CuCo2O4/N-Doped CNTs loaded with molecularly imprinted polymer for electrochemical sensor: Preparation, characterization and detection of metronidazole.

CuCo2O4 nanoparticles modified with nitrogen doped carbon nanotubes (CuCo2O4/N-CNTs) have high specific surface area and good electrical conductivity. Herein, a novel electrochemical sensor based on CuCo2O4/N-CNTs loaded molecularly imprinted polymer (MIP) modified glassy carbon electrode (GCE) is proposed for rapid and ultrasensitive detection of metronidazole (MNZ). The composite of CuCo2O4/N-CNTs with MIP significantly enhances the electrical signal. The electrochemical polymerization was performed with MNZ as template and aniline as functional monomer by cyclic voltammetry (CV), and differential pulse voltammetry (DPV) was used to detect MNZ. Factors that affect sensor response were optimized. Under the optimal experimental conditions, the DPV current response shows two linearity ranges for MNZ in the range of 0.005-0.1 µM and 0.1-100 µM with very low limit of detection (LOD) of 0.48 nM (S/N = 3). This electrochemical sensing system has high sensitivity, selectivity, excellent reproducibility, repeatability and stability. The recovery (95.9%-100.9%) and reasonable relative standard deviation (RSD) (3.2%-4.8%) for determination of real samples indicate the practicality of the sensing system. This sensing system has high potential for rapid determination of MNZ in samples such as metronidazole tablets, human serum and urine.

The sex-specific association between maternal paraben exposure and size at birth.

Parabens are a group of esters of parahydroxybenzoic acid and are utilized as antimicrobial preservatives in the majority of personal care products (PCPs). