Rapid Detection of the Antibiotic Sulfamethazine in Pig Body Fluids by Paper Spray Mass Spectrometry

We report herein a practical method for nonlethal detection of the antibiotic sulfamethazine in pig body fluids via the combination of simple extraction and paper spray mass spectrometry (PS-MS). This method requires minimal sample preparation while still providing high sensitivities and accuracies in complex matrices including pig whole blood (LOD = 7.9 μg/L; recovery = 95.4-103.7%), pig serum (LOD = 11.5 μg/L; recovery = 103.2-106.2%), and synthetic urine (LOD = 11.2 μg/L; recovery = 99.1-103.2%). Given a known correlation between the level of sulfamethazine in body fluids and edible tissues, this method shows great promise as a practical and nonlethal solution for rapid testing of the drug, which can substantially aid managerial decision in the livestock industry.

Influence of a five-day vegetarian diet on urinary levels of antibiotics and phthalate metabolites: a pilot study with "Temple Stay" participants

Diet is purported to be means of exposure to many environmental contaminants. The purpose of this study is to understand the influence of dietary change on the levels of exposure to several environmental chemicals - in particular, antibiotics and phthalates. For this purpose, we examined the extent to which short-term changes in diet influenced the inadvertent exposure levels to these chemicals in an adult population. We recruited participants (n=25) of a five-day 'Temple Stay' program in Korea and collected urine samples before and after the program. We also conducted a questionnaire survey on participants' dietary patterns prior to their participation. During the program, participants followed the daily routines of Buddhist monks and maintained a vegetarian diet. Urinary levels of three antibiotics and their major metabolites, metabolites of four major phthalates, and malondialdehyde (MDA) as an oxidative stress biomarker were analyzed. The frequency and levels of detection for antibiotics and phthalates noticeably decreased during the program. Urinary MDA levels were significantly lower than before program participation (0.16 versus 0.27mg/g creatinine). Although the exposure to target compounds might be influenced by other behavioral patterns, these results suggest that even short-term changes in dietary behavior may significantly decrease inadvertent exposure to antibiotics and phthalates and hence may reduce oxidative stress levels.

Preliminary evaluation of a lateral flow immunoassay device for screening urine samples for the presence of sulphamethazine

A lateral flow immunoassay (LFIA) device was developed and applied to testing urine samples for residues of the antimicrobial sulphamethazine (SMZ). This report describes the preparation of a rat monoclonal antibody to SMZ and its characterisation in an ELISA format. Apart from SMZ, the antibody showed high (> or =50%) cross-reactivity to N4-acetyl-sulphamethazine (55%), sulphamerazine (59%) and sulphisoxazole (50%) and lower cross-reactivity of 18% to sulphachlorpyridazine and sulphadiazine. The LFIA device consisted of a nitrocellulose membrane spotted with SMZ-ovalbumin and goat anti-mouse antibody as capture line and control line, respectively. Mouse anti-rat IgG F(ab')2 fragment specific antibody, adsorbed to colloidal carbon, was used as the detection ligand in the LFIA. The LFIA device had a cut-off value of 6.3 ng/ml in diluted (1/10) urine. Urine samples from SMZ-treated pigs, and bovine and porcine urine samples fortified with SMZ were used for a blind, four-laboratory evaluation of the performance of the LFIA device. Concentrations of SMZ in the test samples (n=29), as determined by LC-MS/MS, ranged from 0 (<3) to 1174 ng/ml. The evaluation of the LFIA device showed an overall sensitivity of 100%, a specificity of 71%, and positive and negative prediction values of 73% and 100%, respectively. The LFIA device has been fabricated as a test kit for determining SMZ residues in animals produced for slaughter.

[Diagnosis of acetylation phenotype in the protection of production personnel]

The authors elaborated noninvasive method to diagnose acetylation phenotype through photocolorimetric studying kinetics of sulfadimesine urinary excretion. Suggestion is approach to people protection through selection of inductors which purposefully increase individual activity of N-acetyltransferase.

Rapid and sensitive screening of sulfamethazine in porcine urine with an enzyme-linked immunosorbent assay and a field-portable immunofiltration assay

An enzyme-linked immunosorbent assay (ELISA) and an enzyme-linked immunofiltration assay (ELIFA) were developed for the screening of sulfamethazine (SMZ) in porcine urine. Incurred urine samples were measured by ELISA with a working range of 0 to 10 ng of SMZ per ml. The assay showed good accuracy and precision, with recoveries above 99.8% and intra- and interassay coefficients of variation (CVs) ranging from 2.6 to 5.6% and from 5.9 to 12.7%, respectively. Good agreement was observed when the results of the immunoassay were compared with those of liquid chromatography/tandem mass spectrometry analysis. For the ELIFA, a nylon membrane is placed on top of an absorbent material and covalently coated with rabbit anti-rat immunoglobulins. Free binding sites are blocked, and monoclonal anti-SMZ antibodies, SMZ standard or urine, and SMZ-horse radish peroxidase conjugate are subsequently dropped onto the membrane. During the assay, the reactants are drawn through the membrane because of its close contact with the absorbent pad. Finally, a substrate solution is added for blue color development. The blue spot produced can be visually evaluated or instrumentally measured (numeric deltaE*ab value), and the intensity of its color is inversely proportional to the analyte concentration. When a blue dot appears on the membrane, even if its color is less intense than that of the negative control, the sample is considered "negative," i.e., it is thought to contain a concentration of SMZ that is below the visual detection limit. If no color appears on the test membrane, the sample is considered "positive," i.e., it is thought to contain a concentration of SMZ that is equal to or above the visual detection limit. Validation of the assay showed good inter- and intra-assay precision (CV < 10%). Because samples can be analyzed after a simple dilution in <30 min with this assay format, it has strong potential for application in the field.

