THE USE OF ANTIPYRINE IN THE MEASUREMENT OF TOTAL BODY WATER IN MAN

Sex-dependence of body fat distribution in patients with obesity and hypertension

The relationship of body fat distribution with blood pressure, fat cell weight and extracellular fluid volume was studied and compared in 20 obese hypertensive men and 20 obese hypertensive women of similar age, degree of overweight and blood pressure level. Body fat distribution, as reflected by the ratio between waist and hip circumference (W/H ratio), was significantly higher in male than in female obese patients. The W/H ratio was positively and independently correlated with systolic arterial pressure both in males and females. However, for the same W/H ratio, systolic arterial pressure was higher in females. The W/H ratio was positively correlated with gluteal fat cell weight only in males and not in females. Both in males and females, the W/H ratio was positively correlated with extracellular fluid volume, independently of the level of blood pressure level and/or the degree of obesity. The study provided evidence that the relationship between body weight and blood pressure in obese hypertensives is affected by the sex-dependence of body fat distribution with possible interferences on fat cell weight and extracellular fluid volume. Several epidemiological studies have emphasized the positive correlation observed between body weight and blood pressure in many. Many investigations have documented the association of blood pressure with body weight, weight to height, overweight or other indices of fatness such as skinfold thickness. However, the correlation coefficients of these different relationships were found constantly small, indicating that the relationship between overweight and blood pressure is somewhat complex. In patients with hypertension, body weight was shown to be strongly related with the levels of both blood pressure and extracellular fluid volume. On the other hand, patients with overweight and hypertension were found to be principally affected by hypertrophic obesity, as shown by the evaluation of fat cell weight. However these findings were exclusively observed in males. No solid data were reported in females. The relationships between body weight and extracellular fluid on one hand, and between body weight and fat cell weight on the other hand, are certainly different in males and in females. First, in females, extracellular fluid volume is submitted to cyclic changes in sodium balance involving the effect of sex steroid hormones. Second, body fat distribution, a parameter which is weakly correlated to blood pressure, is different in males and females. In males, body fat predominates in the upper part of the body while, in females, adiposity is mainly observed in the lower part of the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioimpedance assessment of antipyrine pharmacokinetics before and after enzyme induction

Bioimpedance (BI) technology, a noninvasive method of measuring body composition, has been previously used to develop a predictive model for metabolic clearance under basal conditions. The present investigation was conducted to assess the ability of BI-derived models to predict drug disposition in a perturbed system. An antipyrine pharmacokinetic and impedance analysis of 15 healthy male subjects was performed before and on the 14th day of phenobarbital administration (i.e., after enzyme induction). The all subsets multiple regression technique was used to develop preinduction models for clearance (CI), (p = 0.021, R2 = 0.654) and volume of distribution at steady-state (Vdss) (p = 0.001, R2 = 0.867), using demographic and mean BI parameters. The preinduction Cl model significantly underestimated postinduction measurements and was not predictive of changes in Cl. The preinduction Vdss model was predictive of postinduction Vdss. It appears that the BI-derived model is unable to predict perturbations in metabolic clearance caused by enzyme induction.

Assessment of liver ability to biotransformation of antipyrine in uraemic patients on regular peritoneal dialysis treatment

It was the aim of this work to establish whether biotransformation of drugs by the liver expressed by antipyrine kinetics is disturbed in peritoneally dialysed patients with end-stage renal failure. The investigations were carried out in 10 uraemic patients using the antipyrine test and comparing the parameters of antipyrine kinetics with those obtained in 13 healthy persons. Our results indicate that in uraemic patients on regular peritoneal dialysis treatment antipyrine kinetics are generally in the normal range, suggesting the microsomal content of cytochrome P-450 being not evidently reduced.

Dual-isotope measurement of lung water

Iodine-131-labeled iodo-antipyrine and 99mTc-labeled erythrocytes were used to measure water content in lungs. These radioactive tracers were injected into 11 dogs with injured lungs. Blood samples were drawn and the animals sacrificed. The lungs were removed, weighed and homogenized. Samples of blood and lung homogenate were assayed for 131I and 99mTc. Samples were also weighed before and after drying to a constant weight at 70-76 degrees C. Extravascular lung water was determined by the dual-isotope technique and again by gravimetric analysis. The average ratio of the results from the two different methods was 1.14 +/- 0.20. The two methods were also compared by regression analysis and the correlation coefficient was 0.97 +/- 0.09.

Twitch potentiation of frog (Rana japonica) skeletal muscle by antipyrine

1. The effects of antipyrine on single muscle fibres from the frog Rana japonica were examined. Antipyrine potentiated the twitch tension, but did not affect the tetanus response or induce any contracture by itself. 2. The duration of the action potential was prolonged in a dose-dependent manner. 3. Antipyrine did not affect the mechanical threshold, the uptake of Ca2+, or the Ca2+ induced release of Ca2+ from the sarcoplasmic reticulum. 4. Ca2+-channel blockers did not affect the twitch potentiation by antipyrine.

