[Distribution of acetylator phenotypes in the Moscow population]

The data concerning distribution of acetylator phenotypes in Moscow city population are presented. 169 adults (96 women and 73 men) were tested by the Evans' method. The percentages of rapid and slow acetylators were 48 and 52%, respectively.

Pharmacokinetics and urinary excretion of sulphadimidine in sheep during summer and winter

Pharmacokinetics and urinary excretion of sulphadimidine were investigated in sheep during summer and winter seasons. Average minimum and maximum environmental temperature in the summer ranged from 22.6 to 40.2 degrees C and in winter from 4.5 to 21.1 degrees C. The determination of plasma volume, plasma protein and packed cell volume during summer and winter revealed a significant decrease in plasma volume and a significant increase in plasma protein in the summer indicative of haemoconcentration. Packed cell volume did not differ significantly between the seasons. The pharmacokinetics of sulphadimidine were determined following a single intravenous injection (100 mg/kg) in summer and winter. Zero time plasma concentration of the drug was higher during summer than in winter. The elimination half-life of the drug was similar in summer and winter, but the apparent volume of distribution was lower in summer. Likewise, total body clearance was significantly lower in summer. Based on these studies a satisfactory intravenous dosage regimen might consist of 86 and 100 mg/kg for priming and 78 and 88 mg/kg as maintenance doses during summer and winter, respectively, the doses being repeated at 12 hour intervals. Twenty four hours after sulphadimidine administration 90 and 73 per cent of the dose was excreted in urine during summer and winter, respectively. The drug was excreted mainly as free amine.

Influence of chronic obstructive lung disease on the disposition of an acidic drug (sulfamethazine)

The influence of chronic respiratory failure (CRF) on the pharmacokinetics of an acidic drug has been studied in 11 patients and in eight normal volunteers who received 10 mg/kg of oral sulfamethazine. Blood and urine samples were collected for 24 and 48 hours, respectively. No differences were observed in the rate of sulfamethazine absorption, but bioavailability was decreased when compared with control subjects. Sulfamethazine volume of distribution (Vd) was larger in patients than in control subjects. These differences in Vd may be secondary to an increase in sulfamethazine unbound fraction. No differences were observed in sulfamethazine elimination. It is concluded that in patients with CRF sulfamethazine bioavailability decreases, and Vd increases secondary to a decrease in binding. Despite the fact that plasma concentrations of the test drug will be decreased, the administration of higher doses may not be advisable.

Disposition kinetics and urinary excretion of sulphadimidine in normal and alloxan diabetic dogs

Disposition kinetics and urinary excretion of sulphadimidine were investigated in 16 dogs following a single intravenous injection (100 mg/kg body weight). Biochemical parameters including blood pH, blood glucose, plasma triglycerides and total plasma proteins of these animals were determined. The animals were injected alloxan (125 mg/kg) intravenously and when blood glucose level exceeded 300 mg%, the biochemical parameters, disposition kinetics and urinary excretion of sulphadimidine were determined again. After alloxan treatment of the dogs, there was a highly significant (P less than 0.01) decrease in blood pH, increase in blood glucose and plasma triglycerides levels when compared with the pretreatment values. The alloxan diabetic dogs showed a highly significant (P less than 0.01) reduction in elimination half-life (t1/2 beta) and apparent volume of distribution (Vd(area)) and increase in overall elimination rate constant (kel), total body clearance (ClB) and percentage of sulphadimidine dose excreted in urine. In normal dogs, one-half of the intravenous dose and after alloxan treatment two-third of the dose was eliminated through urinary excretion during 48 hours after injection. This study shows that the metabolic alterations of alloxan induced diabetes in dogs, influence the drug disposition and urinary excretion which indicate the need for the adjustment of dosage regimen in such metabolic disorders.