Pharmacokinetics and urinary excretion of sulphadimidine in buffalo calves

Pharmacokinetics and urinary excretion of sulphadimidine (SDI) were determined in buffalo calves following single oral administration (150 mg/kg). The plasma levels of free sulphadimidine were above minimum effective therapeutic concentration (> 40 micrograms/ml) between 4 and 12 h and the N4-acetylated form of the drug was in the range of 7.2-19.3%. Kinetic evaluation of plasma levels was performed using a two-compartment open model. The absorption and elimination half-lives of SDI were 3.01 and 11.94 h, respectively. Based on this study, an optimal dosage regimen of sulphadimidine in buffalo calves would be 100 mg/kg, followed by 50 mg/kg at 12 h intervals. Sulphadimidine was mainly excreted in the urine as free amine. The percentage of N4-acetyl sulphadimidine in urine was comparatively higher than in plasma.

Liquid chromatography tandem mass spectrometric quantitation of sulfamethazine and its metabolites: direct analysis of swine urine by triple quadrupole and by ion trap mass spectrometry

This work describes a new method for the quantitation of trace amounts of sulfamethazine (SMZ) and its main metabolite, N4-acetylsulfamethazine (Ac-SMZ), in swine urine, using high-performance liquid chromatography (HPLC) tandem mass spectrometric analysis of crude urine after addition of internal standard and simple dilution with water. The aim was to determine whether residues of this sulfamidic drug, normally administered to swine in order to prevent infectious diseases, were present in urine at levels lower than those permitted by regulatory authorities before human consumption (EU Project SMT, contract number CT 96-2092). A 10 microL volume of diluted urine was injected into a very short, narrow-bore chromatographic column (Zorbax SB-C18 2.1 i. d. x30 mm length, 3.5 microm pore size). Elution of the analytes of interest was achieved in less than seven minutes using a rapid gradient (from 20 to 80% methanol in 3 minutes). Either a PE Sciex API 365 triple quadrupole (QqQ), operated in the selected reaction monitoring (SRM) mode, or a Finnigan LCQ ion trap (IT) mass spectrometer, operated in narrow-range product ion scan, was used as the final detector. Electrospray (ESI) was used as the ionization technique. A comparison of the two tandem mass spectrometers was performed by analyzing the same set of test samples, at three concentration levels, on three different days. Linearity of responses of the calibration standards, intra- and inter-assay precision of the samples, specificity and limits of detection were evaluated for both systems. Both the QqQ and the IT instrument was suitable for rapid, sensitive and specific determination of the analytes, although the overall performance of the QqQ was slightly superior in terms of linearity, precision and sensitivity.

[Clinical significance of oxidation and acetylation genetic polymorphism in patients with Parkinson's disease]

The relationship between genetically determined polymorphic oxidation and acetylation and susceptibility to some disease has aroused much interest. The aim of our study was to evaluate whether patients with Parkinson's disease differ from healthy persons in their ability to oxidize sparteine and acetylate sulfadimidine as model drugs. Oxidation and acetylation phenotypes were estimated in 50 patients with Parkinson's disease. The control group consisted of 160 healthy volunteers for comparison of oxidation phenotype and 60 healthy volunteers for comparison of acetylation phenotype. The phenotyping of oxidation revealed two distinct populations among 50 patients with Parkinson's disease: 47 persons (94%) were extensive metabolizers of sparteine and 3 persons (6%) were poor metabolizers. In 160 healthy persons, 146 persons (91.2%) were extensive metabolizers of sparteine and 14 persons (8.8%) were poor metabolizers. The difference between frequency distribution of PMs and EMs in healthy persons and in patients with Parkinson's disease was not statistically significant. The phenotyping of acetylation showed among 50 patients with Parkinson's disease 38 persons (76%) slow acetylators and 12 persons (24%) rapid acetylators. In 60 healthy volunteers the phenotype of slow acetylation was observed in 29 persons (48.3%) and rapid acetylation in 31 persons (51.7%). The prevalence of slow acetylators among patients with Parkinson's disease in comparison to healthy volunteers was statistically significant (chi 2 = 8.7677/p < 0.003). The results of our study may suggest that the slow acetylation phenotype is associated with increased risk of the development of Parkinson's disease.

Development of a one step strip test for the detection of sulfadimidine residues

The one step strip test described is a competitive immunoassay in which the detector reagent consists of colloidal gold particles coated with affinity purified polyclonal anti-sulfadimidine (SDD) antibodies. The capture reagent in the assay is an SDD-ovalbumin conjugate which is immobilised on the lateral flow membrane of the test device. In the test procedure, 150 microliters (four drops) of a liquid sample (buffer, urine or milk) are brought into the sample well of the test device and allowed to migrate over the membrane. The more analyte present in the sample, the more effectively it will compete with the SDD immobilised on the membrane for binding to the limited amount of antibodies of the detector reagent. A sufficient amount of SDD in the sample will therefore prevent the binding of the detector reagent to the SDD immobilised on the membrane. Therefore, a positive sample will not show a test line in the read-out zone. With spiked buffer or calf urine this was obtained at a level of > 10 ng ml-1 of SDD and with spiked (diluted) fresh cow milk at a level > 20 ng ml-1 of SDD. At these levels, the test is applicable only as a qualitative assay. The presence or absence of a test line indicates lower or higher levels of SDD, respectively. The major advantages of the one step strip test are that results can be obtained within 10 min and that all reagents are included in the test device.

