A new acyl derivative of sulfadimethoxine inhibits phagocyte oxidative burst and ameliorates inflammation in a mice model of zymosan-induced generalised inflammation

Chronic inflammation and oxidative stress play a pivotal role in the pathophysiology of most challenging illnesses, including cancer, Alzheimer's, cardiovascular and autoimmune diseases. The present study aimed to investigate the anti-inflammatory potential of a new sulfadimethoxine derivative N-(4-(N-(2,6-dimethoxypyrimidin-4-yl) sulfamoyl) phenyl) dodecanamide (MHH-II-32). The compound was characterised by applying 1H-, 13C-NMR, EI-MS and HRFAB-MS spectroscopic techniques. The compound inhibited zymosan-induced oxidative bursts from whole blood phagocytes and isolated polymorphonuclear cells with an IC50 value of (2.5 ± 0.4 and 3.4 ± 0.3 µg/mL), respectively. Furthermore, the inhibition of nitric oxide with an IC50 (3.6 ± 2.2 µg/mL) from lipopolysaccharide-induced J774.2 macrophages indicates its in vitro anti-inflammatory efficacy. The compound did not show toxicity towards normal fibroblast cells. The observational findings, gross anatomical analysis of visceral organs and serological tests revealed the non-toxicity of the compound at the highest tested intraperitoneal (IP) dose of 100 mg/kg in acute toxicological studies in Balb/c mice. The compound treatment (100 mg/kg) (SC) significantly (P < 0.001) downregulated the mRNA expression of inflammatory markers TNF-α, IL-1β, IL-2, IL-13, and NF-κB, which were elevated in zymosan-induced generalised inflammation (IP) in Balb/c mice while upregulated the expression of anti-inflammatory cytokine IL-10, which was reduced in zymosan-treated mice. No suppressive effect was observed at the dose of 25 mg/kg. Ibuprofen was taken as a standard drug. The results revealed that the new acyl derivative of sulfadimethoxine has an immunomodulatory effect against generalised inflammatory response with non-toxicity both in vitro and in vivo, and has therapeutic potential for various chronic inflammatory illnesses.

Fungi extracellular enzyme-containing microcapsules enhance degradation of sulfonamide antibiotics in mangrove sediments

Mangroves represent a special coastal vegetation along the coastlines of tropical and subtropical regions. Sulfonamide antibiotics (SAs) are the most commonly used antibiotics. The application of white-rot fungi extracellular enzyme-containing microcapsules (MC) for aerobic degradation of SAs in mangrove sediments was investigated in this study. Degradation of three SAs, sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamethazine (SMZ), was enhanced by adding MC to the sediments. The order of SA degradation in batch experiments was SMX > SDM > SMZ. Bioreactor experiments revealed that SA removal rates were higher with than without MC. The enhanced SA removal rates with MC persisted with three re-additions of SAs. Thirteen bacteria genera (Achromobacter, Acinetobacter, Alcaligenes, Aquamicrobium, Arthrobacter, Brevundimonas, Flavobacterium, Methylobacterium, Microbacterium, Oligotropha, Paracoccus, Pseudomonas, and Rhodococcus) were identified to be associated with SA degradation in mangrove sediments by combination of next-generation sequencing, bacterial strain isolation, and literature search results. Results of this study suggest that MC could be used for SA removal in mangrove sediments.

Recovery of Lemna minor after exposure to sulfadimethoxine irradiated and non-irradiated in a solar simulator

Sulfonamides are the second most widely used group of veterinary antibiotics which are often detected in the environment. They are eliminated from freshwaters mainly through photochemical degradation. The toxicity of sulfadimethoxine (SDM) was evaluated with the use of Lemna minor before and after 1- and 4-h irradiation in a SunTest CPS+ solar simulator. Eight endpoints consisting of: number and total area of fronds, fresh weight, chlorophylls a and b, carotenoids, activity of catalase and guaiacol peroxidase, and protein content were determined. The total frond area and chlorophyll b content were the most sensitive endpoints with EC50 of 478 and 554 μg  L^-1, respectively. The activity of guaiacol peroxidase and catalase increased at SDM concentrations higher than 125 and 500 μg  L^-1, respectively. The SDM photodegradation rate for first order kinetics and the half-life were 0.259 h^-1 and 2.67  h, respectively. The results show that the toxicity of irradiated solutions was caused by SDM only, and the photoproducts appeared to be either non-toxic or much less toxic to L. minor than the parent compound. To study the recovery potential of L. minor, after 7 days exposure in SDM solutions, the plants were transferred to fresh medium and incubated for the next 7 days. L. minor has the ability to regenerate, but a 7-day recovery phase is not sufficient for it to return to an optimal physiological state.

Degradation of sulfadimethoxine catalyzed by laccase with soybean meal extract as natural mediator: Mechanism and reaction pathway

Natural laccase-mediator systems have been well recognized as an eco-friendly and energy-saving approach in environmental remediation, whose further application is however limited by the high cost of natural mediators and relatively long treatment time span. This study evaluated the water extract of soybean meal, a low-cost compound system, in mediating the laccase catalyzed degradation of a model contaminant of emerging concern, sulfadimethoxine (SDM), and demonstrated it as a promising alternative mediator for soil and water remediation. Removal of 73.3% and 65.6% was achieved in 9 h using soybean meal extract (SBE) as the mediating system for laccase-catalyzed degradation of sulfadimethoxine at the concentration of 1 ppm and 10 ppm, respectively. Further degradation of sulfadimethoxine was observed with multiple SBE additions. Using SBE as mediator increased the 9-h removal of SDM at 1 ppm initial concentration by 52.9%, 49.4%, and 36.3% in comparison to the system mediated by 1-Hydroxybenzotriazole (HBT), p-Coumaric acid (COU) and 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), respectively. With the detection of stable coupling products formed with radical scavenger (5,5-Dimethyl-1-pyrroline N-oxide, DMPO), three phenolic compounds (vanillin, apocynin, and daidzein) in SBE were confirmed to serve as mediators for Trametes versicolor laccase. Reaction pathways were proposed based on the results of High Resolution Mass Spectrometry. SO2 excursion happened during SDM transformation, leading to elimination of antimicrobial activity. Therefore, as a natural, phenol rich, and affordable compound system, the future application of SBE in wastewater and soil remediation is worth exploring.