Lung water measurements with iodo-antipyrine

131I labeled iodo-antipyrine and 99mTc labeled erythrocytes were used to measure water content in lungs. These radioactive tracers were injected into 10 rabbits with normal lungs and 11 rabbits with injured lungs. Blood samples were drawn and the subjects were killed. The lungs were removed, weighed and homogenized. Samples of blood and lung homogenate were assayed for 131I and 99mTc. Samples were also weighed before and after drying to a constant weight at 70-75 degrees C. Extravascular lung water was determined by the dual isotope technique and again by gravimetric analysis. The average ratio of the results from the 2 different methods is 1.03 +/- 0.15. The 2 methods were compared by regression analysis and the correlation coefficient was 0.92 +/- 0.09. Our investigation suggests the possibility of measurement of lung water with equilibrium distribution of iodo-antipyrine.

Measurement of D2O concentrations at tracer levels in small samples obtained from paediatric patients

A micro-method is described for the determination of trace amounts of D2O in serum, saliva and urine, requiring 100 microliters of sample. H2O/D2O are rapidly isolated from serum, saliva or urine by vacuum distillation. D2O concentrations in H2O are detected by infrared spectroscopy utilizing the integrated absorption of the OD-bond at 2510 cm-1 in the range of 2675 to 2460 cm-1. Calibration is done using standard solutions of H2O/D2O. The separation of D2O/H2O is necessary because of the varying background absorption of the sample. The recovery of D2O after distillation is 100%. The absolute error is 25 mg/kg (+/- 2 s) of D2O leading to a precision of 17.5% at 150, 2.8% at 1000, 1.3% at 2000, 0.9% at 3000, 0.7% at 4000 and 0.5% at 5000 mg/kg of D2O. The usefulness of the method is evaluated by 9 determinations of total body water and water turnover in 7 healthy subjects drinking a mixture of H2O/D2O. Total body water related to body surface is 23.3 +/- 0.9 l/m2 in males and 20.5 +/- 1.5 l/m2 in females. Water turnover is determined by analysing the decrease of D2O concentrations in blood between 6 and 31 days. A mean of 1.53 +/- 0.13 l/m2.d in males in 1.48 +/- 0.17 l/m2.d in females was found.

Dynamics of deuterium turnover in the human body using 2(1)D(gamma, n) reaction

A rapid non-destructive and sensitive technique is used by which total body water and its rate of turnover (excretion) in human subjects can be easily measured. Subsequently, a simple calculation is made in estimating the total body fat and lean body mass. The measurements are, therefore, expected to shed useful light on the measurement technique as well as on the movement of body water in humans, and this will glean an understanding of physiological laws governing such movements. The method employs the activation of deuterium in water by bremsstrahlung radiations which are produced by stopping 3 MeV electrons in a gold target. The detection of photoneutrons, so obtained in the reaction 2(1)D(gamma, n), is accomplished by the capture of fission fragments in Solid State Nuclear Track Detector (SSNTD) issuing from the 235U(n, f) reaction. These fission events are then automatically counted by a spark counter. Thermal neutrons, required for the 235U fissioning, are obtained by employing a graphite moderator assembly at the core of which water and urine samples are being irradiated. The development of a few basic measurement parameters and their utilization in such measurements are also reported in the paper.

Antipyrine clearance and metabolite formation: the influence of liver volume and smoking

The influence of liver volume and cigarette smoking on antipyrine clearance and metabolite formation was studied in seventeen volunteers (eight smokers, nine non-smokers). Inter-test coefficient of variation of liver volume (as determined by ultrasound) was 6.3%. The mean antipyrine clearance was 49.3 +/- 18.3 ml min-1 and when normalized for liver volume 36.1 +/- 10.1 ml min-1 l-1. The antipyrine clearance per unit volume of liver was significantly higher in smokers (43.0 +/- 10.5 ml min-1 l-1), than in non-smokers (30.0 +/- 4.6 ml min-1 l-1) (P less than 0.01). No significant difference was found between the two groups as to the excreted amounts of 4-hydroxyantipyrine (OHA), norantipyrine (NORA), and 3-hydroxymethylantipyrine (HMA). Normalized for liver volume the mean clearances for production (Clm) of these metabolites were significantly higher in the group of smokers than in the group of non-smokers. The greatest change was observed for OHA formation. However, analysis of variance showed that the differences in the percentages of change of the mean Clm of these metabolites in the two groups are not significant.

Extracellular and interstitial fluid volume in obesity with and without associated systemic hypertension

Fluid volumes and cardiac and renal hemodynamics were investigated in 44 obese men, 22 with normal blood pressure and 22 with sustained essential hypertension. For the same degree of obesity hypertensive patients had a higher value in extracellular (p less than 0.05) and interstitial fluid (p less than 0.01) volumes than normotensive subjects, while plasma volume, total body water, body cellular water, cardiac output, renal blood flow and glomerular filtration rate were similar. For the same level of blood pressure, the expansion of extracellular and interstitial fluid volume paralleled the degree of obesity. Thus, obese patients with hypertension have an absolute increase in extracellular and interstitial fluid volumes. The increase was related both to the degree of overweight and to the mechanisms of hypertension.

