Isolation, identification and determination of sulfamethoxazole and its known metabolites in human plasma and urine by high-performance liquid chromatography

Phytoremediation of diclofenac and sulfamethoxazole in Arabidopsis thaliana cells and seedlings

Diclofenac (DLF), a widely recognized non-steroidal anti-inflammatory drug (NSAID), and sulfamethoxazole (SMX), a broad-spectrum sulfonamide antibiotic, are commonly prescribed medications that have raised concerns as significant contributors to pharmaceutical pollution in natural ecosystems despite their clinical effectiveness. This study investigates the potential phytoremediation pathways for these two drugs in plant systems by tracking and quantifying the fate of the parent compounds and their metabolites in Arabidopsis thaliana using cell and seedling cultures. Results indicated significant differences in the dissipation of DLF according to the treatment and time interaction within the cell cultures. Viable plant cells showed complete dissipation of DLF from an initial concentration of 2758 ng/mL in 96 h, whereas non-viable cells and blank solutions remained stable. The dissipation of SMX was comparable across viable, non-viable, and blanks, showing a minor decrease from 842 to 799 ng/mL over 120 h following the treatment of viable cells. DLF metabolites including 4'-hydroxy-diclofenac, 5-hydroxy-diclofenac, acyl-glutamatyl-diclofenac, 1-(2,6-dichlorophenyl)-5-hydroxy-2-indolinone, 5-sulfooxy-diclofenac, 5-glucopyranosyloxy-diclofenac, 1-(2,6-dichloro-4-hydroxyphenyl)-2-indolinone, and 4'-glucopyranosyloxy-diclofenac were recognized, likely formed through acylation, glutamyl conjugation, hydroxylation, dehydration, cyclization, sulfonation, and glucosidation. While for SMX, metabolites including sulfamethoxazole-glucuronide, nitroso-sulfamethoxazole, N4-acetylsulfamethoxazole, and N4-acetyl-5-OH-sulfamethoxazole were identified, potentially produced through glucuronidation, nitrosation, acetylation, and hydroxylation. Phase I metabolite concentrations of DLF and SMX peaked earlier than those of phase II metabolites. Hydroponic A. thaliana demonstrated comparable efficiencies in the phytoremediation of DLF and SMX, with concentrations varying from 1 mg/L to 10 mg/L. Detectable levels of both parent compounds and their metabolites confirmed successful absorption and metabolism within the plant system. This study provides valuable insights into the potential of phytoremediation as a sustainable approach for reducing the environmental toxicity of DLF and SMX and suggests comparable metabolic efficiency. These findings contribute to the growing body of knowledge on phytoremediation and its application in addressing pollution from pharmaceuticals and personal care products.

Assessment of sulfamethoxazole toxicity to marine mussels (Mytilus galloprovincialis): Combine p38-MAPK signaling pathway modulation with histopathological alterations

Sulfamethoxazole (SMX), is a ubiquitous antibiotic in the aquatic environment and received concerns on its health hazards, especially its sub-lethal effects on non-target organisms which were remained largely unknown. In the present study, in order to investigate SMX induced tissue damages and reveal underlying mechanisms, marine mussels, Mytilus galloprovincialis were challenged to SMX series (0.5, 50 and 500 μg/L) for six-days followed by six-day-recovery. Comprehensive histopathological alteration (including qualitative, semi-quantitative and quantitative indices), together with transcriptional and (post-) translational responses of key factors (p38, NFκB and p53) in the p38-MAPK signaling pathway were analyzed in gills and digestive glands. Tissue-specific responses were clearly investigated with gills showing more prompt responses and digestive glands showing higher tolerance to SMX. The histopathology showed that SMX triggered inflammatory damages in both tissues and quantitative analysis revealed more significant responses, suggesting its potential as a valuable health indicator. SMX activated expressions of p38, NFκB and p53 at transcriptional and (post-) translational levels, especially after exposed to low level SMX, evidenced by p38 coupled with NFκB/p53 regulation on immunity defense in mussels. Less induction of targeted molecules under severe SMX exposure indicated such signaling transduction may not be efficient enough and can result in inflammatory damages. Taken together, this study expanded the understanding of aquatic SMX induced health risk in marine mussels and the underlying regulation mechanism through p38 signaling transduction.