Bacterial communities associated with sulfonamide antibiotics degradation in sludge-amended soil

This study investigated the degradation of sulfonamide antibiotics (SAs) and microbial community changes in sludge-amended soil. In batch experiments, SA degradation was enhanced by addition of spent mushroom compost (SMC), SMC extract, and extract-containing microcapsule, with SMC showing higher SA degradation rate than the other additives in soil-sludge mixtures. In bioreactor experiments, the degradation of SAs in soil-sludge mixtures was in the order of sulfamethoxazole > sulfadimethoxine > sulfamethazine during four times of SA addition. SA removal was higher in soil-sludge mixtures than in soil alone. The bacterial composition differed in soil-sludge mixtures with and without SMC. In total, 44 differentially distributed bacterial genera were identified from different experimental settings and stages. Four bacterial genera, Acinetobacter, Alcaligenes, Brevundimonas, and Pseudomonas, were previously found involved in SA degradation, and 20 of the 44 bacterial genera were previously found in aromatic hydrocarbon degradation. Therefore, these bacteria have high potential to be SA degradation bacteria in this study.

Degradation of sulfonamides antibiotics in lake water and sediment

Degradation of three sulfonamides (SAs), namely sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadimethoxine (SDM) in surface water and sediments collected from Taihu Lake and Dianchi Lake, China was investigated in this study. The surface water (5-10 cm) was collected from the east region of Taihu Lake, China. Two sets of degradation experiments were conducted in 3-L glass bottles containing 2 L of fresh lake water and 100 μg/L of individual SAs aerated by bubbling air at a rate of approximately 1.2 L/min, one of which was sterilized by the addition of NaN3 (0.1%). Sediment samples were taken from Taihu Lake and Dianchi Lake, China. For the sediment experiment, 5 g of sediment were weighed into a 50-mL glass tube, with 10 mg/kg of individual SAs. Different experimental conditions including the sediment types, sterilization, light exposure, and redox condition were also considered in the experiments. The three SAs degraded in lake water with half-lives (t 1/2) of 10.5-12.9 days, and the half-lives increased significantly to 31.9-49.8 days in the sterilized water. SMZ and SDM were degraded by abiotic processes in Taihu and Dianchi sediments, and the different experimental conditions and sediments characteristics had no significant effect on their declines. SMX, however, was mainly transformed by facultative anaerobes in Taihu and Dianchi sediments under anaerobic conditions, and the degradation rate of SMX in non-sterile sediment (t 1/2 of 9.6-16.7 days) were higher than in sterilized sediment (t 1/2 of 18.7-135.9 days). Under abiotic conditions, degradation of SMX in Dianchi sediment was faster than in Taihu sediment, probably due to the higher organic matter content and inorganic photosensitizers concentrations in Dianchi sediment. High initial SAs concentration inhibited the SAs degradation, which was likely related to the inhibition of microorganism activities by high SAs levels in sediments. Results from this study could provide information on the persistence of commonly used sulfanomides antibiotics in lake environment.

Accumulation and effects of sulfadimethoxine in Salix fragilis L. plants: a preliminary study to phytoremediation purposes

The application of manure to fertilize arable lands is one of the major means through which veterinary sulfonamides (SAs) enter the environment. Little is known about the capacity of woody plants to phytoremediate this class of antibiotics. To this purpose we performed preliminary studies to evaluate Salix fragilis L. response to sulfadimethoxine (SDM) by investigating both its ability to absorb and tolerate doses of SDM found in fresh faeces of treated calves. Forty cuttings were exposed to either 0, 0.5, 1, or 2 mM of SDM for one month. Decreases in photosynthetic electron transport rate and net CO2 assimilation after 25 days for the higher SDM concentrations were noticed. Moreover, alterations in root morphology of treated plants were observed and further investigated through electron microscopy. However, collected data revealed high root accumulation potential. These preliminary results are promising as they demonstrate that Salix fragilis L. can both absorb and tolerate high concentrations of SAs.

Sorption and biodegradation of sulfonamide antibiotics by activated sludge: experimental assessment using batch data obtained under aerobic conditions

This study investigated the adsorption, desorption, and biodegradation characteristics of sulfonamide antibiotics in the presence of activated sludge with and without being subjected to NaN(3) biocide. Batch experiments were conducted and the relative contributions of adsorption and biodegradation to the observed removal of sulfonamide antibiotics were determined. Three sulfonamide antibiotics including sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamonomethoxine (SMM), which had been detected in the influent and the activated sludge of wastewater treatment plants (WWTP) in Taiwan, were selected for this study. Experimental results showed that the antibiotic compounds were removed via sorption and biodegradation by the activated sludge, though biodegradation was inhibited in the first 12 h possibly due to competitive inhibition of xenobiotic oxidation by readily biodegradable substances. The affinity of sulfonamides to sterilized sludge was in the order of SDM > SMM > SMX. The sulfonamides existed predominantly as anions at the study pH of 6.8, which resulted in a low level of adsorption to the activated sludge. The adsorption/desorption isotherms were of a linear form, as well described by the Freundlich isotherm with the n value approximating unity. The linear distribution coefficients (K(d)) were determined from batch equilibrium experiments with values of 28.6 ± 1.9, 55.7 ± 2.2, and 110.0 ± 4.6 mL/g for SMX, SMM, and SDM, respectively. SMX, SMM, and SDM desorb reversibly from the activated sludge leaving behind on the solids 0.9%, 1.6%, and 5.2% of the original sorption dose of 100 μg/L. The sorbed antibiotics can be introduced into the environment if no further treatments were employed to remove them from the biomass.