Trace analysis of sulfamethazine in animal feed, human urine, and wastewater by electron capture gas chromatography

Sulfamethazine, a widely used antibacterial drug additive in feeds for swine, chickens, and cattle, was scheduled for toxicological evaluation because of potential human health hazards associated with its residues in edible animal tissues. Analytical chemical procedures that would ensure proper concentration, homogeneity, and stability of the drug in dosed feed and its safe usage during the animal studies were prerequisites for such toxicological tests. Electron capture gas chromatographic (EC/GC) methods were therefore devised for the analysis of sulfamethazine residues in animal feed, human urine, and wastewater at levels as low as 100, 10, and 10 ppb, respectively. Sample extracts were cleaned up by using liquid/liquid partitioning, and the extracts were subjected to two derivatizations followed by cleanup on a silica gel column. The derivatizations of sulfamethazine consisted of methylation followed by trifluoroacetylation of the primary amine function. Ancillary data concerning stability of the compound in animal feed, water, and as a dry residue on glass, extraction efficiencies, partition values with various solvents, and the analysis of residues in feed by high pressure liquid chromatography (HPLC) at levels as low as 1.0 ppm are presented.

The isolation and identification of 14C-sulfamethazine (4-amino-n-(4,6-dimethyl-2-pyrimidinyl)[14C]benzenesulfonamide) metabolites in the tissues and excreta of swine

Pigs were given a single oral dose of 14C-sulfamethazine (4-amino-N(I4,6-dimethyl-2-pyrimidinyl)[14C]benzenesulfonamide). Approximately 78% of the 14C was eliminated in the urine and 18% was eliminated in the feces within 192 hr after dosing. The percentage of the 14C remaining in the animals after dosing was as follows: 6 hr, 88%; 24 hr, 49%; 48 hr, 14%; 192 hr, less than 1%. The 14C-labeled compounds in the tissues and excreta were isolated by solvent extraction and by conventional and high-pressure liquid chromatography, and then derivatized and characterized by infrared and mass-spectral analysis. Chemical structures were confirmed by synthesis. The major 14C-labeled compounds in the skeletal muscle, liver and kidney were identified as sulfamethazine, N4-acetylsulfamethazine, the N4-glucose conjugate of sulfamethazine, and N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide (desaminosulfamethazine). The major 14C-labeled compounds in the urine and feces were identified as sulfamethazine and N4-acetylsulfamethazine.

Renal and mammary excretion of sulfadimidine in buffaloes

The renal and mammary excretion of sulfadimidine was investigated in 8 lactating buffaloes after intravenous administration. The results showed that sulfadimidine was bound to the proteins in plasma (39--59 per cent) and milk (5.5 per cent). The renal handling of sulfadimidine was influenced by the variations in the urinary pH and the concentration of non-protein-bound drug. From the results it is concluded that glomerular filtration, back diffusion and active tubular secretion are involved in the renal handling of sulfadimidine in buffaloes. The results of mammary excretion showed that sulfadimidine is excreted into milk of buffaloes in concentration lower than in plasma. The ratio between the concentration of sulfadimidine in milk and plasma increases when the pH of milk increases. The results are consistant with the theory that drugs are excreted through the mammary gland by passive diffusion.

Acetylator phenotype in spontaneous SLE and rheumatoid arthritis

Acetylator phenotype was determined in 22 patients with spontaneous systemic lupus erythematosus and the proportion of 'slow' acetylators compared with that obtained in a group of patients with rheumatoid arthritis and a group of healthy controls. 73% of the SLE group were designated 'slow' compared with 72% of the rheumatoid group and 64% of the control group. These differences were not significant.

