Correlation between dosage and antipyretic effect of aspirin in children

Summary Breast milk and plasma levels of dipyrone metabolites in 8 mothers given a single oral dose of the drug were determined by HPLC. Four metabolites were demonstrated by the analytical method: 4-methylaminoantipyrine (MAA), 4-aminoantipyrine (AA), 4-formylaminoantipyrine (FAA) and 4-acetylaminoantipyrine (AAA). A good correlation was found between the plasma and milk concentrations of the metabolites. The mean (±SD) milk to plasma concentration ratios were: MAA=1.37±0.28, AA=1.15±0.40, FAA=1.03±0.09, AAA=0.97±0.24. The disposition pattern of the dipyrone metabolites in milk was studied in two mothers. None of the metabolites was detectable 48 h after drug administration.     

Plasma kinetics of dipyrone metabolites in rapid and slow acetylators

Summary The pharmacokinetics of the dipyrone metabolites 4-methylaminoantipyrine (MAA), 4-aminoantipyrine (AA), 4-formylaminoantipyrine (FAA) and 4-acetylaminoantipyrine (AAA) were evaluated following the administration of a single oral 1.0 g dose of dipyrone to 23 healthy volunteers. Twelve were slow and 11 were rapid acetylators as previously determined by dapsone phenotyping. For MAA and FAA the mean peak plasma concentrations were 10.5±2.8 µg/ml and 2.1±0.8 µg/ml and the half-lives were 3.3±1.0 and 10.1±1.8 h, respectively. No significant difference was found between rapid and slow acetylators in MAA and FAA kinetics. For AA, the mean peak plasma concentrations were 2.7±0.6 and 1.6±0.7 µg/ml (p<0.01), the peak times 6.7±2.1 and 3.1±1.1 h (p<0.01) and the half-lives were 5.5±1.0 and 3.8±1.2 h in slow and rapid acetylators, respectively. For AAA, the mean peak plasma concentrations were 1.6±0.4 and 4.4±1.1 µg/ml (p<0.01) and the peak time 16.1±5.1 and 10.0±2.6 h (p<0.01) in slow and rapid acetylators, respectively. There was no difference in the elimination half-life between the two groups (10.6±2.2 h). Thus, it has been demonstrated that the AAA/AA ratio is an indicator of the acetylation phenotype, as it is closely correlated with that determined by dapsone (r=0.895, p<0.0005).     

Impairment of the metabolism of dipyrone in asymptomatic carriers of the hepatitis-B virus does not occur in rapid acetylators

OBJECTIVE: We previously found that, compared with healthy subjects. asymptomatic hepatitis-B virus (HBV) carriers displaying slow acetylator phenotype demonstrate a significant prolongation of the elimination half-life of 4-methylaminoantipyrine (MAA) and a decrease in the clearance of formation of 4-aminoantipyrine (AA) and 4-formylaminoantipyrine (FAA). However, the formation of 4-acetylaminoantipyrine (AAA) was unchanged. The present study was designed to examine the effect of the asymptomatic HBV carrier state on the metabolism of dipyrone. as a model drug, in rapid acetylators. METHODS: The plasma and urine concentrations of the metabolites of dipyrone were measured in eight asymptomatic HBV carriers and eight healthy subjects who had normal liver function tests, all displaying the rapid acetylation phenotype and genotype, after the administration of a 1.0-g oral dose of dipyrone. RESULTS: The following pharmacokinetic parameters were evaluated: peak plasma concentration, time to peak plasma concentration, elimination rate constant, area under the plasma concentration-time curve (0-->infinity), amount excreted (0-->infinity), renal and non-renal clearances for MAA and the clearances of formation for AA, FAA and AAA. No significant differences were found between the two subject groups. CONCLUSION: The effect of hepatic viral carrier state on drug metabolism may vary according to metabolic pathways and genetic polymorphism.     