Metabolic Disposition and Elimination of Tritum-Labeled Sulfamethoxazole in Pigs, Chickens and Rats

Sulfamethoxazole (SMZ), as a sulfa antibiotic, is often used in the treatment of various infectious diseases in animal husbandry. At present, SMZ still has many unresolved problems in the material balance, metabolic pathways, and residual target tissues in food animals. Therefore, in order to solve these problems, the metabolism, distribution, and elimination of SMZ is investigated in pigs, chickens, and rats by radioactive tracing methods, and the residue marker and target tissue of SMZ in food animals were determined, providing a reliable basis for food safety. After a single administration of [³H]-SMZ (rats and pigs by intramuscular injection and chickens by oral gavage), the total radioactivity was rapidly excreted, with more than 93% of the dose excreted within 14 days in the three species. Pigs and rats had more than 75% of the administered volume recovered by urine. After 7 days of continuous administration, within the first 6 h, radioactivity was found in almost all tissues. The highest radioactivity and longest persistence in pigs was in the liver, while in chickens it was in the liver and kidneys, most of which was removed within 14 days. A total of six, three and three metabolites were found in chickens, rats and pigs, respectively. N₄-acetyl-sulfamethoxazole (S1) was the main metabolite of SMZ in rats, pigs and chickens. The radioactive substance with the longest elimination half-life is sulfamethoxazole (S0), so S0 was suggested to be the marker residue in pigs and chickens.

A kinetic study of the photolysis of sulfamethoxazole with special emphasis on the photoisomer

Abstract

The previously not studied photochemical degradation of sulfamethoxazole (SMX) to the isomer of SMX (ISO) was measured via a polychromatic (Xe) and a monochromatic (Hg) light source and accompanied by quantum chemical DFT calculations. In addition to the $$\mathrm{p}K_\mathrm{a} = \;7.0 \pm 0.1$$ p K a = 7.0 ± 0.1 of ISO, tautomer-dependent properties such as the $$K_\mathrm{OW}$$ K OW were measured and theoretically confirmed by DFT. The kinetics in solutions below and above the $$\mathrm{p}K_\mathrm{a} = 5.6$$ p K a = 5.6 of SMX were studied for the available and quantifiable products SMX, ISO, 3-amino-5-methylisoxazole (AMI), 2-amino-5-methyloxazole (AMO), and sulfanilic acid (SUA). The quantum yields of the neutral ($$\Phi _\mathrm{N}$$ Φ N ) and anionic $$\Phi _\mathrm{A}$$ Φ A ) forms of SMX ($$\Phi _\mathrm{A} = 0.03 \pm 0.001$$ Φ A = 0.03 ± 0.001 , $$\Phi _\mathrm{N} = 0.15 \pm 0.01$$ Φ N = 0.15 ± 0.01 ) and ISO ($$\Phi _\mathrm{A} = 0.05 \pm 0.01$$ Φ A = 0.05 ± 0.01 and $$\Phi _\mathrm{N} = 0.06 \pm 0.02$$ Φ N = 0.06 ± 0.02 ) were found to be wavelength-independent. In a competitive reaction to the formation of ISO from SMX, the degradation product TP271 is formed. Various proposed structures for TP271 described in the literature have been studied quantum mechanically and can be excluded for thermodynamic reasons. In real samples in a northern German surface water in summer 2021 mean concentrations of SMX were found in the range of 120 ng/L. In agreement with the pH-dependent yields, concentrations of ISO were low in the range of 8 ng/L.