Application of an enzyme immunoassay for the determination of sulphamethazine (sulphadimidine) residues in swine urine and plasma and their use as predictors of the level in edible tissue

The potential of an enzyme immunoassay (EIA) with high cross-reactivity towards the major metabolite (N4-acetyl-sulphamethazine) of sulphamethazine was tested for screening fluids and tissues. Healthy pigs were given 20 mg sulphamethazine per kg body weight per day in their drinking water for 2 days. Groups of four pigs were slaughtered after 3, 4 and 7 days withdrawal. The results were compared with liquid chromatographic analysis for urine, plasma, kidney, liver, gluteal muscle and diaphragm. In general, concentrations found by the EIA were higher than those found by liquid chromatography (LC) because sulphamethazine metabolites were detected by the EIA and not by LC. Using the EIA for the detection of sulphamethazine and the major metabolite in urine and plasma, predictive relationships (tissue-fluid ratios) for the concentration of the parent drug in tissue, determined by LC, were calculated. The tissue-plasma ratios for muscle, liver and kidney were 0.1, 0.2 and 0.1, respectively. The tissue-urine ratios for muscle, liver and kidney were 0.02, 0.03 and 0.03, respectively. Owing to the higher concentration of the parent drug in both fluids, the presence of the major metabolite in urine and the sensitivity of the EIA, tissue can be screened for low concentrations of sulphamethazine.

[Clinical significance of the determination of oxidation and acetylation phenotype in patients with multiple sclerosis]

Genetically determined individual differences in the ability of oxidation and acetylation of certain drugs have raised in recent years a considerable interest in view of their clinical importance. The purpose of the study was finding out of a possible difference in the ability to oxidized sparteine and to acetylate sulfamidine as model drugs between patients with multiple sclerosis and healthy control volunteers. The study was carried out in 23 patients with MS. The control group comprised 160 healthy subjects for comparison of oxidation phenotype. The results of determination of acetylation phenotype were obtained in 45 healthy controls. The study showed that in 160 controls 146 were extensive (rapid) metabolizers (91.3%) and 14 were weak (slow) metabolizers of sparteine (8.7%). In the group of MS patients 21 were extensive metabolizers (91.3%) and 2 were weak metabolizers (8.7%). The determination of acetylation phenotype in 45 controls showed 51% of rapid acetylation (23 subjects) and 49% of slow acetylation (22.

The production of pig tissue sulphadimidine reference material

The production of stable homogeneous reference materials containing the antimicrobial agent sulphadimidine in pig tissue is described. These were commissioned by the Community Bureau of Reference (BCR), established by the Commission of the European Communities, to promote improvements in analytical accuracy and to ensure uniformity of results determined by member states. Sulphadimidine-containing tissue powders (400 vials each of muscle, liver and kidney) were prepared by orally dosing pigs with drug, producing lyophilized tissue powders and blending these with negative tissues from unmedicated animals to achieve target concentrations. Details of the production process, the stabilizing procedure developed and the analytical assessments of homogeneity and stability are given.

[Drug residues in untreated swine]

The concentration of sulfadimidine was measured in the urine of pigs which were housed (over five days) in boxes where other pigs have been treated orally with sulfadimidine before. Sulfadimidine was measured in the urine of the unmedicated pigs in a concentration of up to 4 micrograms/ml. Considering these urine concentrations, violative sulfadimidine tissue residues would be expectable in the carcass after slaughter. The practice of fixing withdrawal times must be considered again to ensure that drug residues in tissues are below the MRL before slaughter also in unmedicated animals.

Inhibition and induction of cytochrome P4502E1-catalyzed oxidation by isoniazid in humans

We studied the effect of isoniazid administration on the cytochrome P4502E1-catalyzed elimination of chlorzoxazone and acetaminophen. Isoniazid, 300 mg daily, was administered for 7 days to a group of 10 volunteer slow acetylators. Acetaminophen, 500 mg, and chlorzoxazone, 750 mg, were administered on separate occasions before isoniazid, during the period of isoniazid administration, and after the discontinuation of isoniazid. Isoniazid inhibited the clearance of chlorzoxazone by 58%, as assessed from plasma data, and inhibited the formation of acetaminophen thioether metabolites (a measure of the formation of the hepatotoxin N-acetyl-p-benzoquinone imine and catechol oxidative metabolites of acetaminophen, as determined from their recovery in urine, by 63% and 49%, respectively. Two days after the discontinuation of isoniazid, the clearance of chlorzoxazone was increased over the value before isoniazid by 56%. Acetaminophen thioether but not catechol metabolites were increased by 56% 1 day after the discontinuation of isoniazid and had returned to the pre-isoniazid value 3 days after the discontinuation of isoniazid. We conclude that the time course of the interaction with regard to chlorzoxazone elimination and formation is compatible with an inhibition-induction effect of isoniazid on cytochrome P4502E1. The mechanism of this biphasic effect is probably induction by protein stabilization, which results in inhibition of catalytic activity while isoniazid is present.

Sulfamethazine as a model compound to assess sex hormone-dependent cytochrome P-450 activity in rats

Plasma disposition and urinary recovery of sulfamethazine (SMZ), its N4-acetylated metabolite (N4AcSMZ), and two of its hydroxylated metabolites [5-hydroxysulfamethazine (5OHSMZ) and 6-hydroxymethylsulfamethazine (6CH2OHSMZ)] were determined in male and female rats, in castrated males, and in rats pretreated with various steroid hormones. Male rats had a 2-fold higher SMZ plasma clearance than females, castrates, and males treated with flutamide (a testosterone antagonist). When castrated male rats were treated with testosterone or trenbolone, SMZ plasma clearance returned to normal values. Higher SMZ plasma clearance rates in the presence of androgens went together with higher urinary recoveries of the 6CH2OHSMZ metabolite. In hepatic microsomes of male rats lower apparent KM values, and higher Vmax values for 6CH2OHSMZ and 5OHSMZ formation were found than in microsomes of female rats. Castration or treatment of male rats with flutamide markedly reduced microsomal SMZ hydroxylation rates. Pretreatment of male or female rats with phenobarbital or triacetyl-oleandomycin had no effect on microsomal SMZ hydroxylation, whereas a continuous infusion with bovine somatotropin in male rats caused a marked decrease in SMZ hydroxylation rate. Finally, SMZ hydroxylation to 6CH2OHSMZ and 5OHSMZ in hepatic microsomes from male rats was strongly inhibited by monoclonal antibodies against P-4502C11. These results suggest that the male-specific P-4502C11 enzyme plays an important role in the hydroxylation of SMZ to 6CH2OHSMZ and 5OHSMZ in rats. SMZ seems a useful model compound to assess hormone effects on oxidative biotransformation (in vivo and in vitro) in rats.