Measurement of body fat and hydration of the fat-free body in health and disease

Body fat mass, fat-free body mass and body water are basic components of body composition which are used in nutritional and metabolic studies and in patient care. A method of measuring total body fat (TBF), fat-free mass (FFM) and its hydration (TBW/FFM) involving prompt gamma in vivo neutron activation analysis (IVNAA) and tritium dilution has been compared with the more traditional methods of densitometry and skinfold anthropometry in 36 normal volunteers, and with skinfold anthropometry in 56 patients presenting for nutritional support. While the mean values of TBF were in reasonable agreement for the three methods in normals it was founds that skinfold anthropometry underestimated TBF relative to the IVNAA/tritium method by, on average, 3.0 kg (19%) in patients. Furthermore, the ranges of values in normals of the ratio TBW/FFM for the anthropometric (0.62 to 0.80) and densitometric (0.65 to 0.80) methods were much wider than the range for the IVNAA/tritium method (0.69 to 0.76), in which TBW was measured by tritium dilution in all cases. In the patients, the ranges of this ratio were 0.52 to 0.90 for the anthropometric method and 0.67 to 0.82 for the IVNAA/tritium method; clearly anthropometry yields values of TBW/FFM which are outside accepted biological limits. On the basis of these findings, ranges of TBW/FFM are suggested for both normal adults (0.69 to 0.75) and patients requiring nutritional support (0.67 to 0.83). Finally it is concluded that the IVNAA/tritium method is a suitable method for measuring TBF and FFM and particularly so when body composition is abnormal.

Influence of short-term water deprivation on antipyrine disposition

The effects of acute (96 h) water deprivation on the disposition kinetics of antipyrine and hepatic cytochrome P-450 content were investigated in male rats. The disposition kinetics of antipyrine in rats deprived of water for 96 h was altered significantly: the total body clearance and steady-state volume of distribution decreased by 27.1 and 22.4%, respectively, as compared to control rats. There was no significant change in the disposition rate constant as a result of simultaneous changes in the volume of distribution and clearance. There was a 51.4% decrease in the hepatic cytochrome P-450 content in water-deprived rats. These results suggest that the pharmacokinetic changes observed in acute water deprivation with a model drug, antipyrine, are related to a decrease in total body water and to a reduced amount and/or activity of the hepatic microsomal oxidative enzymes.

Human pharmacokinetics of analgesics and methods for their determination in biological fluids

The main pharmacokinetic data of analgesics--biological half-lives, apparent volumes of distribution, total body clearances--obtained in humans, and their clinical relevance are summarized. Special emphasis has been given to the analytical methods used for the quantitative determination of these drugs in biological fluids.

The effect of exercise on the total water space and red blood cell volume of the gracilis muscle of the dog

The effect of increasing intensities of exercise on the water space and the red blood cell volume of the dog gracilis muscle was determined with 125I-labelled iodoantipyrine (n = 8) and 99mTc labelled red blood cells (n = 4). A sodium iodide scintillation probe attached to a two channel multiscaler and printer recorded the 125I activity of the muscle as a measure of the water space and the 99mTc activity as a measure of the red cell space. An electro-magnetic flow probe recorded muscle blood flow: aortic pressure was measured with a catheter in the mid-abdominal aorta. At least 30 min after i.v. administration of iodoantipyrine and red blood cells, the obturator nerve was electrically stimulated to produce muscle contraction at 1 contraction per second for 5 min. Data were recorded prior to exercise, during the 5 min exercise period, and for 10 min after exercise. During the greatest exercise period there was an eightfold increase in muscle blood flow, but only a small increase in [125I]iodoantipyrine activity (2.7 +/- 0.8%, 95% confidence limits) and 99mTc red blood cell activity (3.2 +/- 2.1%). Both values promptly returned to baseline during recovery. These data show that there is a minimal change in the water space and blood volume of the exercising dog gracilis muscle.

Effects of glucose on alanine-derived urea synthesis

The effect of glucose on alanine-stimulated urea synthesis was studied in six healthy volunteers during 6 h of constant alanine infusion, 2.8 mmol h-1 kg-1 b. wht., and during 12 h of constant glucose infusion, 4.0 mmol h-1 kg-1 b. wht., with superimposed alanine infusion. The urea nitrogen synthesis rate (UNSR) was determined at intervals of 2 h as urinary excretion rate corrected for accumulation and intestinal hydrolysis. UNSR depended on the blood alanine and glucagon concentration, but was not correlated with glucose, lactate, or insulin concentrations. The slope of the linear relation between UNSR and alanine concentration (the 'Functional Hepatic Nitrogen Clearance') was on the average 24.4 1 h-1 and decreased to 12.8 1 h-1 by glucose (mean difference +/- SE of the difference 10.6 +/- 7.3, P less than 0.01). The relation between glucagon and alanine concentration was linear, and the slope was decreased to 40 per cent by glucose (P less than 0.05). The slope of the linear relation between UNSR and glucagon was not changed by glucose. Thus the catabolism of alanine nitrogen is decreased by glucose because of a reduction of the urea synthesis. Data suggest that this may be due to a depression of the glucagon response to alanine.