Cerebrospinal fluid and plasma concentrations of dipyrone metabolites after a single oral dose of dipyrone

Objective: Dipyrone is a veteran analgesic and antipyretic drug. After oral administration it is rapidly converted by hydrolysis to 4-methylaminoantipyrine (MAA), which is further metabolized to 4-formylaminoantipyrine (FAA), 4-aminoantipyrine (AA) and 4-acetylaminoantipyrine (AAA). It is still debated whether the site of dipyrone action is in the central nervous system or in the periphery. The purpose of this study was to assess whether dipyrone metabolites cross the blood-brain barrier (BBB) when administered systemically. Methods: Twenty-eight patients undergoing diagnostic lumbar puncture (LP) were randomly assigned to receive two 0.5-g dipyrone tablets either 30 min, 1, 1.5, 2, 4, 6, 8 h or 12 h before the lumbar tap. A 5-ml blood sample was drawn concomitantly. Results: All four metabolites were found in the cerebrospinal fluid (CSF). Their appearance in the CSF lagged but followed that found in the plasma. Mean CSF/plasma ratios were 0.40 (for samples taken between 0.5–2 h) and 0.83 (for samples taken between 4–12 h) for MAA, 0.62 for AA, 0.55 for FAA and 0.40 for AAA (for all samples). Significant correlation was found between plasma and CSF concentrations for MAA, AA, FAA and AAA. Conclusion: The concentration-time course of dipyrone metabolite CSF concentrations are in agreement with that of their plasma concentrations and the analgesic effect of dipyrone. Received: 3 December 1997 / Accepted in revised form: 3 June 1998     

Formation and excretion of dipyrone metabolites in man

Summary The formation and urinary excretion of the dipyrone metabolites, methylaminoantipyrine (MAA), aminoantipyrine (AA), formylaminoantipyrine (FAA) and acetylaminoantipyrine (AAA) were determined following administration of a single oral 1.0 g dose of dipyrone to 12 healthy volunteers. The AAA/AA plasma ratio showed that 3 subjects were slow and 9 were rapid acetylators. Pharmacokinetic parameters were determined separately for each group.A good correlation was found between the plasma and urine AAA/AA ratios. The renal clearance of the four metabolites was similar for both phenotypes. A significant difference in the rate of formation of dipyrone metabolites was found for AA, 0.25 (slow) vs 0.1 ml·min^–1·kg^–1 (rapid), and for AAA 0.75 (slow) vs 7.53 ml·min^–1·kg^–1 (rapid). There were comparable differences between slow and rapid acetylators in the AUC and the urinary excretion extrapolated to infinity for AA and AAA.The present results show that the kinetics of dipyrone metabolites in plasma and urine can provide a useful measure of the activity of the enzymes involved in their production.     

Inhibition of cyclooxygenases by dipyrone

BACKGROUND AND PURPOSE: Dipyrone is a potent analgesic drug that has been demonstrated to inhibit cyclooxygenase (COX). In contrast to classical COX-inhibitors, such as aspirin-like drugs, dipyrone has no anti-inflammatory effect and a low gastrointestinal toxicity, indicating a different mode of action. Here, we aimed to investigate the effects of dipyrone on COX. EXPERIMENTAL APPROACH: The four major metabolites of dipyrone, including the two pharmacologically active metabolites, 4-methyl-amino-antipyrine (MAA) and amino-antipyrine (AA), were used to characterise their binding to COX and haem as well as their effects on the biochemical properties of COX. Mass spectrometry, UV and visible photometry were used to study binding and prostaglandin production. Levels of anti-oxidant enzymes were assessed by Western blotting. KEY RESULTS: The pharmacologically active metabolites of dipyrone, MAA and AA, did not inhibit COX activity in vitro like classical COX inhibitors, but instead redirected the prostaglandin synthesis, ruling out inhibition of COX through binding to its active site. We found that MAA and AA formed stable complexes with haem and reacted with hydrogen peroxide in presence of haem, ferrous ions (Fe(2+)) or COX. Moreover, MAA reduced Fe(3+) to Fe(2+) and accordingly increased lipid peroxidation and the expression of anti-oxidant enzymes in cultured cells and in vivo. CONCLUSIONS AND IMPLICATIONS: Our data suggest that the pharmacologically active metabolites of dipyrone inhibit COX activity by sequestering radicals which initiate the catalytic activity of this enzyme or through the reduction of the oxidative states of the COX protein.     