Sulfadimethoxine degradation kinetics in manure as affected by initial concentration, moisture, and temperature

Sulfadimethoxine is a widely used sulfonamide veterinary antibiotic and could be a source of agricultural contamination. Therefore, information is needed about its degradation kinetics in manure under aerobic conditions. Based on the analysis of first-order kinetics and the assumption that sulfadimethoxine availability for degradation in manure could be limiting, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterile manure was found to be much lower than in nonsterile manure, indicating that biodegradation was significant. In biologically active manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the activity of the degrading microorganisms was inhibited. Increasing moisture or temperature was found to increase sulfadimethoxine degradation in manure. Mixing manure containing high levels of sulfadimethoxine with manure containing lower levels may result in more rapid degradation, thus greatly diminishing sulfadimethoxine contamination in manure and significantly reducing sulfadimethoxine inputs into the environment. During treatment, keeping the manure moist and storing in a moderately warm place under aerobic conditions may also help to diminish sulfadimethoxine contamination.

Degradation kinetics of manure-derived sulfadimethoxine in amended soil

Spreading of contaminated manure into agricultural lands as fertilizer is one of the major routes through which veterinary antibiotics enter the environment. In this study, the degradation of manure-derived sulfadimethoxine, a widely used veterinary sulfonamide antibiotic, in manure-amended soil was investigated. A kinetic model, called the availability-adjusted first-order model based on the first-order kinetics and an assumption of the availability of target compound during the degradation process, was developed and was found to fit sulfadimethoxine degradation well. The effect of initial sulfadimethoxine concentration showed that the degradation rate constant increased with decreasing initial concentration, indicating that the bioactivity of the degrading microorganisms in manure-amended soil was sensitive to sulfadimethoxine concentration. Sulfadimethoxine degradation was accelerated with increasing manure content in amended soil. Degradation in nonamended soil was significantly slower than in manure-amended soil. This indicated that sulfadimethoxine may become more persistent once it reaches soil after leaching from manure and that storage of manure for a certain period before application is needed to diminish sulfadimethoxine contamination. Sulfadimethoxine degradation was effectively enhanced with increasing moisture of amended soil. No adverse effect was observed with manure storage on the degradation of manure-derived sulfadimethoxine in amended soil.

In vitro hepatobiotransformation of sulphadimethoxine in laying hens

The biotransformation of sulphadimethoxine (SDM) was estimated in liver post-mitochondrial supernatants (S-9) from laying hens. The pathway and activity for hen S-9 were compared with those for cow and pig S-9. The formation of the hydroxylation of SDM, 6-hydroxy SDM (6-OH-SDM), was found only with hen S-9. The N4-acetylating activity of SDM in hen S-9 was lower than in cow and pig S-9. All S-9 from the three species de-acetylated N4-acetyl SDM (N4-AcSDM). With respect to the hydroxylation and N4-acetylation rates in hen S-9, the values incubated at 41 degrees C were higher than those at 37 degrees C (P < 0.01).

The biotransformation of sulfadimethoxine, sulfadimidine, sulfamethoxazole, trimethoprim and aditoprim by primary cultures of pig hepatocytes

The in vitro biotransformation of three sulfonamides, trimethoprim and aditoprim, was studied using primary cultures of pig hepatocytes. Incubation of monolayer cultures with sulfadimethoxine (SDM), sulfamethoxazole (SMX) and 14C-sulfadimidine (SDD) resulted in the formation of the corresponding N4-acetylsulfonamide to different extents, depending upon the molecular structure of the drug. Addition of the acetylsulfonamides to the cells showed that these compounds were deacetylated, each to a different extent. A relatively low degree of acetylation (in the case of SDD) was paralleled by extensive deacetylation (i.e. AcSDD), whereas extensive acetylation (i.e. SMX) was in concert with minor deacetylation (i.e. AcSMX). The addition of bovine serum albumin to the medium resulted in a decrease in conversion of sulfonamides as well as acetylsulfonamides. The main metabolic pathway of 14C-trimethoprim (TMP) was O-demethylation with subsequent conjugation. Two hydroxy (demethyl) metabolites were formed, namely 3'- and 4'-demethyl trimethoprim, which were both glucuronidated while 3'-demethyl trimethoprim was also conjugated with sulphate. The capacity to form conjugates with either glucuronic acid or sulphate was at least as high as the capacity for O-demethylation since more than 90% of the metabolites were excreted as conjugates in the urine of pigs. Addition of 14C-aditoprim (ADP) to the hepatocytes led to the N-demethylation of ADP to mono-methyl-ADP and didesmethyl-ADP. During the incubation another three unknown ADP metabolites were formed. In contrast to TMP, no hydroxy metabolites or conjugated metabolites of aditoprim were formed. These in vitro results were in agreement with the in vivo biotransformation pattern of the studied sulfonamides and trimethoprim in pigs.