Noninvasive assessment in vivo of hepatic drug metabolism in health and disease

Despite the availability of techniques and concepts for examining the physiologic processes of drug disposition and clearance by the liver in normal subjects and in patients with liver disease, important questions remain in this field. Major problems include high inducibility of hepatic drug-metabolizing enzymes, even in patients with liver disease (normal drug clearances can occur in liver disease patients who chronically ingest drugs that induce these enzymes); poor correlation between routine liver function tests, such as SGOT, SGPT, alkaline phosphatase, and bilirubin, and alterations of hepatic drug metabolism in hepatocellular disease; failure of all drugs to be similarly affected in liver disease, even for drugs with similar metabolic pathways. Nevertheless, certain test drugs, such as antipyrine and aminopyrine, whose clearances from plasma or saliva closely reflect their hepatic metabolism, may serve as probes to explore under normal and disease conditions how drugs are handled in the liver. Nevertheless, limitations in the use of antipyrine and aminopyrine metabolism as tests of hepatic function must be recognized: special conditions of patients may render results of these tests by themselves impossible to interpret. Utilizing additional drug substrates and measuring rates of formation of individual metabolites, as well as disappearance of parent drug, investigators may be able to research more effectively and in greater detail for interrelationships between liver disease and the processes of hepatic drug metabolism, hepatic blood flow, and even other, as yet unidentified, processes that influence liver and drugs interactions.

Effect of posture on ampicillin pharmacokinetics, glomerular filtration rate and renal plasma flow in resting subjects

Differences in drug kinetics between supine rest and ambulation have been reported, but the relative contribution of postural changes and changes in the level of physical activity has not been evaluated. Ampicillin pharmacokinetics, glomerular filtration rate (GFR) and renal plasma flow (RPF) were studied in six male volunteers at rest in the sitting and lying position with an interval of 1 week. After intravenous administration ampicillin kinetics, analyzed according to a two-compartment open model, demonstrated significant changes in drug distribution when the position was changed from lying to sitting: alpha-increased by 50%, V1 and V beta increased by 19% and 22% respectively. Ampicillin clearance, the fraction of dose recovered from urine, GFR and RPF were, however, not influenced by the change in posture. Our data on effects of posture in resting subjects suggest that previously reported differences in drug elimination and RPF between lying and ambulatory subjects are largely due to differences in the level of physical activity.

Intravascular volume, extracellular fluid volume, and total body water in obese and nonobese hypertensive patients

Intraarterial blood pressure, plasma volume, extracellular and interstitial (IFV) fluid volumes, and total and intracellular (IBV) body water were evaluated in 50 men: 16 obese hypertensive patients, 16 nonobese hypertensive patients, and 18 normal subjects of similar age. In obese hypertensive subjects, the IBW/IFV ratio was significantly increased (p less than 0.01) in comparison with both control subjects and nonobese hypertensive patients. After body weight reduction, blood pressure (p less than 0.01), heart rate (p less than 0.05), and the IBW/IFV ratio (p less than 0.01) significantly decreased. The decrease in the ratio was due to an absolute increase in the interstitial fluid volume, related to a shift of fluid volume from the intracellular to the interstitial space. Thus, obese hypertensive patients have an increased water cell content, causing an altered partition between the intracellular and the interstitial spaces.

Studies on regional blood flow of the mouse using whole-body autoradiography of 14C-iodoantipyrine

In order to visualize regional blood flow in various tissues of the mouse at the same time, the distribution of radioactive carbon from 14C-iodoantipyrine was studied by whole-body autoradiography. The mice were frozen with Dry-Ice-hexane at 1, 10, 30 min, and 1 h and 3 h after intravenous injection of 14C-iodoantipyrine. Whole-sagittal sections of the frozen mouse, obtained by using a cryostat microtome, were dried in a cryostat and subjected to autoradiograhy. The resulting dry autoradiographs are called untreated autoradiographs in the present work. The sections were then fixed in cold 6% (w/v) HClO4, dried at room temperature and again subjected to autoradiography. Autoradiographs thus obtained are referred to as treated autoradiographs. It was found that the method could be suitable for the estimation of regional blood flow of the renal cortex, spleen, lung, skeletal muscle, bone marrow, thymus, testes, and brain.

A non-invasive method for the study of hepatic drug metabolism in rodents: antineoplastic drug effects on antipyrine metabolism in mice

A rapid, sensitive and simple high pressure liquid chromatography (HPLC) method is described for the direct analysis of antipyrine in saliva. The detection limit was found to be 1.0 ng/ml of sample, lower than any previously reported method. Accuracy and precision were maintained with as little as 0.5 microliter of saliva. Thus the rate of elimination of antipyrine has been monitored non-invasively in rats and for the first time in mice. The antipyrine half-life was found to be 28.9 +/- 4.0 (S.E.M.) min and 111 +/- 20 min in mice and rats, respectively. In mice single i.p. doses of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) (30 mg/kg) produced increases in antipyrine half-life, up to 28 days post-treatment. The maximum effect of BCNU was observed on day 7 with an antipyrine half-life of 74.4 +/- 15.7 min. Phenobarbital induction lowered the antipyrine half-life in controls to 12.6 +/- 1.2 min. An enhanced inductive effect was observed in BCNU-treated mice: BCNU-treated, phenobarbital-induced mice displayed a half-life for antipyrine of 7.4 +/- 0.6 min on day 21 post BCNU dose. These effects could not be attributed to changes in absorption of antipyrine in BCNU-treated mice.

Elimination of pindolol in liver disease

The elimination of pindolol was studied in 32 patients suffering from various liver diseases, mainly acute hepatitis and hepatic cirrhosis. The total body clearance of antipyrine was measured simultaneously as a parameter of liver microsomal enzyme activity. The doses given were antipyrine 1000 mg orally and pindolol 3 mg i.v. Plasma samples were taken and urine was collected for up to 72 h for the measurement of drug concentrations. In addition, conventional biochemical laboratory tests were done. The total body clearance of antipyrine was compared with the pharmacokinetic parameters calculated for pindolol, and the results of the biochemical tests. No correlation was found between antipyrine clearance and the routine biochemical parameters in liver disease or with the total body clearance of pindolol. A significant correlation was seen with the nonrenal clearance of pindolol taken as representing its major metabolic degradation. Higher correlation coefficients were observed when two subgroups of patients with acute hepatitis and hepatic cirrhosis were separated. In some patients suffering from hepatic cirrhosis a higher urinary excretion of unchanged pindolol was observed as liver function become decompensated, a finding due to an unknown mechanism but based on intact renal function. In patients with acute hepatitis a much higher nonrenal clearance was found than in many other patients, which might be based on increased liver blood flow.

Cholestasis and hepatic drug metabolism. Comparison of metabolic clearance rate of antipyrine in patients with intrahepatic or extrahepatic cholestasis

The antipyrine metabolic clearance rate (MCR) was studied in two groups of patients with similar degrees of cholestasis and hepatic damage, but differing mechanisms of cholestasis. The plasma disappearance rate of antipyrine in 18 patients with extrahepatic cholestasis and 11 patients with intrahepatic cholestasis was compared with that of two groups of control subjects without liver disease who were matched for age. Whereas no significant difference was observed for the antipyrine MCR between patients with extrahepatic cholestasis and their controls [30.7 +/- 11.2 (SD) as against 31.6 +/- 10.0 ml/min], the antipyrine MCR was significantly lower (P less than 0.001) in the patients with intrahepatic cholestasis than in their controls (16.2 +/- 4.5 vs 37.4 +/- 17.3 ml/min). These results suggest that cholestasis per se does not change the rate of metabolism of drugs by the liver. The decrease of antipyrine MCR in patients with intrahepatic cholestasis could be due to a reduced functional parenchymal mass related to some degree of hepatic necrosis.

Metabolic ability and enflurane defluorination in surgical patients

Antipyrine clearance and half-life, which are measures of the hepatic metabolic ability, were determined prior to anaesthesia in 14 surgical patients. The antipyrine results correlated neither with the highest serum fluoride concentrations nor with the fluoride excretion in urine following administration of enflurane. Enzyme induction may therefore have little influence on enflurane metabolism in man. Inorganic fluoride concentrations in serum and in excreted urine were determined following the exposure of a total of 21 surgical patients to measured doses of enflurane. In the group of 14 patients tested for metabolic ability, a mean dose of 0.4 end-tidal vol. % X h enflurane resulted in a mean peak serum fluoride concentration of 6.8 mumol/l (maximum 13.6 mumol/l) 2 h after enflurane exposure. In the material as a whole, the enflurane dose was positively correlated with both post-anaesthetic highest serum fluoride concentrations and the 24-h post-anaesthetic urine pH (P less than 0.01) as well as urinary volume and fluoride excretion in urine during that time. At a urinary pH below 5.0, the fluoride excretion was very low, while the highest excretions were associated with a urinary pH of about 7.0. Raising the patient's per- and post-anaesthetic urine pH and maintaining a good urinary output (which also tends to increase urine pH) may be enough to prevent accumulation of inorganic fluoride in the body following enflurane anaesthesia.

Comparative pharmacokinetics of antipyrine (phenazone) in the baboon, cynomolgus monkey and rhesus monkey

The pharmacokinetics of antipyrine (phenazone) in 3 species of non-human primate have been evaluated following its intravenous administration at a dose level of 92 mg/kg. Mean peak plasma concentrations of antipyrine of 132, 137 and 155 microgram/ml in the rhesus monkey, the cynomolgus monkey and the baboon respectively were not observed until 5 min after intravenous injection. Thereafter, concentrations declined with an apparent half-life of elimination of 1.5-2 h. The time-course of plasma antipyrine concentrations was adequately described by a one-compartment open model and no notable differences in pharmacokinetic parameters utilising a 2-compartment open model were observed. Antipyrine was mainly distributed in total body water. The mean volume of distribution was equivalent to 88, 73 and 66% of body weight in rhesus monkey, the cynomolgus monkey and the baboon, respectively. An analysis of variance of volumes of distribution, apparent half-lives of elimination and systemic clearances showed that there was a statistically significant species-related difference in systemic clearance (P less than 0.05) and volumes of distribution (P less than 0.01) which were lower in the cynomolgus monkey than in the other 2 species. The pharmacokinetics of antipyrine in the non-human primate are more similar to those of other laboratory animal species than to those of humans.

Synthesis of urea after stimulation with amino acids: relation to liver function

Hepatic urea synthesis is the organism's main channel for the disposal of nitrogen and it may be an 'essential' liver function. In six control subjects and five patients with cirrhosis of the liver urea synthesis was studied during continuous infusion for six to 24 hours of about 3 mmol alpha-amino nitrogen/h X kg body weight. The urea synthesis rate was calculated in intervals of two hours as urinary excretion with correction for accumulation in the total body water and for hydrolysis of urea in the gut. The peripheral venous plasma alpha-amino nitrogen concentration increased from 3 to about 14 mmol/l and the urea nitrogen synthesis rate from 25 to about 215 mmol/h. In all cases the urea synthesis rate rose linearly with the alpha-amino concentration throughout the examined range. The slope of this linear relationship is an expression of the hepatic conversion of alpha-amino nitrogen to urea nitrogen ('functional hepatic nitrogen clearance'). The functional hepatic nitrogen clearance was 22.4 l/h in control subjects and 13.7 1/h (P < 0.025) in the patients with cirrhosis. It was correlated with quantitative measures of the liver function (the galactose elimination capacity, r = 0.84, and the clearance of antipyrine, 4 = 0.80). These observations, while confirming the abundant capacity of the urea synthesis system, imply that a given urea synthesis rate requires a higher alpha-amino level in patients with reduced liver function.

Infrared-spectrometric determination of D2O in biological fluids. Reappraisal of the method and application to the measurement of total body water and daily water turnover in the dog

The determination of D2) in biological fluids by means of infrared spectrometry was reinvestigated. When the temperature of a solution, containing D2O in the range from natural abundance to 5 ml . 1-1 increases, its absorbance decreases and the wavenumber of maximum absorption shifts to a higher value. Both changes are linearly related to the change in temperature. Storage for 17 d in either glass or polyethylene tubes does not affect the D2O concentration. Purification of biological fluids by vacuum-sublimation removes all substances which also absorb at the O-D vibration band and the recovery of D2O from plasma and urine is complete. The partition ratio of D2O between plasma water and red cell water equals unity, and the same holds for plasma water and urine water over a wide range of urine flows and osmolalities. The arterial and urinary disappearance curves of D2O, measured over several days, both permit the calculation of the total amount of body water (Vbw), the daily water turn-over (F) and the half-time of water in the body (t1

Microsomal enzymes in patients with acute leukemia as determined by plasma half-life of antipyrine

The metabolism of antipyrine was studied in five patients with acute leukemia, before and after treatment and in relapse, to ascertain the effects of treatment on hepatic microsomal enzyme activity. The mean antipyrine half-life was significantly longer in patients after treatment (15.0 +/- 3.7 h) than in patients before treatment (8.8 +/- 0.7 h) (P less than 0.02). Furthermore, the mean antipyrine half-life in patients after treatment was also significantly longer than in patients in relapse (9.2 +/- 2.7 h) (P less than 0.05). Similarly, the mean metabolic clearance rate of antipyrine was significantly lower in patients after treatment (26.9 +/- 2.2 ml/h/kg) than in patients before treatment (46.7 +/- 13.1 ml/h/kg) (P less than 0.02). The mean apparent volume of distribution was not significantly different during the course of acute leukemia. The mean transaminase activity in patients after treatment was significantly higher than that in patients before treatment and in relapse. Thus, treatment with antileukemic agents and blood transfusions might alter hepatic microsomal enzyme activity.

Partition of 125I-iodoantipyrine among erythrocytes, plasma, and renal cortex in the dog

The tissue/blood partition coefficient, lambda tb, defined as the amount of blood having the same tracer content as one unit of tissue at diffusion equilibrium, was determined for 125I-iodoantipyrine (I-Ap) and tritiated water (THO) in the dog kidney cortex. Measurements were made after in vivo equilibration for 75 to 300 s and with liver circulation excluded. In 18 kidneys, lambda tb for I-Ap averaged 1.38 (S.D. 0.13) w/w (weight/weight), without significant correlation to hematocrit (range: 23-43) or to urine pH (range 5.5-8.6). The lambda tb for THO averaged 0.97 (S.D. 0.06) v/w (volume/weight), close to the relative water contents. Erythrocyte/plasma partition for I-Ap was 0.82 w/w, compared to a water partition of 0.72. Thus, at diffusion equilibrium the apparent I-Ap concentration in renal cortical and red cell water exceeds that of plasma water by 14 and 60%, respectively. It follows that I-Ap cannot be used as a general indicator for total tissue water content. When used for measurement of local blood flow and modum Kety, lambda tb must be determined for each tissue and species.

High-pressure liquid chromatographic analysis of antipyrine in small plasma samples

A high-pressure liquid chromatographic (HPLC) method was developed for the assay of antipyrine in small (0.1-ml) plasma samples using aminopyrine as the internal standard and a reversed-phase microparticulate column. The assay sensitivity (1 microgram/ml) permits development of a plasma level--time curve using a single rat. The mean (+/- SE) plasma elmination half-life in rats was 1.28 +/- 0.14 hr. A comparison of the spectrophotometric method with the HPLC method yielded a correlation coefficient of 0.98. The HPLC assay for antipyrine is rapid and precise and can be used for hepatic drug metabolism study in a single animal.

Antipyrine elimination in critically ill patients

Antipyrine kinetics were studied in 12 critically ill patients. Antipyrine half life was found to be short (6.5 +/- 3.4 h), this did not alter over 4 days of acute illness, although there was a tendency for antipyrine clearance to decrease over that time period. The need for further pharmacological studies in critically ill patients is stressed.

Effect of surgery under general anaesthesia on antipyrine clearance

1 The effect of surgery under general anaesthesia on drug metabolism was investigated in man. The activity of hepatic drug-metabolizing enzymes was evaluated by measurement of antipyrine clearance, before surgery and 3 days after surgery, in eighteen patients. 2 In those patients in whom the operation lasted 2 h or less, the postoperative clearance of antipyrine was significantly (P less than 0.05) increased by 48%; in those patients in whom the operation lasted 2--4 h, it was non-significantly decreased by 36%; in those patients in whom the operation lasted more than 4 h, it was significantly decreased by 47% (P less than 0.01). 3 It is concluded (a) that short operations are followed by increased activity of hepatic drug-metabolizing enzymes, whereas (b) protracted operations are followed by decreased activity. It is suggested (a) that the former effect may be a consequence of enzyme induction by drugs used for premedication and anaesthesia, whereas (b) the latter effect may be the result of major surgical trauma.

Suction blister fluid as a model for interstitial fluid in rats

1. Suction blisters on the skin of rats, obtained with a negative pressure of 150 mm Hg, show a close similarity to human suction blisters, based on histological, electrolyte and protein findings. 2. Pharmacokinetic experiments with inulin and antipyrine have proved that the movement of these low protein binding drugs between blister fluid and serum follows the laws of diffusion. 3. The investigations suggest that blister fluid resembles interstitial fluid and can therefore serve as a model for the estimation of drug concentrations in interstitial fluid.

Apparent volumes of distribution and drug binding to plasma proteins and tissues

A pharmacokinetic model that incorporates linear binding of drug to plasma proteins and tissue indicates the same relationship between apparent volume of distribution and drug binding as that proposed by Gillette (1971) based on a simple distribution model. Apparent volume of distribution (V) is directly proportional to free fraction of drug in plasma (fp) and indirectly proportional to free fraction of drug in tissue (fT). In the case of a constant fT, a plot of V versus fp will be linear with an intercept equal to plasma volume (Vp). If fT changes with fp, an apparently linear plot may result but the intercept will exceed Vp. An approach to the calculation of fT, a composite binding parameter, is presented and illustrated by comparing the tissue binding of tolbutamide in patients during acute viral hepatitis and upon recovery.

Liver size and indices of drug metabolism in alcoholics

The role of liver size in drug metabolism was investigated in 34 chronic alcoholics and 28 controls by comparing antipyrine half-life with biopsy content and total amount of hepatic cytochrome P-450 (P-450) and liver weight. Liver size was significantly greater in alcoholics than in controls. Total P-450 was increased and antipyrine metabolism was enhanced in alcoholics with normal histology of the liver. In subjects with alcoholic hepatitis or cirrhosis, the antipyrine half-life was prolonged and P-450 was decreased. Alcoholics with fatty liver had a reduced P-450 content, but the total amount of P-450 and the antipyrine half-life were normal. The results demonstrate in alcoholics that an enlarged liver of normal histological appearance is associated with enhanced drug metabolism. In subjects with fatty liver the drug metabolizing capacity per unit weight of liver is often impaired, but the increase in liver size leads to undisturbed total oxidizing capacity and normal in vivo metabolism. In alcoholic hepatitis drug metabolism is impaired in spite of hepatomegaly. In cirrhosis the enlargement of the liver appears to compensate for the decreased P-450 content resulting in only slightly decreased total P-450, and the severly impaired in vivo drug metabolism may be due to derangement of blood flow.

Salivary antipyrine kinetics in hepatic and renal disease and in patients on anticonvulsant therapy

The effects in man of liver disease, renal failure and hepatic microsomal enzyme induction on the elimination kinetics of antipyrine in saliva have been examined. Antipyrine (10 mg/kg) was given orally and assayed in saliva by gas-liquid chromatography. The mean antipyrine half-life from saliva in nine epileptic subjects receiving long term anticonvulsant drug therapy (6 hr +/- 0-9 SEM) was significantly shorter than in twenty normal healthy volunteers (10-7 +/- 0-6). Therapy included phenytoin and phenobarbitone, two drugs known to induce hepatic microsomal enzymes. Five subjects with chronic renal failure exhibited no significant difference in salivary anti-pyrine half-life (11-7 +/- 1-9) compared to the control group, whereas six subjects with chronic liver disease and impaired hepatic function had significantly increased half-life values (42-4 +/- 10). The results suggest that differences in the activity of hepatic microsomal enzymes are reflected by changes in salivary antipyrine elimination kinetics. Chronic renal failure appeared to have no effect on the function of these enzymes.