Stereoselective aspects in the pharmacokinetics and pharmacodynamics of acenocoumarol and its amino and acetamido derivatives in the rat

The stereoselectivity of the pharmacokinetics and of the pharmacodynamics of the oral anticoagulant acenocoumarol (AC) and of two of its potential metabolites, the amino (AM) and the acetamido (AA) derivatives, were investigated in the rat. The pharmacokinetics and pharmacodynamics were investigated following the acute subcutaneous (1 mg/kg) administration of the pure enantiomers. For AC and AA, the S(-)-enantiomer was preferentially eliminated, whereas for AM the R(+)-enantiomer showed the shortest half-life. The differences in elimination between the AC enantiomers were entirely due to differences in total clearance, 183 +/- 14 and 714 +/- 148 ml X h-1 X kg-1 (+/- SD) for R(+)- and S(-)-AC. Also the differences in elimination between the AM enantiomers were mainly due to differences in body clearance, 50 +/- 13 and 18 +/- 4 ml X h-1 X kg-1 for R(+)- and S(-)-AM. For S(-)-AA the higher total clearance as well as the smaller volume of distribution accounted for its 2-fold higher rate of elimination. Acetylation of AM, i.e. the conversion to AA, which accounted for about 50% of its total clearance was stereoselective for R(+)-AM. The renal clearance of AA which accounted for 50-60% of the AA clearance was not selective for one of the AA enantiomers. Stereoselectivity in plasma protein binding was observed, the differences, however, were small. Thus, stereoselectivity in plasma protein binding did not account for the observed differences in the pharmacokinetics. The differences in anticlotting activity between the enantiomers of AC and AM were determined mainly by their pharmacokinetics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Saturable elimination and saturable protein binding account for flavone acetic acid pharmacokinetics

Flavone acetic acid (FAA) is an antineoplastic agent that has undergone extensive study in Phase I trials. Concentration-dependent plasma protein binding has been demonstrated in vitroconcentrations of total drug that are achieved in vivo.Moreover, dose-dependent total systemic clearance has been described when FAA has been administered as a short iv infusion. When administered as a prolonged 24-hr infusion, total FAA (bound plus unbound) plasma pharmacokinetics are well described with a first-order two-compartment model. However, measurement of unbound FAA intra- and post-intravenous infusion in eight patients revealed a twofold increase in fraction of FAA unbound in plasma intrainfusion. We attempted to fit pharmacokinetic structural models of varying complexity to the unbound concentrations alone and simultaneously to the unbound and bound FAA plasma concentrations. The data were adequately described only by a model that incorporated simultaneous saturable plasma protein binding and a Michaelis-Menten process for elimination. A comparison among models is presented, as well as pharmacokinetic parameter estimates for FAA in children. These clinical data are consistent with predictions of the clearance model in which both saturable protein binding (resulting in a dynamically increasing unbound fraction) and saturable elimination (resulting in gradually decreasing unbound intrinsic clearance) are operative.Supported by Cancer Center CORE Grant CA21765, Solid Tumor Program Project Grant NCI 5 PO1 CA 23099, by a Center of Excellence grant from the state of Tennessee, and Amercian Lebanese Syrian Associated Charities.     

Differences in pharmacokinetics and hepatobiliary transport of a novel anti-inflammatory agent between normal and adjuvant arthritis rats

1. The pharmacokinetics, particularly the hepatobiliary transport of T-5557 ((3-methyl-2-oxo-piperadin-3-yl)-acetic acid N '-(3-thieophen-2-yl-8-methoxy-quinazolin-1-yl)-hydrazide), a novel anti-inflammatory agent, has been examined in normal and adjuvant arthritis (AA) rats. 2. Following oral administration of T-5557, the absolute bioavailability in AA rats was increased by sixfold compared with normal rats. The extent of binding T-5557 to plasma proteins obtained from AA rats was markedly greater than in normal rats (97.0 versus 88.2%). The biliary clearance in AA rats was significantly lower than that in normal rats (1.186 versus 5.621 ml?min -1 kg -1), and lower intrinsic biliary clearance was also observed in AA rats (40.33 versus 69.83 ml?min -1 kg -1) . 3. Concomitant administration of T-5557 with quinidine, a potent P-glycoprotein inhibitor, to normal rats caused a significant decrease in the biliary clearance of T-5557 by 37.9%. Moreover, the transport of T-5557 for the apical-to-basal compartment in a Caco-2 cells' monolayer was fourfold lower than that for the opposite direction, and was increased in the presence of quinidine and verapamil. 4. These results suggest that P-glycoprotein is involved in the biliary excretion of T-5557 and the decrease in the transport activity as well as the increase in plasma protein binding caused the elevated plasma concentration and bioavailability of T-5557 in AA rats.     