The regulation of oxidative drug metabolism by growth hormone in the dwarf goat: differences from and similarities to the mechanisms in rats

The effects of bovine GH (BST), administered in different dose patterns, on in-vivo oxidative drug metabolism, were studied in female dwarf goats. Animals received recombinantly derived methionyl BST at a dose of 500 micrograms/kg body weight per 24 h for 6 days. It was administered to one group of goats as one s.c. injection per day, another group received a similar 24-h dose divided into three s.c. injections given at 8-h intervals, and the third group received 50 micrograms BST/kg body weight every 2.5 h by a pulsative i.v. infusion. Oxidative metabolic capacity was assessed by determining plasma sulphadimidine (SDD) elimination and urinary metabolite excretion. SDD shows a marked sex-dependent plasma elimination in dwarf goats, with male goats having a lower plasma clearance than female goats. When BST was given by daily injection, no clear effects on SDD plasma clearance or urinary metabolite excretion were observed. However, when the total dose was divided into three injections given at 8-h intervals, the plasma SDD elimination rate decreased. This was associated with a decrease in urinary excretion of the two main hydroxy SDD metabolites. When BST was given by discontinuous i.v. infusion, simulating the male endogenous plasma GH pattern, a marked decrease in SDD plasma clearance was observed. In addition, the excretion of the two urinary hydroxy metabolites was considerably reduced. These results suggest that GH can affect drug oxidation in dwarf goats via mechanisms similar to those suggested for rats. However, in the dwarf goat, the sex differences in drug metabolism are opposite to those in rats.

Isoniazid induced neuropathy in slow versus rapid acetylators: an electrophysiological study

Clinical, biochemical and nerve conduction studies were performed in 100 cases of tuberculosis taking isonicotinic acid hydrozide (isoniazid) for more than 12 weeks. Electro-physiological studies were carried out in a similar number of normal age and sex matched controls. In 16 percent of cases an abnormality was documented in the motor nerve conduction velocity, amplitude and terminal latency of the common peroneal, ulnar and median nerves; of these, only two patients had objective evidence of neuritis. The occurrence of isoniazid neuropathy was found to be more in the fourth decade of life (10 of 16), in those who had taken the drug for over six months (13 of 16), and in 'slow' inactivators (10 of 16).

The effect of moderate haemodilution with Fluosol-DA or Hespan on the nonmicrosomal acetylation of sulphadimidine in the rat

The effects of Fluosol-DA (Fluosol) and Hespan haemodilution on the nonmicrosomal acetylation of sulphadimidine were studied in male rats. Fluosol increased the acetylsulphadimidine percent excreted in urine, the metabolic formation rate constant (kf), and the formation clearance (CLF) for 72 h after haemodilution without any significant changes in the sulphadimidine apparent volume of distribution (Vd) or total body clearance (CL). Hespan haemodilution increased the acetylsulphadimidine percent excreted in urine only at 48 h while significantly decreasing the sulphadimidine clearance, urinary excretion rate constant (ku), and renal clearance (CLR) for 72 h. The enhanced N-acetyltransferase activity after Fluosol haemodilution may have therapeutic consequences for concomitantly given drugs metabolized by this enzyme.

N-acetylation and oxidative capacity in aged volunteers determined with sulfamethazine and antipyrine

The elimination of antipyrine (AP 15 mg/kg) and sulfamethazine (SM 500 mg) was measured in healthy volunteers of rapid and slow acetylator phenotype. Nineteen males were 20-32 years of age, 11 males and 6 females between 62-86 years of age. Apparent volume of distribution of AP was reduced in advanced age independent of the acetylator status of the individuals. Total body clearance was significantly lower and half-time and mean residence time were higher only in slow but not in rapid acetylators. In the elderly of both phenotypes, the acetylation ratios of SM were significantly enhanced. Renal and metabolic clearance were decreased and AUC-values of SM and its acetylated metabolite were increased in slow but unchanged in rapid acetylators. Physiological peculiarities of distribution and renal excretion of SM and its acetylated metabolite in advanced age may have caused the contradictory results.

High-performance liquid chromatographic method for the routine determination of sulphadimidine, its hydroxy metabolites and N4-acetylsulphadimidine in body fluids and cell culture media

A simple high-performance liquid chromatographic method is presented for the determination of trace amounts of sulphadimidine (SDD), its hydroxylated metabolites and N4-acetyl-SDD in blood plasma, urine, hepatocyte culture media and microsomal incubations. The synthesis of 5-hydroxy-SDD and an improved method for the isolation of 4-methylhydroxy-SDD from urine are described and their respective specific absorption coefficients at 265 nm are calculated by on-line radiochemical and ultraviolet detection. The limit of detection of the analytical method is 0.05 micrograms/ml for SDD and its hydroxy metabolites and 0.2 micrograms/ml for N4-acetyl-SDD. Linear calibration graphs for SDD and its metabolites were constructed from 0.2 to 50 micrograms/ml. The method has been applied to biotransformation studies in vivo and in vitro.