Metabolism of 14C-sulphadimethoxane in swine

1. 14C-sulphadimethoxine (4-amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzene-[U-14C]-sulphonamide; 14C-SDM) was given orally (60 mg/kg body weight) to eight swine (weight 27-32 kg). Urine and faeces were collected from 0 to 72 h after dosing and tissue samples were collected from animals exsanguinated at 12, 24, 48 and 72 h after dosing. The concentration of total 14C-labelled residues (14C-SDM equivalents) in tissues other than the gastrointestinal tract ranged from 99-1 ppm (plasma) to 13.8 ppm (adipose tissue) 12 h after dosing. Seventy-two hours after dosing tissue concentrations ranged from 5.4 ppm (plasma) to 0.5 ppm (skeletal muscle). The concentration in the large intestine was substantially higher (10.4 ppm) than in the stomach (2.8 ppm) and small intestine (1.4 ppm) 72 h after dosing. 2. Of the 14C, 77% was excreted in the urine from 0 to 72 h after dosing with 14C-SDM, mostly in the 0-24-h collection. Fifteen percent was excreted in the faeces from 0 to 72 h after dosing, with most of this occurring 36-72 h post-dosing. 3. 14C-SDM accounted for 24% (liver) to 66% (adipose tissue) and the N4-acetyl derivative of SDM (N4-Ac-SDM) accounted for 10% (skeletal muscle) to 35% (kidney) of the total 14C in the tissues 12 h after dosing. The N4-glucose conjugate of SDM (G-SDM) was a major 14C-labelled compound in skeletal muscle (21% of total) and liver (28%) but it was not detected in adipose tissue or kidney. The N4-glucuronic acid conjugate of SDM (GA-SDM) was a minor metabolite in kidney, but was not detected in other tissues collected 12 h after dosing. Desamino SDM was a minor metabolite in the kidney. A minor metabolite in plasma was identified as the sulphate ester of 3-hydroxysulphadimethoxine. 4. 14C-labelled fractions isolated from 0 to 6-h urine included N4-Ac-SDM (82%), SDM (3%) and GA-SDM (6%).

Oral bioavailability and disposition of sulphadimethoxine in lobster, Homarus americanus, following single and multiple dosing regimens

1. Single and multiple oral doses of sulphadimethoxine or sodium sulphadimethoxine were administered by gavage to lobster, and sequential samples of haemolymph were taken for analysis of parent sulphadimethoxine. Single doses of sodium sulphadimethoxine were given over a dose range of 14-70 mg/kg. Five 42-mg/kg doses of sulphadimethoxine on alternate days were administered for the multiple-dose studies. Some experiments were conducted with radiolabelled (35S or 14C) sulphadimethoxine, and the tissue distribution of radioactivity was determined at different killing times. 2. Pharmacokinetic parameters were obtained by fitting sulphadimethoxine concentrations in haemolymph to a one-compartment model. Oral bioavailability at the 42-mg/kg dose, calculated from the area under the haemolymph concentration-time curve (AUC) relative to the AUC from intravascular administration, was between 47 and 52% for single or multiple doses of the free drug. The bioavailability of sodium sulphadimethoxine was dose dependent, at 97% for the 14 mg/kg dose, and 25% for the 70-mg/kg dose. The low bioavailability at the high dose probably resulted from poor absorption due to the limited solubility of sulphadimethoxine at the low pH of the lobster gastrointestinal tract. 3. Sulphadimethoxine and several polar metabolites were excreted in lobster urine. Polar metabolites were also found in the hepatopancreas and haemolymph. At least 20% of the 42-mg/kg dose was metabolized. The major vertebrate metabolite of sulphadimethoxine, N-acetylsulphadimethoxine, was a very minor metabolite in lobster. The identities of the polar metabolites were not established. 4. Elimination of sulphadimethoxine residues from muscle to < 0.1 microgram sulphadimethoxine equivalent/g tissue required 40 days after a single dose, or 44 days after the last of multiple doses. Concentrations of sulphadimethoxine residues in all other tissues were always greater than muscle concentrations. Data showed that sulphadimethoxine residues were very persistent in lobster tissues.

Stability of sulfaquinoxaline, sulfadimethoxine, and their N4-acetyl derivatives in chicken tissues during frozen storage

The N4-acetyl derivatives of sulfaquinoxaline and sulfadimethoxine were stable in fortified chicken liver and thigh muscle tissues during frozen storage for 1 year at -20 and -70 degrees C. In contrast, the parent compounds depleted approximately 35% in liver tissues at -20 degrees C. The transformation of the depleted sulfa drugs to their N4-glucopyranosyl derivatives was negligible, suggesting that products other than glucosides resulted during the storage period.

Development of a screening method for five sulfonamides in salmon muscle tissue using thin-layer chromatography

A thin-layer chromatographic (TLC) method was developed for the analysis of five sulfonamides [sulfadiazine (SDZ), sulfamerazine (SMRZ), sulfamethazine (SMTZ), sulfadimethoxine (SDMX) and sulfapyridine (SP)] in salmon muscle tissue. "Matrix solid-phase dispersion" was employed whereby the tissue sample was ground with C18-derivatized silica gel. This material was packed into a column and washed with 10% toluene in hexane (discarded) followed by dichloromethane which was evaporated. The residue was chromatographed on a high-performance TLC plate using ethyl acetate-n-butanol-methanol-aqueous ammonia (35:45:15:2, v/v). Sulfonamides were detected after spraying the plate with a solution of fluorescamine. Method parameters were determined by analyzing spiked salmon muscle tissue samples. The method detection limits at the 99% confidence level were 0.11, 0.44, 0.07, 0.13 and 0.13 ppm for SDZ, SMRZ, SMTZ, SDMX and SP, respectively. The lowest-detectable levels were approximately 0.04 ppm for SDZ, SMTZ, SDMX and SP, and 0.10 ppm for SMRZ. The average recoveries of analyses were 61, 63, 60, 63 and 57% for SDZ, SMRZ, SMTZ, SDMX and SP, respectively, and were found to be analyst-dependent. The method was found to give linear detector responses for all analytes over spiking levels ranging from 0 to 2 ppm.

High-performance liquid chromatographic analysis of Romet-30 in salmon following administration of medicated feed

A sensitive and selective high-performance liquid chromatographic assay was developed for the simultaneous quantitation of sulphadimethoxine (SDM) and ormetoprim (OMP) in chinook salmon muscle tissue. SDM and OMP were extracted from tissue samples using a solid-phase extraction technique. Resolution of both drugs was accomplished using an Ultrasphere ion-pair column (250 x 4.6 mm I.D.) and a mobile phase of acetonitrile-methanol-0.1 M phosphate buffer, pH 4 (17:10:73) with ultraviolet detection at 280 nm. The calibration curve in salmon muscle tissue was linear over the concentration range 0.2-20 ppm for both SDM (r2 = 0.9974) and OMP (r2 = 0.9956). The minimum detectable quantity of SDM and OMP in salmon muscle tissue was 0.2 ppm at a signal-to-noise ratio of 5:1. An in vivo feeding experiment was undertaken where chinook salmon were administered Romet-30-medicated feed for a 10-day period, followed by a 42-day wash-out period. The rate of tissue uptake and decline of SDM and OMP was shown to differ.

Pharmacokinetics, N1-glucuronidation and N4-acetylation of sulfadimethoxine in man

Sulfadimethoxine is metabolized by O-dealkylation, N4-acetylation and N1-glucuronidation. In man, only N1-glucuronidation and N4-acetylation takes place, leading to the final double conjugate N4-acetylsulfadimethoxine-N1-glucuronide. The N1-glucuronides are directly measured by high pressure liquid chromatography. When N4-acetylsulfadimethoxine is administered as parent drug, 30% of the dose is N1-glucuronidated and excreted. Fast acetylators show a shorter half-life for sulfadimethoxine than slow acetylators (27.8 +/- 4.2 h versus 36.3 +/- 5.4 h; P = 0.013), similarly the half-life of the N4-acetyl conjugate is also shorter in fast acetylators (41.3 +/- 5.2 h versus 53.5 +/- 8.5 h, P = 0.036). No measurable plasma concentrations of the N1-glucuronides from sulfadimethoxine are found in plasma. N1-glucuronidation results in a 75% decrease in protein binding of sulfadimethoxine. N4-acetylsulfadimethoxine and its N1-glucuronide showed the same high protein binding of 99%. Approximately 50-60% of the oral dose of sulfadimethoxine is excreted in the urine, leaving 40-50% for excretion into bile and faeces.

The role of plasma protein binding on the metabolism and renal excretion of sulphadimethoxine and its metabolite N4-acetylsulphadimethoxine in pigs

The effects of plasma protein binding on the elimination of sulphadimethoxine (SDM) were examined after intravenous administration of 6.25, 12.5, 25, 50, 100 and 150 mg/kg to pigs. At an early stage of the experiment, the animals were anaesthetised by inhalation of enflurane to obtain a more exact relationship between plasma concentration and the renal excretion. SDM and its acetylated conjugate, N4-acetylsulphadimethoxine (N4-SDM) were detected in plasma and urine of all animals, and the recovery of the doses was almost complete in two animals with negligible renal excretion of SDM. The percentages of plasma protein binding of SDM and N4-SDM were almost similar, and ranged from 30 to 95%, depending on the plasma concentration. The metabolic clearance of SDM by acetylation increased when the plasma protein binding decreased. These results suggested that the main elimination route of SDM in pigs is acetylation, and that the plasma protein binding can have a large effect on the elimination of SDM in pigs. The effect of plasma protein binding on the renal clearance of SDM was not so evident, because urine pH had a much greater effect on it. The deacetylation of N4-SDM was detected after 25 mg/kg intravenous administration of N4-SDM, which suggests that the metabolic clearance of SDM is part of an acetylation-deacetylation equilibrium. Saturation of the active tubular reabsorption of SDM and of the active tubular secretion of N4-SDM was also suggested after higher doses of SDM.

High-performance liquid chromatography of sulphadimethoxine and its N1-glucuronide, N4-acetyl and N4-acetyl-N1-glucuronide metabolites in human plasma and urine

Sulphadimethoxine is metabolized in humans by N1-glucuronidation and by N4-acetylation. Sulphadimethoxine-N1-glucuronide can be measured by the direct high-performance liquid chromatographic analysis and without enzymic deglucuronidation. The N1-glucuronide can be measured by an isocratic as well as by a gradient mobile phase. The group contribution of the N1-glucuronide moiety to the capacity factor is a reduction of 0.24 in the isocratic system and 0.55 in the gradient system. N4-Acetylation increases the capacity factor by a factor 1.4 in the isocratic system and by 1.06 in the gradient system.

[Displacing effect of serum protein binding on intestinal absorption of sulfadimethoxine]

The displacing effect of serum protein binding on the intestinal absorption of sulfadimethoxine (SDM) in rabbits was examined by using N4-acetylsulfadimethoxine (N4-AcSDM), a major metabolite of SDM, as a displacing drug. N4-AcSDM markedly decreased the in vitro serum protein binding of SDM, while many drugs including phenylbutazone and salicylic acid did not display such a marked decreasing-effect. The intravenous administration of N4-AcSDM clearly decreased the in situ intestinal absorption of SDM. As expected, the intravenously administered N4-AcSDM enhanced the serum concentration of unbound SDM in the common jejunal vein. However, the intravenously administered N4-AcSDM caused no change in the transfer of SDM across the intestinal membrane. These results indicate that the displacement of serum protein binding can become one of factors decreasing the intestinal absorption of SDM.