Mechanisms of nonlinear disposition kinetics of sulfamethazine

Five healthy male subjects received oral doses of 10 and 40 mg/kg of sulfamethazine (SMZ) approximately 14 days apart in a nonrandomized crossover study. Blood and urine samples were collected for at least 24 and 72 hr, respectively. All samples were assayed by the Bratton-Marshall procedure for SMZ and apparent N-acetylsulfamethazine (NSMZ). Recovery of total drug (SMZ + NSMZ) in urine was 88.9% following the low and 79.5% following the high dose. The low and high dose plasma concentration time curves were not readily superimposable (i.e., nonlinear kinetic behavior was observed). The data suggest that several mechanisms contribute to the nonlinearity. Specifically, a dose-dependent decrease in absorption rate displaced the plasma concentration-time curve to the right in some subjects, whereas apparent metabolic clearance (Clm) decreased with increasing dose (estimated assuming dose = amount of SMZ + NSMZ in urine to 72 hr) in all subjects (0.35 ml/min/kg for the low and 0.23 for the high dose). Still greater dose-dependent effects were found when apparent Clm of unbound drug was determined, since free fraction rose from 0.11 to 0.30 over the observed plasma concentration range. Renal clearance (ClR) of Smz appeared to be a complex function of time. In the low dose study it ranged from an average of 0.071 ml/min/kg at 2 hr to 0.146 ml/min/kg at 6 hr after drug. After the high dose comparable values were 0.083 and 0.128. Interindividual variability and pronounced nonlinear kinetics of SMZ after 40 mg/kg suggest that this dose is probably a poor choice for the determination of acetylator phenotype.

Estrogen-dependent differences in the acetylation of sulfadimidine in the rat

The influence of sex hormones on the acetylation of sulfadimidine was investigated in male and female rats, both intact and castrated. Sulfadimidine was administered intravenously in the dose of 40 mg/kg body weight, and unchanged and acetylated sulfadimidine (Ac-S) were then determined in urine and blood. It was found that the percentage of Ac-S was significantly higher in the urine of females than males. The concentration of sulfadimidine in blood was also higher in females than in males. While estrogenization raised the percentage of Ac-S in the urine of males and the concentration of unchanged sulfadimidine in blood, treatment with an androgen had no significant effect in females. The long-lasting stimulatory influence of estrogen in males and a normal percentage of Ac-S in gonadectomized females suggest an indirect action of estrogen. Possible mechanisms are discussed.

Disposition of sulfonamides in food-producing animals: pharmacokinetics of sulfamethazine in lambs

Previously reported plasma and urine concentrations of unchanged sulfamethazine and 3 metabolites following intravenous administration of sodium sulfamethazine to young ewe lamb were fitted to a linear pharmacokinetic model in which sulfamethazine itself obeyed 1-compartment phamacokinetics. The average rate constant for overall elimination of sulfamethazine was 0.096 +/- 0.023 hours-1, corresponding to a biological half-life of 7.2 +/- 1.7 hours. The results of residue analysis of 8 tissues obtained at slaughter showed that tissue and plasma concentrations and urine output of unchanged sulfamethazine fell parallel throughout the experiment. The results indicate that determination of the plasma concentration or urinary output of sulfamethazine can be substituted for tissue residue analysis to determine contamination of carcasses above specified tolerance limits.

Disposition of sulfonamides in food-producing animals: concentrations of sulfamethazine and its metabolites in plasma, urine, and tissues of lambs following intravenous administration

A sensitive, precise, and efficient analytical method for sulfamethazine in the liver, kidney, heart, skeletal muscle, and fat of lambs is reported. The method involves freezing cubed tissue in liquid nitrogen, powdering the frozen tissue in a liquid nitrogen-cooled blender, and extracting the tissue on a sodium sulfate column with chloroform:acetone. A thin-layer chromatographic procedure capable of separating and quantitating sulfamethazine and 3 metabolites (acetyl, hydroxylated, and polar conjugate(s) in lamb urine is also reported. Sulfamethazine was administered intravenously (107.25 mg/kg body weight) to 14 cross-bred ewe lambs. The concentration of sulfamethazine in plasma and tissues and sulfamethazine and its metabolites in urine were determined in samples collected at specific postdosing times. The concentration of sulfamethazine in plasma exceeded 5 mg/100 ml for 18 to 24 hours after drug administration. The excretion of diazotizable materials in the urine was essentially complete at the 60th hour after dosing. The drug was excreted in the urine as sulfamethazine, a hydroxylated metabolite, acetylsulfamethazine, and polar conjugate(s). Tissue concentrations of the drug were greatest in the kidney and less (in decreasing quantities) in liver, heart, skeletal muscle, body fat, and omental fat.