Caffeine as a metabolic probe: validation of its use for acetylator phenotyping

The use of two caffeine metabolite ratios for acetylator phenotyping was validated by demonstrating concordance with two sulfamethazine tests in 178 unrelated healthy subjects. The caffeine metabolites used for this purpose were 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X), and 1-methylurate (1U). The ratio AAMU/(AAMU + 1X + 1U), referred to as molar ratio or N-acetyltransferase, was compared with the ratio AAMU/1X. The results indicated that, for screening purposes, the acetylator phenotype can be determined by analysis of a 6-hour urine sample after a cup of coffee or strong tea or a can of caffeine-containing soft drink. The ratio AAMU/1X is the ratio of choice for the study of subjects in whom variability of xanthine oxidase can be neglected; use of the ratio AAMU/(AAMU + 1X + 1U) appears appropriate for special purposes. Gender, ethnic origin, habitual or moderate consumption of coffee, tea, soft drinks, or ethanol, or cigarette smoking have little if any effect on the caffeine tests for acetylator phenotyping.

N-acetylation in healthy and diseased children

Acetylation capacity was examined in three groups of Czech children by measuring the plasma and urine concentrations of sulphamethazine and its acetylated metabolite 6 h after an oral test dose of 20 mg/kg sulphamethazine. Amongst 82 healthy children aged 4-15 y there were 32 (39%) fast acetylators; there was no significant difference between the number of boys and girls, or between children over or less than 6 years of age. In 41 patients aged 3-15 y with phenylketonuria, the acetylation indices showed a significantly higher proportion of fast acetylators - 24 (58.5%) using plasma measurements and 29 (70.7%) using urine data. In them the ratio between slow and fast acetylators was inverted compared to normal children. The preponderance of fast acetylators was greater in boys than in girls and in children over 6 years of age. An increased acetylation capacity in patients with phenylketonuria was apparent even in individuals classified as slow acetylators, because in them the plasma concentration of the acetylated metabolite was higher than in control acetylators. Amongst 48 young patients (5-15 y) with insulin-dependent diabetes there were 19 (39.6%) fast and 29 (60.4%) slow acetylators, which corresponded well to the phenotype distribution in control children. This did not support the suggested association between the fast acetylator phenotype and Type I diabetes.

Pharmacokinetics of sulfadimidine and its N4-acetyl metabolite in healthy and diseased rabbits infected with Pasteurella multocida

The pharmacokinetics of sulfadimidine (SDM) and its N4-acetyl metabolite (N4SDM) were investigated after intravenous bolus injection of a single dose (200 mg/kg) of SDM in normal and diseased New Zealand white rabbits. The apparent distribution volume at steady state, total body clearance and elimination half-life of SDM in normal animals were 0.7 +/- 0.3 l/kg, 0.57 +/- 0.24 l/kg/h and 1.6 +/- 1.3 h, respectively. Of the administered dose, 62.1% was metabolized by N4-acetylation, and 12.7 +/- 1.1 and 2.8 +/- 1.8% of the dose was excreted as free drug by the kidney and gastrointestinal tract, respectively. The 'apparent' formation and elimination half-lives of N4SDM were 0.6 +/- 0.4 and 2.2 +/- 1.1 h, respectively. The metabolite was eliminated mainly by excretion through the kidney. There was no significant effect of acute pasteurellosis on the pharmacokinetics of either SDM or N4SDM in rabbits.

Carry-over of sulphadimidine in the faeces and urine of pigs fed medicated feed

In two experiments sulphadimidine-free pigs were placed in pens previously occupied by pigs fed a diet containing 100 ppm sulphadimidine. Faeces, urine and spilled feed had been removed by scraping the surface of the pens before the new pigs were introduced. The concentration of sulphadimidine in the tissues of the medicated pigs fell below 100 ng/g within 72 hours of withdrawal of the medicated diet and in the fluids the concentration fell below 500 ng/ml within 96 hours. The concentrations in the tissues of the pigs housed in the contaminated pens exceeded 100 ng/g for up to 24 hours but then fell to acceptable concentrations; the concentration of sulphadimidine in body fluids occasionally exceeded 500 ng/ml.

Sulphadimidine in the urine of experimentally fed pigs

An enzyme-linked immunoassay for the detection of sulphadimidine in unextracted pig urine is described. Twenty-four hour urine samples from six individually caged pigs, four treated and two controls, were examined during a 10-day treatment and a 12-day withdrawal period. The concentration of sulphadimidine in the urine of the treated pigs increased rapidly after feeding started and decreased on withdrawal. The maximum concentration in a control pig was 308 ng/ml, and this concentration was probably due to contamination of the environment. By the seventh day after withdrawal of the drug its concentration in the urine of the treated pigs was less than 500 ng/ml.

The effect of streptozotocin-induced diabetes on the in vivo acetylation capacity and the in vitro blood N-acetyltransferase activity of the adult male Sprague-Dawley rat

Induction of experimental diabetes using streptozotocin significantly reduced the extent of sulphamethazine acetylation by Sprague-Dawley rats. This treatment did not significantly change the total amount of sulphonomide excreted in the urine. The in vitro blood N-acetyltransferase activity of rats treated with streptozotocin was significantly higher than that of untreated animals. Increasing the in vitro glucose concentration of blood samples from both groups significantly increased the amount of acetylsulphamethazine produced.

Pantothenic acid, acute ethanol consumption and sulphadimidine acetylation

The effect of pantothenic acid and acute ethanol loading on the genetically determined N-acetyltransferase activity has been studied using sulphadimidine as a test substance. The administration of 1100 mg pantothenic acid daily (600 mg orally, 500 mg iv) for seven days did not significantly alter sulphadimidine kinetics in the primarily elderly 21 subjects we investigated. Acute ethanol loading (0.73 g/kg pure alcohol at start and 0.11 g/kg pure alcohol hourly for 8 hours afterwards, stock solution: 20% v/v ethanol in fruit juice) did not change sulphadimidine acetylation in 10 healthy male volunteers. It is concluded that despite theoretical assumptions exogenous factors like pantothenic acid and ethanol do not significantly influence the cytosolic N-acetyltransferase activity. Consequently they do not interfere with the acetylator phenotyping procedure.

Acetylation polymorphism and leprosy

The sulfones are the drug of choice in the treatment of leprosy, with dapsone as the clear favorite. The major route for dapsone metabolism leading to its inactivation and excretion is via acetylation by hepatic N-acetyl transferase (NAT), as is the case with isoniazid (INH) and sulfamethazine (SMZ). The enzyme is known to exhibit genetic polymorphism. The object of the present study is mainly to determine the incidence of acetylator phenotype in a population of leprosy patients with a view to evaluating the degree of association, if any, between phenotype and the disease. Obviously a knowledge of the incidence of the phenotypes may provide a valuable contribution to the institution of more rational and successful therapy. In the normal or control subjects, as well as in the leprosy patients, the frequency distribution histograms of the percentage acetylsulfamethazine in urine and serum samples are bimodal, and this indicates the existence of a genetic polymorphism. Based on the bimodality, individuals were classified as either "rapid" or "slow" acetylators, and the incidence of the slow acetylator phenotype of about 51% was observed in the leprosy population. This gives a relatively high incidence of the allele controlling the slow acetylator (q = 0.73). Although there is evidence that the mean percentage of SMZ acetylated in leprosy patients of the slow acetylator phenotype is significantly higher than that observed for the same phenotype in the controls (t = 4.86, P less than 0.02), statistical analyses show that there is no association between the slow acetylator phenotype and the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

N-acetylation phenotyping with sulphadimidine in a Turkish population

The distribution of acetylator phenotypes was studied in 244 unrelated Turkish subjects. Sulphadimidine and its acetylated metabolite were measured in 6 h plasma and 0-6 h urine samples after an oral dose of 10 mg/kg. Subjects with 37.5% or less acetylsulphadimidine in plasma were regarded as slow acetylators and the others as rapid acetylators. The mean plasma concentration of acetylsulphadimidine was about 2.5-times lower in slow acetylators. Urinary excretion of total sulphadimidine (free + acetylated) was also significantly lower in slow acetylators compared to rapid acetylators. The frequency of slow acetylators was 60.7% in the population (95% confidence interval 54.3% to 66.8%). Sulphadimidine acetylation showed no variation due to sex, age, body weight or pre-existing disease.

Acetylator phenotype and congenital malformations

The hypothesis has been tested that an unusual maternal acetylator phenotype can predispose to congenital malformations in the fetus. The acetylator phenotype of normal caucasian control women and of mothers of malformed children was established by measuring urinary sulphadimidine and its acetylated metabolite. A further control group was the fathers of the malformed newborn. The malformations studied were facial-cleft, spina-bifida and congenital heart disease. The acetylator phenotype was shown not be modified by pregnancy. 49 of 100 (49%) control women were rapid acetylators. Amongst the 108 mothers of malformed babies, 56 (52.8%) were slow acetylators and 52 (47.2%) were fast acetylators, 42 out of 83 (50.5%) of the fathers of malformed were slow acetylators and 41 (49.5%) were fast acetylators. Thus, the acetylator phenotype of the mothers of malformed children is no different from the acetylator phenotype of controls.

Effect of intra-articular glucocorticoids on the disposition of sulphadimidine in chronic osteoarthritis patients

1. The disposition of sulphadimidine (15 mg kg-1 orally) was investigated in six chronic osteoarthritis patients (four slow and two fast acetylators) prior to and 4 days following intra-articular administration of glucocorticoids. 2. The mean (+/- s.e. mean) renal clearance of sulphadimidine was increased from 0.03 +/- 0.01 to 0.07 +/- 0.02 ml min-1 kg-1 (P = 0.01) following the administration of intra-articular steroid. 3. Mean metabolic clearance and volume of distribution data were similar on the two study days. However, two of the slow acetylators showed marked increases (63% and 193%) in metabolic clearance following steroid treatment.

Competitive direct enzyme-linked immunosorbent assay for detection of sulfamethazine residues in swine urine and muscle tissue

A sensitive assay for the detection of sulfamethazine in swine urine and muscle tissue using a direct competitive enzyme-linked immunosorbent assay (ELISA) has been developed. Undiluted urine or a phosphate-buffered saline extract of pork muscle tissue is mixed with an enzyme-labeled conjugate of sulfamethazine and horseradish peroxidase. The mixture is added to wells of a microtiter plate coated with antibody to sulfamethazine. After the test system is incubated, washed, and re-incubated with substrate and the reaction is stopped, the absorbance is measured at 405 nm. Levels of sulfamethazine as low as 20 ng sulfamethazine/g muscle tissue and 10 ng sulfamethazine/mL swine urine were detected and estimated.

The effect of food deprivation on the rate of sulfamethazine elimination in goats

The disposition kinetics and cumulative urinary excretion of sulfamethazine were compared in goats fed normally (control) and following a 72-hour period of starvation (fasting). The only pharmacokinetic parameter which showed a statistically significant difference between the two groups was the body (systemic) clearance. This decreased from 2.26 +/- 0.28 ml/min.kg (means +/- SD, n = 6) in the control group to 1.16 +/- 0.54 ml/min.kg in the fasting group (p less than 0.01). Since the apparent volume of distribution was not affected by starvation, the decreased clearance was attributed to slower metabolism of the drug. Because of the analytical method used to measure sulfamethazine concentrations in plasma and urine, no conclusion could be drawn as to whether the rates of hydroxylation or of acetylation, or both metabolic pathways were decreased in the starved condition.

N1-glucosides as urinary metabolites of sulphadimidine, sulphamerazine and sulphamethoxazole

The synthesis and characterisation of the N1-beta-D-glucosides of the three title sulphonamides are described, and these conjugates are shown, by means of HPLC and MS, to be minor urinary metabolites of these drugs.

Comparison between serum isonicotinic acid hydrazide (INH) levels and urinary sulfadimidine (sulfamethazine) acetylation as predictors of INH acetylator status

The acetylator status of 40 children with pulmonary tuberculosis was investigated by (1) sulfadimidine (SDM; sulfamethazine) acetylation test in urine and (2) estimation of isonicotinic acid hydrazide (INH) levels. The antimode was at 70% based on the frequency distribution of SDM acetylation. Children acetylating less than 70% of administered SDM were taken as slow acetylators while those with more than 70% as rapid acetylators. The serum INH antimode was at 0.85 micrograms/ml. Thus serum values less than 0.85 micrograms/ml categorised a child as rapid and those with more than 0.85 micrograms/ml as slow acetylators. The sensitivity of these two methods was similar with a correlation coefficient r = 0.64. Thus the determination of the type of acetylator by SDM acetylation test is equally reliable and technically simpler and is recommended instead of INH serum concentration.

Polymorphic acetylation of sulphamethazine in a Zimbabwe population

Sulphamethazine, 8 mg/kg body weight, was administered orally in tablet form to 100 healthy volunteers and total and free sulphamethazine were determined in the six hour urine sample. The bimodal population frequency distribution for percentage acetylated sulphamethazine showed 42 of the tested population to be fast and 58 to be slow acetylators, that is, an estimation of q = 0.72 +/- 0.3 as the frequency of the allele controlling slow acetylation. The study also revealed ample evidence that the assay of the drug in urine can be done in a significantly shorter time.

The effect of tick-borne fever on metabolism and renal clearance of sulfadimidine in goats

The tick-borne fever (TBF) model was used to study the effect of fever on the metabolism of sulfadimidine in goats. During TBF the elimination half-lives were prolonged, and the renal clearance values of sulfadimidine and the majority of its metabolites were markedly diminished compared with those in the uninfected state. During TBF the steady-state levels of the hydroxy metabolites were markedly increased. TBF reduced the extent of hydroxymethylation of the pyrimidine side chain; TBF did not affect acetylation of sulfadimidine. In one goat a progressive accumulation of the metabolites was noticed.

Pharmacokinetics, metabolism, and renal excretion of sulfadimidine and its N4-acetyl and hydroxy metabolites in humans

Sulfadimidine is acetylated and hydroxylated in humans. The hydroxylation pathways account for 10-20% of the dose, leaving the acetylation as the major metabolic pathway. The hydroxylation pathways are independent of the acetylator phenotype. The plasma concentration-time curve of sulfadimidine in fast acetylators is biphasic, with half-lives of 1.7 and 5.4 h, whereas that in slow acetylators is monophasic, with a half-life of 7.6 h. Hydroxylation of a methyl group in sulfadimidine lowers the protein binding from 90 to 60%, while acetylation does not affect the protein binding. Methyl hydroxylation markedly increases the renal clearance.

Acetylator phenotype among individuals with glucose 6-phosphate dehydrogenase variants

The acetylator phenotype was determined for 142 Nigerian adults by administering sulphamethazine (40 mg/kg body wt) and analysing six hour urines for free and acetylated drug. Of these 142 subjects, 21 (14.8%) had no red cell glucose 6-phosphate dehydrogenase activity, 35 (24.6%) had partial activity and 86 (60.56%) had normal activity. The percentage of slow acetylators among the three groups was 38.1%, 40% and 40.7% respectively. The differences between the three groups were not statistically significant. However, individuals with no red cell glucose 6-phosphate dehydrogenase activity and who are also slow acetylators may be more sensitive to the effects of drugs like sulphamethazine, dapsone and isoniazid.

Pharmacokinetics, renal clearance, tissue distribution, and residue aspects of sulphadimidine and its N4-acetyl metabolite in pigs

Pharmacokinetics and tissue distribution experiments were conducted in pigs to which sulphadimidine (SDM) was administered intravenously, orally, and intramuscularly at a dosage of 20 mg SDM/kg. SDM was acetylated extensively, but neither hydroxy metabolites nor their derivatives could be detected in plasma, edible tissues or urine. Following i.v. and two oral routes of administration, the N4-acetylsulphadimidine (N4-SDM) concentration-time curve runs parallel to that of SDM. The percentage of N4-SDM in plasma was in the range between 7 and 13.5% of the total sulphonamide concentration. The bioavailability of SDM administered in a drench was 88.9 +/- 5.4% and administered mixed with pelleted feed for 3 consecutive days it was 48.0 +/- 11.5%. The renal clearance of unbound SDM, which was urine flow related, was 1/7 of that of creatinine, indicating reabsorption of the parent drug. The unbound N4-SDM was eliminated three times faster than creatinine, indicating that tubular secretion was the predominant mechanism of excretion. After i.v. administration, 51.9% of the administered dose was recovered in urine within 72 h p.i., one quarter of which as SDM and three quarters as N4-SDM. Tissue distribution data obtained at 26, 74, 168, and 218 h after i.m. injection revealed that the highest SDM concentration was found in plasma. The SDM concentration in muscle, liver, and kidney ranged from one third to one fifth of that in plasma. The N4-SDM formed a minor part of the sulphonamide content in edible tissues, in which the SDM as well as the N4-SDM concentration parallelled the plasma concentrations. Negative results obtained with a semi-quantitative bioassay method, based on monitoring of urine or plasma, revealed that the SDM concentration levels in edible tissues were in that case below 0.1 mu/g tissue.