Serum protein binding of tolterodine and its major metabolites in humans and several animal species

The aim of this study was to determine in vitro protein binding of tolterodine and its 5-hydroxymethyl (5-HM) and N-dealkylated metabolites in serum from humans and several animal species at concentrations similar to those obtained in clinical and preclinical studies. Binding of tolterodine and the two metabolites to human serum albumin and alpha1-acid glycoprotein (AAG) was also assessed, as was binding of tolterodine to red blood cells. Ex vivo protein binding of tolterodine and 5-HM was determined in serum samples from healthy volunteers treated with oral tolterodine 4 mg twice daily for 8 days. Tolterodine exhibited high protein binding in human serum; the unbound fraction (f(u)) was 3.7%. The unbound fraction of tolterodine in cat and dog serum (1.5 and 2.1%, respectively) was lower compared with human serum; f(u) was higher in the other species investigated (rat, 22%; mouse, 16-17%; rabbit, 39%). The unbound fraction of 5-HM was much higher in serum from humans (36%) and all animal species investigated (mouse, 72%; rabbit, 68%; cat, 32%; dog, 45%). Binding of N-dealkylated tolterodine to proteins in human serum was intermediate (f(u) 14%). AAG was the major binding protein for tolterodine and 5-HM, and the degree of binding increased with increasing concentration of the protein. The association constant of 5-HM for AAG was lower than that of tolterodine (1.3 x 10(5) M(-1) versus 2.1 x 10(6) M(-1)). The blood:plasma tolterodine concentration ratio was 0.6 in both humans and dog; thus, a minor fraction of tolterodine was present in red blood cells compared with plasma (0.18 and 0.36, respectively). In the mouse, tolterodine was equally present in blood and plasma. In ex vivo samples, f(u) values for tolterodine (pH adjusted) varied between 1.6 and 4.9% (mean 2.8%), which could be explained by differences in AAG concentrations. There was good correlation between observed f(u) values for tolterodine and those predicted on the basis of AAG levels. Similar findings were observed for 5-HM.     

Differences in pharmacokinetics and hepatobiliary transport of a novel anti-inflammatory agent between normal and adjuvant arthritis rats

1. The pharmacokinetics, particularly the hepatobiliary transport of T-5557 ((3-methyl-2-oxo-piperadin-3-yl)-acetic acid N'-(3-thieophen-2-yl-8-methoxy-quinazolin-1-yl)-hydrazide), a novel anti-inflammatory agent, has been examined in normal and adjuvant arthritis (AA) rats. 2. Following oral administration of T-5557, the absolute bioavailability in AA rats was increased by sixfold compared with normal rats. The extent of binding T-5557 to plasma proteins obtained from AA rats was markedly greater than in normal rats (97.0 versus 88.2%). The biliary clearance in AA rats was significantly lower than that in normal rats (1.186 versus 5.621 ml min(-1) kg(-1)), and lower intrinsic biliary clearance was also observed in AA rats (40.33 versus 69.83 ml min(-1) kg(-1)). 3. Concomitant administration of T-5557 with quinidine, a potent P-glycoprotein inhibitor, to normal rats caused a significant decrease in the biliary clearance of T-5557 by 37.9%. Moreover, the transport of T-5557 for the apical-to-basal compartment in a Caco-2 cells' monolayer was fourfold lower than that for the opposite direction, and was increased in the presence of quinidine and verapamil. 4. These results suggest that P-glycoprotein is involved in the biliary excretion of T-5557 and the decrease in the transport activity as well as the increase in plasma protein binding caused the elevated plasma concentration and bioavailability of T-5557 in AA rats.     

Effects of sodium salicylate on elimination kinetics of indomethacin and bile production in dogs

We investigated the effects of sodium salicylate on the elimination kinetics of indomethacin in bile duct-cannulated beagles. Indomethacin and metabolites were quantified by HPLC in plasma, bile, and urine. Indomethacin was administered as iv bolus injection and iv infusion to yield a steady-state plasma concentration of approximately 1 microgram/ml. Following sodium salicylate, given either iv (25 mg/kg) or via duodenal fistula (50 mg/kg), the indomethacin plasma level dropped instantaneously by 60-70%. Concomitantly, total systemic clearance from the plasma and biliary clearance were increased significantly. In addition, a reduced plasma protein binding of indomethacin and a significant increase in the volume of distribution were observed. The amount of indomethacin, excreted as free and conjugated drug in bile, was significantly increased temporarily by sodium salicylate. The total amount eliminated in bile (approximately 70% of the dose), however, was not changed by sodium salicylate co-administration. The bile flow was significantly enhanced for at least 4 hr. Both phase 1 metabolism and renal excretion of indomethacin remained practically unaffected by sodium salicylate treatment.     

益肺灵对慢性阻塞性肺病及肺心病患者血浆氨基酸的影响

采用高效液相色谱法对健康人、慢性阻塞性肺病 ( COPD)及肺心病患者血浆中的十七种游离氨基酸进行了测定。结果显示 :COPD及肺心病患者血浆游离氨基酸的总量明显高于健康组 ( P<0 .0 0 1)。其中赖氨酸、苯丙氨酸、丙氨酸、酪氨酸、牛磺酸和精氨酸含量明显高于健康组 ( P<0 .0 0 1) ,缬氨酸、谷氨酸含量明显高于健康组 ( P <0 .0 1) ,BCAA/ AAA值明显低于健康组 ( P<0 .0 0 1)。服用益肺灵胶囊治疗后 ,上述指标接近于健康组水平     

黄芩提取物中黄酮类成分血浆蛋白结合率的测定

目的建立同时测定黄芩总黄酮部位中4种黄酮类成分在大鼠血浆中药物浓度的方法,并测定其体外血浆蛋白结合率。方法平衡透析法测定黄芩黄酮类成分血浆蛋白结合率,以高丽槐素为内标,生物样本用甲醇沉淀蛋白进行预处理,采用HPLC法测定4种黄酮类成分在透析内、外液中的浓度。结果在低、中、高3种浓度下,黄芩苷(BL)和汉黄芩苷(WL)的血浆蛋白质结合率随给药浓度的增大而降低(BL:82.03%→77.25%→67.17%;WL:82.24%→76.08%→69.87%),而汉黄芩素(W)和千层纸素A(OA)则呈现非质量浓度依赖性,其平均血浆蛋白结合率分别为(89.66±1.19)%、(88.56±1.87)%。结论该文所建立的测定方法简便、灵敏、专属性强。4个黄酮类成分在大鼠体外均有较高的血浆蛋白结合率。     

超滤法结合液质联用技术测定抗肿瘤化合物CJ-6在不同种属中的血浆蛋白结合率

目的:通过建立测定血浆中抗肿瘤化合物N-(4-((2-(环丙烷甲酰胺)吡啶-4-基)氧基)-3-氟苯基)-4-甲基-3,5-二氧基-2-苯基-2,3,4,5-四氢-1,2,4-三嗪-6-甲酰胺(CJ-6)的分析方法,测定CJ-6在不同种属(大鼠、猴、人)中的血浆蛋白结合率.方法:采取超滤法测定CJ-6在大鼠、猴、人血浆...     

Characteristics of plasma protein binding of tacrine hydrochloride: a new drug for Alzheimer's disease

The aim of this study was to characterise the plasma protein binding of tacrine hydrochloride (THA) in vitro. Binding was assessed in the plasma of 11 healthy individuals aged 20 to 27 years using ultrafiltration followed by HPLC assay.At THA concentrations from 10 to 100 ng/ml protein binding ranged from 78.6 to 71.0%. Binding to commercially available human albumin ranged from 41.7 to 38.3% and to human ₁-acid glycoprotein from 23.1 to 12.4% over the THA concentrations from 25 to 100 ng/ml.THA binding and total plasma protein, plasma albumin and ₁-acid glycoprotein were measured in healthy young subjects (n=13), healthy elderly individuals (n=12) and patients hospitalised with acute illnesses (n=8). There were significant differences between the groups in total plasma protein, plasma albumin and in ₁-acid glycoprotein but no differences in the protein binding of THA which remained constant at about 75%. There was no correlation between THA binding and any plasma protein concentration.The THA binding was not high enough to be of major significance clinically or to reduce the validity of total plasma THA measurement in therapeutic monitoring.     