Sulfadimethoxine-bucolome interaction in rabbits: role of N4-acetylsulfadimethoxine, a major metabolite of sulfadimethoxine

The role of N4-acetylsulfadimethoxine (N4-AcSDM), a major metabolite of sulfadimethoxine (SDM), in protein binding and pharmacokinetic interactions between SDM and bucolome (BCP) was investigated in rabbits. When SDM and BCP were intravenously co-administered, BCP indirectly reduced the serum protein binding of SDM by causing a marked increase of N4-AcSDM concentration in serum, and significantly increased the steady-state volume of distribution (Vss) and total body clearance (C1tot) of SDM. In addition, the co-administration of N4-AcSDM was found to increase Vss and C1tot of SDM. These results lead us to conclude that N4-AcSDM plays an important role in protein binding and pharmacokinetic interactions between SDM and BCP in rabbits. Several investigations have demonstrated that a metabolite plays an important role in drug-drug interaction. For example, Sellers et al. (1) reported that when warfarin and chloral hydrate are co-administered, a major metabolite of chloral hydrate, trichloroacetic acid, reduces the plasma protein binding of warfarin and enhances its anti-coagulant activity. Our previous paper (2) showed that probenecid indirectly reduces the plasma protein binding of sulfadimethoxine (SDM) by causing a marked increase in the plasma concentration of N4-acetylsulfadimethoxine (N4-AcSDM), which is a major metabolite of SDM (3) and strongly displaces SDM from its plasma protein binding sites (2). However, as yet the role of this metabolite in drug-drug interaction has not been fully examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Species-dependent glucuronidation of drugs by immobilized rabbit, rhesus monkey, and human UDP-glucuronyltransferases

The utility of immobilized microsomal enzymes from rabbit liver for the synthesis of a variety of conjugated drug metabolites has been demonstrated in our laboratory. Here, this capability is extended to microsomal preparations from monkey and human liver. A comparative study of glucuronidation of various substrates was carried out using immobilized uridine-5'-diphosphoglucuronyltransferase from rabbit, rhesus monkey, and human liver. The three drugs used for the study (sulfadimethoxine, oxazepam, and cyproheptadine) were chosen on the basis of their previously reported in vivo species differences in glucuronidation. Aglycons were incubated with UDP-glucuronic acid in the presence of immobilized UDP-glucuronyl-transferase at pH 7.4 for 16 hr at 37 degrees C. Glucuronide products were purified by high performance liquid chromatography and further characterized by thin layer chromatography and mass spectometry. Species-dependent glucuronidation was observed in all three cases. Differences in the in vitro product formation paralleled in vivo species differences for the three drugs studied. The same glucuronides were produced by immobilized human liver microsomes as have been found to be formed in vivo from the three drugs studied.

Ormetoprim-sulfadimethoxine in cattle: pharmacokinetics, bioavailability, distribution to the tears, and in vitro activity against Moraxella bovis

The pharmacokinetics, bioavailability, and distribution to the tears of ormetoprim (OMP; 5.5 mg/kg of body weight) and sulfadimethoxine (SDM; 27.5 mg/kg of body weight) were determined following IV or oral administration to 6 Holstein steers. After IV administration, the disposition kinetics of both drugs were best described by a 2-compartment open model. Sulfadimethoxine had a moderately rapid distribution phase, followed by a slower elimination phase, with a mean half-life (t 1/2) of 7.91 hours. The mean volume of distribution of SDM was 185 ml/kg, and the mean body clearance was 0.28 ml/min X kg. The concentration of SDM in tears was lower than the corresponding plasma concentration, and the elimination of SDM from tears (t 1/2 = 3.02 hours) was significantly faster than its elimination from plasma (t 1/2 = 7.91 hours). The disposition of OMP administered IV was characterized by a rapid distribution phase, followed by a rapid elimination phase (t 1/2 = 1.37 hours). The high values of the mean volume of distribution (1,450 ml/kg) and mean rate of body clearance (13.71 ml/min X kg) indicated that OMP was widely distributed in the body and was rapidly cleared from the body. Ormetoprim concentrations in tears exceeded corresponding plasma concentrations, and the elimination of OMP from tears was significantly slower (t 1/2 = 1.91 hours) than from plasma (t 1/2 = 1.37 hours). After oral administration of an OMP-SDM combination in bolus form, the absorption of SDM was slow (absorption t 1/2 = 3.32 hours), but complete.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of phenylbutazone on serum protein binding of sulfadimethoxine in different animal species

The effect of phenylbutazone (PBZ) on the in vivo serum protein binding of sulfadimethoxine (SDM) was examined in dogs, rabbits and rats. In dogs, PBZ itself was found to displace SDM from its protein binding sites. In rabbits, PBZ indirectly reduced the in vivo serum protein binding of SDM through the interaction of PBZ with N4-acetylsulfadimethoxine (N4-AcSDM), a major metabolite of SDM. In rats, however, PBZ had no effect on the in vivo serum protein binding of SDM. It is noteworthy that species differences were observed in the effect of PBZ on the in vivo serum protein binding of SDM.

Effect of bile acids on the binding of drugs and dyes to human albumin

Chenodeoxycholic, cholic, deoxycholic and taurodeoxycholic acids were found to inhibit the binding of 2-(4'-hydroxybenzeneazo)benzoic acid, methyl orange, sulphadimethoxine and warfarin to human albumin. In addition, glycodeoxycholic acid inhibited the binding of sulphadimethoxine and warfarin. In contrast, these bile acids did not inhibit the binding of phenylbutazone. The extent of displacement was in the rank order of: dihydroxy acids (chenodeoxycholic and deoxycholic) greater than trihydroxy acid (cholic) greater than conjugates (glycodeoxycholic and taurodeoxycholic). Thus the introduction of polar groups into the steroid nucleus of bile acids reduces their effectiveness as binding inhibitors. Displacement was usually accompanied by a decrease in the apparent association constant which suggests that the mechanism of displacement may be competitive.