The relationship between the metabolism of procainamide and sulfamethazine

The metabolism of sulfamethazine (SMZ), which is acetylated by a binodally distributed enzyme, and procainamide (PA) was compared in 21 normal volunteers, each given a single oral dosted metabolites, N-acetyl-procainamide (NAPA) and Ac-SMZ, were measured. Subjects with less than 64% Ac-SMZ in the 0-8 hour collection were termed "slow" and those with more than 64% were termed "fast" SMZ acetylators. Slow SMZ acetylators had 9.8 to 43.8% (24.1 +/- 10.13) NAPA recovered, and fast SMZ acetylators, 22.0 to 42.6% (33.7 +/- 7.29) NAPA, P less than 0.01. In addition, the calculated half-life of PA metabolism for slow SMZ acetylators was 9.0 to 33.8 hours (18.4 +/- 8.82) and for fast SMZ acetylators was 8.1 to 14.4 hours (10.9 +/- 2.19), P less than 0.01. For four subjects, SMZ acetylation phenotype did not correlate with the half-life of SMZ or PA metabolism; and in two, SMZ acetylation phenotype and half-life of metabolism did not correlate with the same PA indices. Even though slow SMZ acetylators have less NAPA recovered than fast SMZ acetylators, it is not yet clear that procainamide is metabolized by a bimodally distributed enzyme as is sulfamethazine.

Polymorphic acetylation of sulphadimidine in normal and uraemic man

After oral administration of sulphadimidine (mean dose 3.33 g) to 21 volunteers it was possible to distinguish fast and slow acetylators by calculating the acetylated fraction (%acSDD) in a single serum sample obtained at any time between 1/2-24 h. There was a close correlation between %acSDD in serum and in urine collected from 0-8 h. Two groups of patients with chronic renal failure were studied. Four of the first 8 patients studied would have been designated as slow acetylators from their low %acSDD in 0-8 h urine, but as fast acetylators from their %acSDD in serum 6 h after drug administration. The next 18 patients were given a smaller dose of SDD (2 g) and they showed complete intra-individual correlation between %acSDD in 0-24 h urine and in a serum sample obtained at 24 h. The patients could be divided into 2 sub-groups on the basis of %acSDD in serum and urine, thus demonstrating the ability of this procedure to distinguish fast and slow acetylators, even in advanced chronic renal failure.

Blood DDS levels and acetylation rates of sulphadimidine in leprosy patients

The plasma DDS clearance rates and the acetylation rates of Sulphadimidine were studied in a group of 30 leprosy patients comprising of 17 non-responders and 13 responders to DDS treatment. No differences in the acetylator type or in the plasma DDS clearance were seen between the responders and non-responders. Acetylation rate did not bear any relation to the plasma clearance of DDS in the non-responders. The findings indicate that the resistance to DDS therapy in these patients is not related to any abnormal metabolic disposition of DDS.

High-pressure liquid chromatographic separation, identification, and determination of sulfa drugs and their metabolites in urine

A high-pressure liquid chromatographic method for the separation and quantitative determination of sulfamethazine, sulfathiazole, and their N4-acetylated metabolites on an amino-bonded reversed-phase column was developed. The method is suitable for the analysis of these compounds in pure solutions as well as in cattle urine. Retention times were reproducible. Injection volumes containing 0.2 mug of individual sulfonamides or their acetyl derivatives were successfully quantitated; coefficients of variation ranged from 0 to 0.073 for individual sulfonamides.

Determination of the acetylator phenotype using matrix isoniazid

The development of a simple method for classifying subjects as slow or rapid acetylators is reported. The method is based on determining the ratio of acetylisoniazid to acid-labile isoniazid in the urine 23-24 hours after an oral dose of a slow-release isoniazid formulation. The results obtained when this method was applied to phenotype over 200 East African tuberculosis patients are described. It is suggested that the method would be particularly suitable for classifying tuberculosis out-patients.