Partition of xenon and iodoantipyrine among erythrocytes, plasma, and myocardium

A new method was developed for determining directly the distribution of 133Xe between red cells and plasma in vitro without an air-fluid interface; the partitioning of 133Xe and 133-i-iodantipyrine between blood and myocardium was investigated in the dog in situ. The red cell-plasma partition coefficient for 133Xe (lambdacpX, unit: ml/ml) at 37 degrees C was 2.27 +/- 0.07 (mean +/- SD) for human blood and 3.31 +/- 0.06 for dog blood. The red cell-plasma partition coefficient for 131I-iodantipyrine (lambdacpI, ml/ml) was 0.75 +/- 0.04 for human blood and 0.97 +/- 0.03 for dog blood. lambdacpX and lambdacpI did not change significantly after the intravenous administration of sodium pentobarbital (30 mg/kg) into the dog. lambdacpX of dog blood varied inversely with temperature, whereas lambdacpI showed very little change with temperature. The blood-left ventricle partition coefficient for 133Xe (lambda'btX, corrected for trapped blood) varied directly with directly with red cell volume fraction (H): lambda'btX = 1.32 + 2.00 H. Blood-left ventricle partition coefficient for 131I-iodoanitpyrine did not vary significantly with H. The results support the concept of a three-compartment partition of the indicator among erythrocytes, plasma, and myocardium. The mean values (+/- SD) of the hematocrit-independent plasma-tissue partition coefficient in the left ventricle for 133Xe and 131I-iodoantipyrine were 1.08 +/- 0.16 and 1.54 +/- 0.20 g/ml, respectively.

Precise measurement of total body water using trace quantities of deuterium oxide

This study was undertaken to investigate the possibility of measuring total body water in human subjects to better than +/-0.5%. Accurate serial estimates of total body water were required to complement densitometric and anthropometric measurements used to monitor body compositional changes in obese patients undergoing dietary or surgical weight reduction therapy. The method required the oral administration of 1-2 g of deuterium oxide and the analysis of pre-dose and respective equilibrated samples of urine, plasma or saliva. The sample size required for analysis was 5 microliter and the conversion of gaseous phase was accomplished using a uranium reduction furnace. Isotopic enrichment of samples was measured using a mass spectrometer incorporating several features designed to cope with problems inherent in H2/H2H isotopic analysis. Reproducibility of sample preparation and accuracy of the mass spectrometer were tested using international standards and shown to give an overall sensitivity of 2 parts in 10(7) for the determination of deuterium in H2O/H2HO mixtures. This precision has enabled us to demonstrate that isotopic fractionation of deuterium with respect to hydrogen occurs within the body and expands the potential use of this isotope for quantitative biochemical studies in the human subject.

Protein binding and kinetics of drugs in liver diseases

Although the liver is the major site for drug biotransformation, the effect of hepatic dysfunction on drug disposition has not been consistent or predictable. Most early studies of drug kinetics in liver disease measured only half-life. Only in the past few years has it been realised that liver diseases can affect drug absorption, hepatic metabolism, tissue distribution, and protein binding, which complicate interpretation of any change, or lack of change in drug half-life. Furthermore, it is now apparent that the efficiency with which a drug is metabolised by the liver, the extent of binding to blood constituents, and the aetiology and stage of the hepatic disorder are each important in determining whether significant alterations in drug disposition will occur. A pharmacokinetic perfusion model which takes into account many of the above factors has been proposed, and appears to be useful for predicting changes in the disposition of rapidly metabolised compounds. Nevertheless, the state of knowledge about those factors which limit the rate of metabolism of individual drugs or classes of drugs in inadequate, and no general model or guidelines which are useful clinically have been developed. Patients with hepatic disorders may show increases or decreases in sensitivity independent of alterations in drug disposition. The clinician caring for such patients must be cautious about the use of any drugs, and rely heavily on careful patient observation to determine efficacy or toxicity.

Michaëlis--Menten kinetics of phenazone elimination in the perfused pig liver

The purpose of the present study was to define the elimination kinetics of phenazone (NFN) in the isolated perfused pig liver. In five experiments phenazone was administered as constant infusion to obtain steady-state periods over a wide range of concentrations. The elimination of phenazone followed saturation kinetics (concentrations 0.1-12 mmol x 1(-1) and the maximal elimination rate (Vmax) was on average 102 mumol x min-1 x kg-1 liver and the Michaëlis-constant (Km) of 2.6 mmol x 1(-1). Estimates of Vmax and Km for the microsomal phenazone hydroxylase activity measured in liver biopsies found to be considerably lower than in the perfused liver. The hepatic elimination of phenazone during perfusion of pig liver at phenazone concentrations corresponding to human therapeutic doses follows first-order kinetics.

Assessment of antipyrine kinetics by measurement in saliva

The half-life of antipyrine has been estimated from saliva samples in ten subjects by a gas chromatographic method. Half-life, apparent volume of distribution and total body clearance estimated from saliva and plasma concentrations of antipyrine are not significantly different. The concentration of antipyrine in saliva is independent of flow rate within the range expected in healthy subjects in response to mechanical and sapid stimuli. Antipyrine estimation in saliva could facilitate many areas of phaamacokinetic research limited by the difficulty of obtaining serial plasma samples.

Comparison of the half-life of antipyrine in plasma, whole blood and saliva of man

A previously described GLC method has been modified and applied to measurement of antipyrine levels in plasma, blood and saliva of man following administration of a single oral dose (10 mg/kg). Tery time studied. The half-life of antipyrine determined in blood, plasma or saliva in any given individual was similar. The intersubject variation in half-life was about two-fold (n = 5). Antipyrine levels in saliva were not affected by the rate of saliva flow when collections were made continuously for 20 minutes. This study has demonstrated that kinetic data about antipyrine comparable to that from plasma may also be obtained from readily accessible tissue fluids, such as saliva and capillary blood.