Plasma protein binding of valproic acid in healthy subjects and in patients with renal disease.

1 Based on the Scatchard plot of the binding data of valproic acid (VPA) it is concluded that the drug is bound by two groups of binding sites with the association constants K1=40.0 X 10(-3) and K2=0.39 X 10(3), and the number of binding sites n1=1.5 and n2=6.8. 2 The binding is dependent on dialysis time, on temperature, on the drug concentration, and on the protein concentration in plasma. 3 At therapeutic plasma concentrations unbound VPA is 8.4 +/- 2.5%, but is increased to 20.3 +/- 4.7% in patients with significant impairment of renal function (P less than 0.001). 4 In patients with renal disease a good correlation is found between unbound VPA and serum creatinine, creatinine clearance, blood nitrogen and uric acid, respectively. A poor correlation is seen between unbound VPA and total protein or albumin concentration in plasma.     

Stereoselectivity and species difference in plasma protein binding of KE-298 and its metabolites.

In vitro protein binding of KE-298 and its plasma metabolites, deacetyl-KE-298 (M-1) and S-methyl-KE-298 (M-2), was high in rat (>97%), dog (>89%) and human plasma (>99%), respectively. Human serum albumin (>93%) was the main protein involved in the binding to plasma proteins, while the binding to human serum globulins was low (16-33%). The binding of KE-298 and its metabolites in all species of plasma was stereoselective. The (+)-(S)-enantiomers of these compounds bound rat, dog and human plasma proteins to a greater extent than did the (-)-(R)-enantiomers, except that the case of KE-298 was opposite in rat plasma. The stereoselective plasma levels of these compounds in rats, dogs, or humans would likely be due to stereoselective differences in binding to plasma albumin. The protein binding of M-1 in adjuvant-induced arthritis rat plasma was >97%, and the stereoselectivity was similar to the case of normal rat plasma. KE-298 and its metabolites remarkably displaced [14C]warfarin, which bound on albumin in a solution of diluted rat serum albumin. Similarly, there was a displacement of [14C]warfarin in solutions of dog and human serum albumin, and concomitantly the displacement of [14C]diazepam. [3H]Digitoxin was not displaced by any of the enantiomers in each albumin solution. No stereoselectivity was found in displacement by enantiomers of the three compounds. These results suggest that stereoselective protein binding can be attributed to quantitative differences in binding to albumin rather than to the different binding sites.     

Effects of ascorbic acid on the metabolic fate and the free radical formation of iproniazid]

The effects of ascorbic acid (AA) on the metabolic fate of iproniazid (IPN) and on the free radical intermediates derived from IPN were investigated in rats. After oral administration of IPN with or without AA, the plasma concentration and the urinary excretion of IPN and its metabolites were determined by gas chromatography-mass spectrometry using stable isotope labeled compounds as internal standards. In the excretion of IPN and its metabolites except hydrazine (Hy), the differences between co-administration and single administration were not observed. The excretion of Hy, which is a known hepatotoxic metabolite, decreased clearly in the co-administration of IPN and AA. When IPN and AA were co-administered orally, the profiles of plasma levels of IPN and its metabolites were almost similar after the administration of IPN alone. Furthermore, no differences between i.v. co-administration and i.v. administration alone were observed. These results indicated that AA did not affect both absorption and metabolism of IPN. By the electron spin resonance (ESR) spectroscopy and spin-trapping technique, the ESR signals due to the alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (4-POBN) adducts induced by isopropylhydrazine (IP-Hy) were two-fold higher than those by IPN in microsomal systems. The free radical formations of IPN and IP-Hy were significantly inhibited by AA in a dose dependent manner. The 4-POBN-trapped radical species generated from IPN and IP-Hy were presumed to be an isopropyl radical by the results of mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS)