility to DEN-induced carcinogenesis were not detected. Long-term treatment with DEN slightly decreased the proportion of metabolism of antipyrine into norantipyrine, and increased the share of 4-hydroxyantipyrine; a decrease in the metabolism of disopyramide to N-deisopropyldisopyramide was also detected. It is concluded that the pattern of cytochrome P-450 isoenzymes is related to differences in individual susceptibility to nitrosamine-induced carcinogenesis. The relationship was most marked at low dose levels, which are the levels at which nitrosamine exposures of humans are known to occur.

High-performance liquid chromatographic method for the determination of the three main oxidative and 3-carboxylic antipyrine metabolites in human urine

The oxidative metabolism of xenobiotics is usually explored using the antipyrine test, which consists of determining the production clearances and urinary percentages of three major antipyrine metabolites 4-hydroxyantipyrine, norantipyrine and 3-hydroxymethylantipyrine. The total forms of these compounds are generally determined by high-performance liquid chromatography (HPLC). However, the 3-carboxylic acid metabolite (3-carboxyantipyrine), which is the ultimate oxidation form in the 3-hydroxylation pathway, should also be taken into account, but so far its determination by HPLC has not been reported. A simple and accurate HPLC method has now been developed to determine the three major metabolites plus 3-carboxyantipyrine. In this method, all compounds are extracted in an aprotic non-polar solvent, at pH 3.5 for the major metabolites and unchanged antipyrine, then at pH 0.9 for 3-carboxyantipyrine. Total forms are evaluated after enzymatic hydrolysis. Throughout the procedure, attention is paid to the relative instability of norantipyrine and 4-hydroxyantipyrine. Recovery, accuracy and precision are discussed. The method has been applied to the determination of relative amounts (percentage of the dose administered) excreted in the urine of ten adult subjects 48 h after ingestion of antipyrine (600 mg). The proportion of 3-carboxyantipyrine excreted was 4.5 +/- 0.2%, which is in agreement with published values obtained by gas chromatography. The excretion rates of the major metabolites also were similar to those reported in the literature, thereby confirming that the reported method is valid. 3-Carboxyantipyrine is totally excreted as the free form and norantipyrine almost completely as glucuroconjugate.

Influence of subject age on the inhibition of oxidative metabolism by ciprofloxacin

Case reports suggest that the magnitude of inhibition of oxidative metabolism produced by ciprofloxacin may be greater in elderly subjects. We examined the effect of oral ciprofloxacin on antipyrine disposition in 13 young (ages, 23 to 34 years) and 9 elderly (ages, 65 to 82 years) healthy volunteers. Ciprofloxacin decreased antipyrine oral clearance in young and elderly subjects (P less than 0.05), with the average decreases being similar in both groups (23.3% for the young subjects and 27.9% for the elderly subjects). Ciprofloxacin concentrations in serum were significantly higher (mean, 57%) in the elderly. The formation clearance of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine was also significantly decreased in both groups of subjects; however, norantipyrine formation, accounting for 15 to 20% of antipyrine clearance, was reduced only in the elderly. These results suggest that elderly subjects are not more sensitive to the inhibitory effect of ciprofloxacin on antipyrine metabolism. However, careful clinical monitoring is necessary with all patients, irrespective of age, taking ciprofloxacin concomitantly with drugs primarily eliminated by the cytochrome P-450 system.

Lack of effect of halofantrine on hepatic drug metabolism in the rat in vivo and in vitro

The effect of the antimalarial drug halofantrine (Hf) on hepatic drug metabolism in the rat has been studied in vivo and in vitro using different model drug substrates. Hf in vitro produced no significant effect on the values of Km and Vmax for aminopyrine N-demethylation or 7-ethoxycoumarin O-dealkylation in microsomes incubated with Hf (0.01-0.1 mM) or on the rate of N-demethylation of aminopyrine or O-dealkylation of Ec in microsomes produced from rats dosed chronically with Hf (200 mg/kg) for 4 days. The disposition of antipyrine (Ap) was investigated in the isolated perfused rat liver preparation (IPRL). Following the administration of bolus doses of Hf (0.5, 2.5 and 5.0 mg) no significant changes were observed in the half-life (t1/2), clearance (Cl) or apparent volume of distribution (Vd) for Ap compared with controls. Pentobarbitone induced sleeping time was also assessed in mice. No significant difference was determined in time to recovery of the righting reflex for mice receiving Hf as single oral doses or chronically over 4 days when compared with appropriate controls. The potential for selective isoenzyme effects was studied in vivo. The three principal urinary metabolites of Ap, norantipyrine (Np), 3-OH and 4-OH Ap were measured in rat urine, with no significant change in urinary recovery of Ap or any of the metabolites in the presence of Hf (1.25 mg/kg i.p.) compared with controls. These results suggest that Hf is not, in contrast to many commonly used quinoline antimalarials, a potent or specific inhibitor of drug metabolism in vitro or in vivo.

[The effect of diethylnicotinamide (cordiamine) on the activity of the hydroxylating and glucuronyl-conjugating systems in humans]

Administration of diethylnicotinamide (250 mg orally three times for 8 days) to healthy subjects increased antipyrine (AP) elimination from the saliva by 23% and decreased its half-life by 26%. The excretion in the urine of the products of AP hydroxylation 3-carboxymethylantipyrine and nor-antipyrine as well as glucuronides 3-hydroxymethylantipyrine increased. A positive correlation between the dynamics of the excretion of antipyrine metabolites and glucuronic acid was observed. The elimination from blood of bilirubin glucuronides increased. Diethylnicotinamide in therapeutic doses is supposed to stimulate the processes of hydroxylation and glucuronyl conjugation in humans.

Evaluation of cytochrome P-450 mediated metabolism of antipyrine in the rat at different extents of fluosol-DA hemodilution

Two reports of antipyrine disposition in rats after hemodilution with 20, 40, or 80 ml/kg of Fluosol-DA are evaluated to determine if the extent of hemodilution influenced cytochrome P-450 mediated antipyrine metabolism. Alterations in antipyrine clearance (Cl) and 3-hydroxymethylantipyrine (3OHME) formation clearance (ClF) show that the extent of Fluosol hemodilution influences both the time and pattern of change in cytochrome P-450 isoenzyme activity. Alterations in antipyrine Vd had no consistent pattern with different extents of hemodilution.

Simultaneous determination of morazone and phenmetrazine in rat plasma and urine using an on-column injection technique with fused-silica capillary column gas chromatography

The simultaneous determination of morazone and its major metabolite, phenmetrazine, using an on-column injection technique with fused-silica capillary column gas chromatography is described. The on-column injection technique prevents the decomposition of morazone. The limit of quantitation in 0.1 mL of rat plasma for morazone and phenmetrazine is 5 ng/mL and that in 1.0 mL of rat urine is 1 ng/mL. The within run precisions (%CV) at the concentration of 0.5 micrograms/mL are 3.27% for morazone and 3.09% for phenmetrazine.