Effect of synthetic surfactants on drug absorption in the presence of a physiologic surfactant, sodium taurocholate, in rats

The effect of synthetic surfactants and their binary mixture with a physiologic one, sodium taurocholate (STC), on the intestinal absorption of drugs was examined in rats by using the in situ recirculation technique. Synthetic surfactants investigated in this study were nonionic polysorbate 80 (PS-80), cationic cetyltrimethylammonium bromide (CTAB), and anionic sodium lauryl sulfate (SLS). The surfactant action on the mucosal membrane seemed to be the same magnitude as the stronger one of the two components, except in the case of CTAB, as estimated by the enhancement effect on sulfaguanidine absorption. The action of CTAB was increased in the presence of STC. The action of surfactants in the aqueous solution, an intraluminal action, was examined by using quinine as a model drug. The micellar interaction of the drug with an ionic surfactant, CTAB or SLS, was reduced by the addition of STC, whereas, that with a nonionic surfactant, PS-80, was increased as estimated by a dynamic dialysis technique. The inhibitory effect on quinine absorption was approximately proportional to the degree of the micellar complex formation. Two other model drugs, imipramine and sulfadimethoxine, were further examined and the possible mechanisms of these effects were discussed.

Differences in effects on drug absorption between dihydroxy and trihydroxy bile salts

The effect of a dihydroxy bile salt, sodium taurodeoxycholate (STDC), on drug absorption from rat small intestine was investigated in comparison with that of trihydroxy one, sodium cholate (STC). The enhancement or inhibitory effects on the absorption of various model drugs by STDC bore similar tendency to those by STC, and the magnitude was greater than the latter. The absorption of sulfaguanidine was enhanced by STDC, which solubilized the phospholipids from the mucosal barrier membrane in addition to the STC-like, or ethylenediaminetetraacetate-like action. STDC inhibited the absorption of sulfadimethoxine contrary to the insignificant effect by STC. The direct action of STDC on the mucosal membrane reduced the absorption in addition to the physicochemical action, such as micellar complex formation. Quinine absorption was inhibited in the presence of STDC, which can be explained by the micellar complex formation. Possible mechanisms of the differences in the effect of STDC and STC were discussed in relation to their micellar properties.

[Distribution of sulfanilamides and penicillins in the blood and organs of rats after their combined administration]

The use of benzylpenicillin and ampicillin in combination with sulfalen or sulfadimethoxine increased the levels of the penicillins and sulfalen in some organs and tissues of rats. This was accompanied by a rise in the concentration gradients of the drugs. It is concluded that the combined use of the penicillins and sulfanilamides determines their increased penetration from the blood into other organs and tissues of the host.

[Pharmacokinetics of sulfalene and sulfamethoxine after combined administration with benzylpenicillin and ampicillin]

The binding of sulfadimethoxine by serum proteins of rabbits did not change in the presence of benzylpenicillin and ampicillin, while the binding of sulfalen increased. The 1.2-2-fold decrease in the proportion of sulfalen not bound by blood proteins was accompanied by its acetylation in rabbits. This in its turn resulted in a decreased rate of the drug elimination. The penicillins did not change the kinetics of sulfadimethoxine in rabbits. When the dose of sulfadimethoxine was increased 2 times, the rate of its elimination in rabbits increased, which is likely to be due to increased acetylation of the drug. This may be associated with the increased level of the free sulfadimethoxine fraction in the blood because of the drug lower binding by serum proteins. When the dose of sulfalen was increased 2 times, its kinetics in rabbits did not change.

[Characteristics of the distribution of long-acting sulfanilamides in purulent pyelonephritis in rats]

Distribution of sulfalen, sulfadimethoxine and sulfamethoxypyridazine in the blood and organs of rats and binding of the drugs to the blood serum proteins of the animals with experimental P. aeruginosa pyelonephritis were studied. It was shown that in rats with P. aeruginosa pyelonephritis the levels of long-acting sulfanilamides in the blood and organs were lower, while the levels of their penetration through the histohematic barriers were higher, which was partially due to the decreased binding of sulfanilamides to blood proteins.

[Sulfadimethoxine pharmacokinetics in mechanical jaundice and cholangitis]

The rate of sulfadimethoxine excretion from blood in patients with mechanical jaundice and cholangitis is the same as that in healthy persons. The renal excretion of the drug in such patients does not undergo any significant changes either. However, excretion of sulfadimethoxine with bile is impaired and the level of suppression of renal excretory function is proportional to the jaundice period. After decompression of the bile ducts renal excretory function in patients with mechanical jaundice is recovered.

Disposition of sulfadimethoxine in swine: inclusion of protein binding factors in a pharmacokinetic model

Sulfadimethoxine was administered intravenously and orally to five swine. More than 75% of the dose was excreted into urine as the acetyl metabolite with 4-6% excreted unchanged. Plasma and urine data were not consistent when a linear pharmacokinetic model was used to describe the data. Sulfadimethoxine has a high affinity for plasma protein, and the data were subsequently fitted to a nonlinear model, which included saturable protein binding. The choice of a nonlinear model was further supported by a minimum value for the Akaike information criteria. The protein binding constant obtained was 2.8 X 10(4) M-1 and the total protein binding site concentration in plasma was 4.6 X 10(-4) M. Both values are comparable with in vitro data. This result suggests that the nonlinear model involving protein binding can be successfully applied to pharmacokinetic data. The apparent biological half-life of sulfadimethoxine (free and bound) in plasma was 14 hr; however, the half-life of elimination of free drug was 1.25 hr. Following oral administration, all of the dose was absorbed with an apparent absorption half-life of 2.9 hr.

[Sulfadimethoxine pharmacokinetics in chronic nephritis with nephrotic syndrome]

Sulfadimethoxine excreted more rapidly in patients with chronic nephritis and the nephrotic syndrome than in subjects of the control group. Increased elimination of sulfadimethoxine from the blood of the persons with the kidney diseases was due to decreased reabsorption of the drug in the kidney tubules and increased rates of the drug biotransformation because of decreased binding by the blood serum proteins.

Pharmacokinetic study of sulfadimethoxine depletion in suckling and growing pigs

Sulfadimethoxine was administered (IV) to suckling pigs (1 to 2 weeks old) and to growing pigs (11 to 12 weeks old) at a dosage of 55 mg/kg of body weight (single dose). Blood samples were collected over a 48-hour period, and the animals euthanatized were used for measurements of plasma and tissue concentrations of the drug. The blood data were described, using a one-compartment pharmacokinetic model. The blood concentration curves for the two groups of pigs had a consistent depletion pattern with greater than therapeutic concentrations (50 micrograms/ml) of the drug persisting through 12 hours after the drug was given. Sulfonamide blood concentrations were 4 and 11 times that of the method sensitivities in the older (growing) and younger (suckling) pigs, respectively, at 48 hours after treatment. In four of the five pharmacokinetic variables studied, a significantly higher (P less than 0.01) degree of efficiency was observed in the ability of the older pigs to eliminate the drug than in the younger pigs.

Dextran induced hypoalbuminaemia as a model for the study of influences of protein binding on the pharmacokinetics of drugs

A model for examination of the effect of hypoalbuminaemia on drug pharmacokinetics in laboratory animal is described. The model has been used to investigate the effect of protein binding on the kinetics of sulphadimethoxine in rabbits. A greater volume of distribution of sulphadimethoxine is shown in the dextran induced hypoalbuminaemic rabbits in comparison with control animals. It is concluded that the suggested model is convenient for investigation of the influences of protein binding on drug pharmacokinetics.

[The effect of phenobarbital on the acetylation of sulfapyridazine and formation of sulfadimethoxine glucronide in man]

In the urine of 20 normal male students-volunteers aged 20 to 30 the percentage of acetylated sulphapyridazine and sulphadimetoxin was measudred 12 hours of taking by them 1.0 g of sulphanilamide. Takinpreliminarily phenobarbital (0.1 g before going to bed for 2 days) did not have any effect on the percentage of acetylated sulphapyridazine in the urine of the examined, nor did it affect the level of the free compound. Phenorbarbital was found to significantly raise the level of sulphadimetoxin from 84.3 up to 88.1 per cent in the urine, the amount of free sulphadimetoxine then declining. In experiments on isolated lenghts of the small intestine of the rat turned inside out it was shown that a coursewise introduction of phenobarbital (25 mg/kg for 5 days) did have any effect on the acetylation of sulphapyridazine.

Pharmacokinetics of sulfadimethoxine in cats

Pharmacokinetic parameters which describe distribution and elimination of sulfadimethoxine were determined in cats. Following intravenous administration of a single dose (55 mg/kg), disposition of the drug was described in terms of the biexponential expression: Cp = Ae-alphat + Be-betat. Based on total (free and bound) sulfonamide levels in the plasma, pseudodistribution equilibrium was slowly attained and the half-time of elimination (half-life) was 10.16 h +/- 2.50 (S.D., n = 6). Body clearance, which is the sum of all clearance processes, was 18.8 +/- 4.6 ml kg-1 h-1. Plasma protein binding, measured by equilibrium dialysis at sulfonamide concentration of 50 microgram/ml, was extensive (87.5% +/- 6.3, n =10). Computer-generated curves for an animal representative of the group, based on individual rate constants associated with the two-compartment open model, showed that 12% and 5% of the dose were present in the central and peripheral compartments, respectively, 24 h after administering the drug. A satisfactory dosage regimen might consist of a priming dose (55 mg/kg) and maintenance dosage (27.5 mg/kg at 24 h dosage intervals). Predicted plasma sulfadimethoxine concentrations would oscillate between 125 and 25 microgram/ml during the steady state. Influence of bacterial disease and febrile states on predicted levels remains to be verified experimentally.

Kinetics of drug-drug interactions in sheep: tolbutamide and sulfadimethoxine

The interaction between sulfadimethoxine and tolbutamide in sheep involving displacement from protein binding sites was investigated quantitatively. A 52% increase in the unbound plasma concentration of tolbutamide was observed in vitro at 37 degrees after the addition of sulfadimethoxine (100 microgram/ml) to sheep plasma containing tolbutamide (50 microgram/ml). Transient changes in tolbutamide's unbound and total plasma concentrations were noted after acute intravenous administration of sulfadimethoxine to sheep receiving a constant intravenous infusion of tolbutamide. These observations were consistent with displacement of tolbutamide from plasma and tissue binding sites and redistribution of the displaced tolbutamide into body water spaces. The steady state of both agents featured little change in the total plasma tolbutamide concentration, a 150% increase in the unbound plasma tolbutamide concentration, and an inhibition of tolbutamide oxidation by sulfadimethoxine. A model is presented and mathematical relationships are derived that permit a quantitation of the interaction and that indicate the sulfadimethoxine's constant of metabolic inhibition (K1) for tolbutamide metabolism is 65 microgram/ml.