Depletion kinetics of 14C-sulfamethazine [4-amino-N-(4, 6-dimethyl-2-pyrimidinyl)benzene[U-14C]sulfonamide] metabolism in swine

Swine weighing 60-70 kg were orally administered 14C-sulfamethazine [4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzene[U-14C]sulfonamide] at 12-hr intervals for 7 days (165 mg/dose; 0.126-5.04 mCi/mmol). The animals were sacrificed at 8 hr or 2, 5, or 10 days after the last dose was given and tissues were assayed for total 14C activity. The presence of 14C-labeled sulfamethazine, N4-acetylsulfamethazine, desaminosulfamethazine, and the N4-glucose conjugate of sulfamethazine in blood, liver, kidney, skeletal muscle, and adipose tissue was verified by HPLC and GC-MS analysis. Total 14C residue levels in all tissues examined had dropped to less than 0.1 ppm sulfamethazine equivalents by day 10 of the depletion period. The mean half-life (t1/2) for sulfamethazine, the N4-glucose conjugate of sulfamethazine, and N4-acetylsulfamethazine was estimated to be 0.8 day. In some tissues, the depletion of the N4-glucose conjugate of sulfamethazine and N4-acetylsulfamethazine had decreased significantly between days 5 and 10, resulting in an approximate doubling of the t1/2 for that period. In contrast, the half-life of desaminosulfamethazine varied from a mean of 0.96 day during the 8-hr-5-day depletion period to 3.7-9.1 days during the 5- 10-day depletion period. In most tissues, the t1/2 for the 14C-activity in the methanol-insoluble fraction increased by 3-5-fold between days 5 and 10 of the depletion period. No predictable relationship was observed between blood sulfamethazine or metabolite levels and total residue levels in the tissues.

Effect of concomitant isoniazid administration on determination of acetylator phenotype by sulphadimidine

The influence of concomitant administration of isoniazid (INH) on the acetylation of sulphadimidine has been studied in 6 healthy volunteers, previously identified as having the fast acetylator phenotype. INH was administered in a slow release form (500 mg tablet) 1 hour before the sulphadimidine. Acetylation of sulphadimidine was measured in plasma 6 h after its intake and in urine collected between 5 and 6 hours. INH significantly decreased the acetylated fraction of sulphadimidine in plasma from 69.0 to 54.0 and in urine from 85.9 to 81.2%. This was reflected in a significantly higher plasma concentration of unconjugated sulphadimidine and reduced urinary excretion of acetylated sulphadimidine. It is concluded that concomitant administration of INH inhibits acetylation of sulphadimidine. Fast acetylators at the border line of discrimination, may be misclassified if phenotyped with sulphadimidine during concomitant administration of INH.

Effect of exercise on plasma levels and urinary excretion of sulphadimidine and procainamide

The pharmacokinetics of sulphadimidine (n = 9) and procainamide (n = 8), drugs which showed typical polymorphic acetylation rate, were studied in healthy volunteers subjected to intense physical exercise and bed rest for 4 hours in a cross-over manner. The exercise and the rest began 3 hours after giving procainamide and 4 hours after the administration of sulphadimidine, when the drug absorption had subsided. In rapid acetylators, the exercise raised both acetylated and non-acetylated sulphadimidine concentrations in serum, compared to rest values. With procainamide the rise was insignificant. In slow acetylators, the exercise revealed a significant difference in the procainamide group but not in sulphadimidine group. The exercise did not influence the acetylation degree of either of the drugs. Neither did it affect the protein binding of sulphadimidine. The urinary excretions of procainamide and acetylprocainamide were reduced by exercise generally more than those of sulphadimidine and acetylsulphadimidine. Endogenous creatinine clearance was reduced to 66%, whereas the renal clearances of sulphadimidine, acetylsulphadimidine and procainamide decreased to 89%, 48% and 16%, respectively. The results agree with our previous findings that physical stress can result in increased serum drug levels. Exercise does not seem to change the acetylation rate nor the protein binding of drugs, but it suppresses their excretion in urine, occasionally even more than what would be expected on the basis of the decrease in the glomerular filtration rate.

Identification and quantitation of sulfamethazine metabolites by liquid chromatography and gas chromatography-mass spectrometry

Methods for the identification and quantitation of carbon-14 labeled sulfamethazine [4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide], N4-acetylsulfamethazine, the N4-glucose conjugate of sulfamethazine, and desaminosulfamethazine in swine tissue are described. Tissues are ground and extracted with methanol, and the 14C-labeled compounds are purified by XAD-2 column chromatography and C-18 reverse phase liquid chromatography (LC) and the 14C-labeled compounds are then methylated and identified by gas chromatography-mass spectrometry analysis. Quantitation is accomplished by measuring the amount of 14C-activity that cochromatographs (C-18 reverse phase LC) with reference compounds.

Drug acetylation and expression of lupus erythematosus

Acetylator phenotype was measure in 58 patients presenting to a skin clinic with discoid lupus erythematosus (DLE) and in 51 normal healthy subjects. Twenty seven of the patients with DLE were found to have evidence of systemic lupus erythematosus (D+SLE). Frequency of slow acetylator phenotype was 58% in all DLE patients, 52% in those with D+SLE and was no different from the 57% in controls. The distribution of acetylator phenotypes within the groups with DLE and those with D+SLE was similar to controls. Severity of DLE was assessed as number of skin lesions and median lesion count was 11.5 in slow acetylators and 10 in fast acetylators but in D+SLE median lesion count was 22 in slow acetylators and 12 in fast acetylators, and there was a significant inverse relationship between lesion count and rate of acetylation; scores for systemic involvement showed no relationship. We conclude that there is no difference in the frequency or distribution of slow acetylator phenotype between normal subjects and patients with DLE with or without SLE but that actual rate of acetylation may determine severity of expression of the disease in slow acetylators.

Correlation of sulphadimidine acetylation test in urine and blood for isoniazid phenotyping

Sulphadimidine acetylation was determined in 110 cases in samples obtained from urine and blood. A trimodal distribution was observed by both the methods. The correlation co-efficient "r" for the two methods was 0.46.

Pharmacokinetics of sulfamethazine in male, female and castrated male swine

The concentration of sulfamethazine in plasma and sulfamethazine and its metabolites in urine were compared in male, female and castrated male swine. A surgical technique for placement of catheters in the urinary bladder was used to facilitate the collection of urine in males and castrated males. The elimination rate of sulfamethazine from plasma and the excretion of parent drug and metabolites into urine did not differ significantly among females, males and castrated male swine.