Graphical abstract

Fate of Sulfonamides and Tetracyclines in Meat during Pan Cooking: Focus on the Thermodegradation of Sulfamethoxazole

Although antimicrobials are generally found in trace amounts in meat, the human health risk they bear cannot be ignored. With the ultimate aim of making a better assessment of consumer exposure, this study explored the effects of pan cooking on sulfonamides and tetracyclines in meat. Screening of these antimicrobials in cooked meat was first performed by the European Union Reference Laboratory on the basis of HPLC-MS/MS analyses. A proof of concept approach using radiolabeling was then carried out on the most cooking-sensitive antimicrobial-sulfamethoxazole-to assess if a thermal degradation could explain the observed cooking losses. Degradation products were detected thanks to separation by HPLC and monitoring by online radioactivity detection. HPLC-Orbitrap HRMS analyses completed by 1D and 2D NMR experiments allowed the structural characterization of these degradation compounds. This study revealed that cooking could induce significant antimicrobial losses of up to 45% for sulfamethoxazole. Six potential degradation products of 14C-sulfamethoxazole were detected in cooked meat, and a thermal degradation pattern was proposed. This study highlights the importance of considering the cooking step in chemical risk assessment procedures and its impact on the level of chemical contaminants in meat and on the formation of potentially toxic breakdown compounds.

Quantification of Serum Sulfamethoxazole and Trimethoprim by Ultra-fast Solid-Phase Extraction-Tandem Mass Spectrometry

BACKGROUND

The combination of trimethoprim (TMP) and sulfamethoxazole (SMX) is used to treat a number of bacterial infections. TMP/SMX concentrations in serum are conventionally monitored using high-performance liquid chromatography (HPLC) or liquid chromatography tandem mass spectrometry. These methods require laborious manual extraction techniques and relatively long sample analysis times, necessitating the development of a simple, high-throughput method. A simple, high-throughput method to measure TMP/SMX using ultra-fast solid-phase extraction (SPE)-tandem mass spectrometry has been developed.

METHODS

Calibration standards, quality control materials, and patient samples were precipitated with acetonitrile containing isotopically labeled internal standards. Samples were vortexed, centrifuged for 5 minutes at 2053g, and the resulting supernatant was diluted in aqueous mobile phase and injected onto the C18 SPE cartridge. MS/MS analysis was performed by electrospray ionization in positive ion mode at a rate of <20 seconds per sample. A 5-point linear 1/x calibration curve was used to calculate sample concentrations.

RESULTS

The intra-assay precision coefficients of variation were <6% and <7% for SMX and TMP, respectively, and <10% for both interassay precision coefficients of variation. Comparison studies using 50 patient and spiked serum samples showed r values of 0.9890 and 0.9853 and y-intercept values of -1.918 and -1.357, respectively compared with the HPLC reference method. All data points were <±15% of the mean. Linearity [r = 0.9952 (SMX) and 0.9954 (TMP)] was established from 12 to 400 mcg/mL with a detection limit of 0.47 mcg/mL, and 1.2-40 mcg/mL with a detection limit of 0.06 mcg/mL, for SMX and TMP, respectively. For either drug, no significant carryover was observed after samples at the upper limit of quantification. No interference was observed from any of the 77 drugs and respective metabolites tested.

CONCLUSIONS

A high-throughput SPE-tandem mass spectrometry method for TMP/SMX quantification was developed. The <20 seconds analysis time is a significant improvement compared with traditional HPLC and liquid chromatography tandem mass spectrometry methods, without sacrificing analytical performance.

Uptake and Disposition of Select Pharmaceuticals by Bluegill Exposed at Constant Concentrations in a Flow-Through Aquatic Exposure System

The increasing use of pharmaceuticals has led to their subsequent input into and release from wastewater treatment plants, with corresponding discharge into surface waters that may subsequently exert adverse effects upon aquatic organisms. Although the distribution of pharmaceuticals in surface water has been extensively studied, the details of uptake, internal distribution, and kinetic processing of pharmaceuticals in exposed fish have received less attention. For this research, we investigated the uptake, disposition, and toxicokinetics of five pharmaceuticals (diclofenac, methocarbamol, rosuvastatin, sulfamethoxazole, and temazepam) in bluegill sunfish (Lepomis macrochirus) exposed to environmentally relevant concentrations (1000-4000 ng L^-1) in a flow-through exposure system. Temazepam and methocarbamol were consistently detected in bluegill biological samples with the highest concentrations in bile of 4, 940, and 180 ng g^-1, respectively, while sulfamethoxazole, diclofenac, and rosuvastatin were only infrequently detected. Over 30-day exposures, the relative magnitude of mean concentrations of temazepam and methocarbamol in biological samples generally followed the order: bile ≫ gut > liver and brain > muscle, plasma, and gill. Ranges of bioconcentration factors (BCFs) in different biological samples were 0.71-3960 and 0.13-48.6 for temazepam and methocarbamol, respectively. Log BCFs were statistically positively correlated to pH adjusted log K_ow (that is, log D_ow), with the strongest relations for liver and brain (r² = 0.92 and 0.99, respectively), implying that bioconcentration patterns of ionizable pharmaceuticals depend on molecular status, that is, whether a pharmaceutical is un-ionized or ionized at ambient tissue pH. Methocarbamol and temazepam underwent rapid uptake and elimination in bluegill biological compartments with uptake rate constants (K_u) and elimination rate constants (K_e) at 0.0066-0.0330 h^-1 and 0.0075-0.0384 h^-1, respectively, and half-lives at 18.1-92.4 h. Exposure to mixtures of diclofenac, methocarbamol, sulfamethoxazole, and temazepam had little or no influence on the uptake and elimination rates, suggesting independent multiple uptake and disposition behaviors of pharmaceuticals by fish would occur when exposed to effluent-influenced surface waters.

Antibiotic pollution in the Katari subcatchment of the Titicaca Lake: Major transformation products and occurrence of resistance genes

An increasing number of studies pointed out the ubiquitous presence of medical residues in surface and ground water as well as in soil compartments. Not only antibiotics can be found in the environment but also their transformation products about which little information is generally available. The development of bacterial resistance to antibiotics is particularly worrying as it can lead to sanitary and health problems. Studies about the dissemination of antibiotics and associated resistances in the Bolivian Altiplano are scarce. We provide baseline information on the occurrence of Sulfamethoxazole (SMX) and Trimethoprim (TMP) antibiotics as well as on the most common human SMX transformation products (TP) and on the occurrence of sulfonamide resistance genes. The studied water and soil compartments presented high levels of antibiotic pollution. This situation was shown to be mainly linked with uncontrolled discharges of treated and untreated wastewaters, resulting on the presence of antibiotics in the Titicaca Lake. SMX TPs were detected in surface waters and on soil sampled next to the wastewater treatment plant (WWTP). SMX resistance genes sulI and sulII were widely detected in the basin hydrological network, even in areas unpolluted with antibiotics. Mechanisms of co-selection of antibiotic- and metal- resistance may be involved in the prevalence of ARG's in pristine areas with no anthropogenic activity and free of antibiotic pollution.

Structural considerations on the selectivity of an immunoassay for sulfamethoxazole

Sulfamethoxazole (SMX), a sulfonamide, is a widely used bacteriostatic antibiotic and therefore a promising marker for the entry of anthropogenic pollution in the environment. SMX is frequently found in wastewater and surface water. This study presents the production of high affinity and selective polyclonal antibodies for SMX and the development and evaluation of a direct competitive enzyme-linked immunosorbent assay (ELISA) for the quantification of SMX in environmental water samples. The crystal structures of the cross-reacting compounds sulfamethizole, N(4)-acetyl-SMX and succinimidyl-SMX were determined by x-ray diffraction aiming to explain their high cross-reactivity. These crystal structures are described for the first time. The quantification range of the ELISA is 0.82-63µg/L. To verify our results, the SMX concentration in 20 environmental samples, including wastewater and surface water, was determined by ELISA and tandem mass spectrometry (MS/MS). A good agreement of the measured SMX concentrations was found with average recoveries of 97-113% for the results of ELISA compared to LC-MS/MS.

Candidate HLA genes for prediction of co-trimoxazole-induced severe cutaneous reactions

BACKGROUND

Co-trimoxazole is a sulfonamide-containing antibiotic that is effective in the treatment of several infections and for prophylaxis of Pneumocystis jiroveci pneumonia. This drug has been reported as a common culprit drug for the Stevens-Johnson syndrome (SJS) and for toxic epidermal necrolysis (TEN). Human leukocyte antigens (HLAs) play a key role in the immunopathogenesis of severe cutaneous reactions induced by several drugs. This study investigated the association between the HLA class I and HLA-DRB1 polymorphisms and co-trimoxazole-induced SJS/TEN in a Thai population.

METHODS

Forty-three patients with co-trimoxazole-induced SJS/TEN and 91 co-trimoxazole-tolerant patients were enrolled in the study. HLA class I and HLA-DRB1 were genotyped using the reverse sequence-specific oligonucleotide probe method.

RESULTS

The frequencies of three alleles of HLA, namely HLA-B*15:02, HLA-C*06:02, and HLA-C*08:01, were significantly higher in the co-trimoxazole-induced SJS/TEN group compared with controls. The risks for co-trimoxazole-induced SJS/TEN in patients with the HLA-B*15:02, HLA-C*06:02, or HLA-C*08:01 allele were about 3-11-fold higher when compared with those who did not carry one of these alleles. Individuals who carried the HLA-B*15:02-C*08:01 haplotype had a 14-fold higher risk for co-trimoxazole-induced SJS/TEN.

CONCLUSION

Evidence of associations between co-trimoxazole-induced SJS/TEN and HLA alleles including HLA-B*15:02, HLA-C*06:02, and HLA-C*08:01 were found in the study population. These findings may suggest that apart from the HLA molecules, other molecules involved in the molecular pathogenesis of these severe cutaneous adverse drug reactions may play an important role in the susceptibility of individuals to SJS/TEN caused by co-trimoxazole.

Tissue-specific bioaccumulation of human and veterinary antibiotics in bile, plasma, liver and muscle tissues of wild fish from a highly urbanized region

We investigated the bioaccumulation of antibiotics in bile, plasma, liver and muscle tissues of wild fish from four rivers in the Pearl River Delta region. In total, 12 antibiotics were present in at least one type of fish tissues from nine wild fish species in the four rivers. The mean values of log bioaccumulation factors (log BAFs) for the detected antibiotics in fish bile, plasma, liver, and muscle tissues were at the range of 2.06-4.08, 1.85-3.47, 1.41-3.51, and 0.48-2.70, respectively. As the digestion tissues, fish bile, plasma, and liver showed strong bioaccumulation ability for some antibiotics, indicating a different bioaccumulation pattern from hydrophobic organic contaminants. Human health risk assessment based on potential fish consumption indicates that these antibiotics do not appear to pose an appreciable risk to human health. To the best of our knowledge, this is first report of bioaccumulation patterns of antibiotics in wild fish bile and plasma.

Structural elucidation of sulfaquinoxaline metabolism products and their occurrence in biological samples using high-resolution Orbitrap mass spectrometry

Four previously unreported metabolism products of sulfaquinoxaline (SQX), a widely used veterinary medicine, were isolated and analyzed using liquid chromatography coupled to high-resolution Orbitrap mass spectrometry. Metabolites were structurally elucidated, and a fragmentation pathway was proposed. The combination of high-resolution MS(2) spectra, linear ion trap MS(2), in-source collision-induced dissociation (CID) fragmentation, and photolysis were used to analyze SQX and its metabolites. All metabolism products identified showed a similar fragmentation pattern to that of the original drug. Differential product ions were produced at m/z 162 and 253 which contain the radical moiety with more 16 Da units than sulfaquinoxaline. This occurs by a hydroxyl attachment to the quinoxaline moiety. With the exception of two low-intensity compounds, all the mass errors were below 5.0 ppm. The distribution of these metabolites in some animal species are also presented and discussed.

Landfill disposal of unused medicines reduces surface water releases

The pharmaceutical industry is conducting research to evaluate the pathways and fate of active pharmaceutical ingredients from the consumer to surface waters. One potential pathway identified by the researchers is the disposal of unused pharmaceutical products that are discarded by consumers in household trash and disposed of in municipal solid waste landfills. This study was designed to evaluate relative amounts of surface water exposures through the landfill disposal pathway compared to patient use and flushing of unused medicine pathways. The estimated releases to surface water of 24 example active pharmaceutical ingredients (APIs) in landfill leachate were calculated for 3 assumed disposal scenarios: 5%, 10%, and 15% of the total annual quantity of API sold is discarded and unused. The estimated releases from landfills to surface waters, after treatment of the leachate, were compared to the total amount of each example API that would be released to surface waters from publicly owned treatment works, generated by patient use and excretion. This study indicates that the disposal of unused medications in municipal solid waste landfills effectively eliminates the unused medicine contribution of APIs to surface waters; greater than 99.9% of APIs disposed of in a landfill are permanently retained.

Nonenzymatic formation of a novel hydroxylated sulfamethoxazole derivative in human liver microsomes: implications for bioanalysis of sulfamethoxazole metabolites

Sulfamethoxazole is metabolized by microsomal CYP2C9 to a hydroxylamine that is thought to be responsible for the relatively high incidence of hypersensitivity reactions associated with the drug. Accurate quantification of the hydroxylamine requires the loss of metabolite through autoxidation to be blocked with ascorbate. In this study, a partly nonenzymatically generated arylhydroxylated derivative of sulfamethoxazole was identified by liquid chromatography/mass spectrometry in incubations of human liver microsomes, and it was found to coelute with the isomeric hydroxylamine under the conditions of three published high-performance liquid chromatography (HPLC) assays. Partial inhibition of the aryl hydroxylation by 1-aminobenzotriazole suggested some involvement of cytochrome P450. However, the formation of this compound was ascorbate-dependent, and it was enhanced by the addition of Fe2+/EDTA and inhibited by desferrioxamine but not by mannitol. These findings are consistent with the phenol being generated via an Fe2+/ascorbate/O2-oxygenating system that does not involve hydroxyl radicals. It was also produced by H2O2/ascorbate. Because the compound shares close chromatographic similarities with the hydroxylamine metabolite, it is possible that previous studies may have inaccurately characterized or quantified sulfamethoxazole metabolism.

Zidovudine plus sulfamethoxazole–trimethoprim adversely affects B lymphocyte maturation in bone marrow of normal mice

Sulfamethoxazole-trimethoprim and zidovudine (AZT), drugs used often in combination in patients infected with HIV, were investigated for their effects on B cell development in a mouse model. BALB/c mice were randomized to receive oral doses of AZT, sulfamethoxazole-trimethoprim, or the combination via oral gavage for up to 28 days. Immune cell populations in the spleen, lung, and peripheral blood were examined, and toxicity to B lineage subtypes in the bone marrow was investigated by phenotypic analysis via flow cytometry. Pre-pro-B, pro-B, early pre-B, and late pre-B cells were assayed for apoptosis and analyzed for cell cycle profile. Total as well as B cell splenic and bone marrow cellularities were significantly decreased by using the drugs concomitantly, while B cell populations in the lungs and percentage in the peripheral blood were not affected. Combination therapy caused significant increases in apoptosis in B cells and granulocytes in the bone marrow, with the late pre-B cell population being the most depleted. The proliferative expansion and differentiation of early pre-B cells (B220+/CD43+/BP-1+/HSA+) to the late pre-B cell (B220+/CD43-/IgM-) stage was blocked, with early pre-B cells accumulating in the proliferative phases of the cell cycle. This apoptosis increase is likely due to elevated blood sulfamethoxazole concentrations that were observed in mice also receiving AZT. Concurrent sub-chronic administration of AZT and sulfamethoxazole-trimethoprim adversely affected B lymphocyte development in mouse bone marrow.

A flow injection sensor for simultaneous determination of sulfamethoxazole and trimethoprim by using Sephadex SP C-25 for continuous on-line separation and solid phase UV transduction

A flow-through sensor based on integration of spectrophotometric detection and the different kinetics of retention/elution of analytes on a solid support is proposed for the simultaneous determination of sulfamethoxazole (SMZ) and trimethoprim (TMP). The solid support (Sephadex SP C-25) fills both, a microcolumn placed on-line and the sensing microzone. The intrinsic absorbance of both compounds is monitored directly on the solid phase at 269 nm and so, no derivatization step is required. Using two alternate solutions, 10(-4) M hydrochloric acid and 0.20 M NaAc/HAc (pH 5.0) buffer, the sensor responds linearly in the measuring range of 50-250 and 10-70 microg ml(-1) with detection limits of 9.5 and 0.6 microg ml(-1) (500 microl of sample volume) for SMZ and TMP, respectively. The main advantages of the sensor are simplicity, rapidity and low reagents consumption. Its application to SMZ and TMP determination in synthetic samples and pharmaceutical preparations is demonstrated. The results obtained by the proposed method were compared with those obtained by a standard HPLC method.

Circadian changes in pharmacokinetics of sulfamethoxazole administered orally to rabbits

Circadian variations of sulfamethoxazole pharmacokinetics were studied after a single oral administration of sulfamethoxazole, 50 mg/kg, to rabbits at 09:00 (a.m.) and 22:00 (p.m.). The profiles of plasma sulfamethoxazole concentration showed from 6 h to 24 h significant statistical difference (p<0.05) between 09:00 and 22:00. The half-life (t(1/2)) was significantly shorter in the morning (11.2 +/- 3.2 h) when compared to the nighttime (15.4 +/- 3.5 h) (p< 0.05). The AUC was significantly decreased in the morning (1325 +/- 264 microg/ml x h) than that in the nighttime (2059 +/- 379 microg/ml x h) (p<0.05). Total body clearance (CLt) was significantly higher when sulfamethoxazole was given in the morning (6.65 +/- 0.23 ml/min) versus in the nighttime (4.28 +/- 0.20 ml/min) (p<0.05).

Association analysis of drug metabolizing enzyme gene polymorphisms in HIV-positive patients with co-trimoxazole hypersensitivity

The use of co-trimoxazole in HIV-positive patients has been associated with a high frequency (40-80%) of hypersensitivity reactions. This has been attributed to the bioactivation of the sulphonamide component, sulphamethoxazole (SMX), to its toxic hydroxylamine and nitroso metabolites. The aim of this study was to determine whether functionally significant polymorphisms in the genes coding for enzymes involved in SMX metabolism influence susceptibility to SMX hypersensitivity. HIV-positive patients with (n = 56) and without (n = 89) SMX hypersensitivity were genotyped for allelic variants in CYP2C9, GSTM1, GSTT1, GSTP1 and NAT2 using polymerase chain reaction (PCR) and/or PCR-restriction fragment length polymorphism analysis. The CYP2C9*2/*3 genotype and CYP2C9*3 allele frequencies were nine- and 2.5-fold higher in the hypersensitive group compared to non-sensitive patients, respectively, although they were not statistically significant when corrected for multiple testing. There were no differences in the frequencies of the GSTM1 and GSTT1 null genotypes, and the slow acetylator genotype, between hypersensitive and non-sensitive patients, while GSTP1 frequency was lower (although non-significant) in the hypersensitive group [21% versus 32%, odds ratio (OR) = 0.5, Pc = 0.24]. Comparison of the genotype frequencies in HIV-positive and -negative patients showed that the NAT2 slow acetylator genotype frequency in the HIV-positive patients (74%) was significantly (Pc = 0.0003, OR = 2.3) higher than in control subjects (56%). Our results show that genetic polymorphisms in drug metabolizing enzymes are unlikely to be major predisposing factors in determining individual susceptibility to co-trimoxazole hypersensitivity in HIV-positive patients.

Achiral and chiral determination of ciprofibrate and its glucuronide in human urine by capillary electrophoresis

A method for achiral separation of the racemic hypolipidaemic agent ciprofibrate and its main metabolite ciprofibrate glucuronide by capillary electrophoresis (CE) was developed. The glucuronide was isolated from urine by chromatographic procedures and characterized by alkaline as well as enzymatic hydrolysis and mass spectrometric and nuclear magnetic resonance experiments. Chiral discrimination of the ciprofibrate enantiomers and their diastereomeric glucuronides by CE was achieved by the use of gamma-cyclodextrin as buffer additive. The fractionated crystallization of ciprofibrate yielded the R-(+)-enantiomer as less soluble diastereomeric salt with (+)-1-phenylethylamine. This allowed the identification of the enantiomers of ciprofibrate as well as the diastereomeric glucuronides of ciprofibrate by CE. In a study with three volunteers inter- and intra-individual differences of ratios of both ciprofibrate glucuronides in urine were observed. After oral administration of a single dose of the racemate the S-ciprofibrate glucuronide was mainly excreted in the first time intervals, in the last time intervals the R-glucuronide dominated.

Determination of antibiotics in different water compartments via liquid chromatography-electrospray tandem mass spectrometry

For the determination of 18 antibiotics in water samples down to the lower ng/l range, an analytical multi method is presented. The analytes belong to different groups of antibiotics such as penicillins, tetracyclines, sulfonamides and macrolid antibiotics. Samples were enriched using a universal freeze-drying procedure or a solid-phase extraction facultatively. Analysis was performed by liquid chromatography with electrospray-tandem MS detection. Chromatography required different columns and eluents. Mean recovery rates were in excess of 70%, however, with one exception and a quantitation limit of 50 ng/l for the tetracyclines and 20 ng/l for all other antibiotics were set.

Isolation, identification and determination of sulfadiazine and its hydroxy metabolites and conjugates from man and rhesus monkey by high-performance liquid chromatography

The following metabolites of sulfadiazine (S) were isolated from monkey urine by preparative HPLC: 5-hydroxysulfadiazine (5OH), 4-hydroxysulfadiazine (4OH) and the glucuronide (5OHgluc) and sulfate conjugate of 5OH (5OHsulf). The compounds were identified by NMR, mass and infrared spectrometry and hydrolysis by beta-glucuronidase. The analysis of S, the hydroxymetabolites (4OH, 5OH) and conjugates N4-acetylsulfadiazine (N4), 5OHgluc and 5OHsulf in human and monkey plasma and urine samples was performed using reversed-phase gradient HPLC with UV detection. In plasma, S and N4 could be detected in high concentrations, whereas the other metabolites were present in only minute concentrations. In urine, S, the metabolites and conjugates were present. The limit of quantification of the compounds in plasma varies between 0.2 and 0.6 microgram/ml (S 0.31, N4 0.40, 4OH 0.20, 5OH 0.37, 5OHgluc 0.33 and 5OHsulf 0.57 microgram/ml). In urine it varies between 0.6 and 1.1 micrograms/ml (S 0.75, N4 0.80, 4OH 0.60, 5OH 0.80, 5OHgluc 0.80 and 5OHsulf 1.1 micrograms/ml). The method was applied to studies with healthy human subjects and Rhesus monkeys. The metabolites 5OH, 5OHgluc and 5OHsulf were present in Rhesus monkey and not in man. Preliminary results of studies of metabolism and pharmacokinetics in Rhesus monkey and man are presented.

Urinary recovery and kinetics of sulphamethoxazole and its metabolites in HIV-seropositive patients and healthy volunteers after a single oral dose of sulphamethoxazole

1. The urinary excretion of sulphamethoxazole and its metabolites was compared between healthy volunteers and HIV-seropositive patients in order to get a better understanding of why HIV seropositives are more predisposed to idiosyncratic toxicity of sulphonamides. 2. A single 800 mg oral dose of sulphamethoxazole was administered to seven healthy volunteers and seven asymptomatic HIV seropositives without previous use of sulphonamides. 3. Urine was collected for 4 days and drug analysis was by h.p.l.c. 4. No difference was observed between seropositive and seronegative individuals in the urinary recovery of sulphamethoxazole, N4-acetyl-, 5-hydroxy-, N4-acetyl-5-hydroxy-sulphamethoxazole and the N1-glucuronide conjugate. However the recovery of the hydroxylamine metabolite of sulphamethoxazole was significantly lower in the HIV seropositives (0.50 +/- 0.51 vs 2.23 +/- 0.85%; 95% CI on the difference, -0.90 to -2.55; P = 0.0006). 5. Sulphamethoxazole hydroxylamine may be a factor in the susceptibility of HIV infected individuals to sulphonamides.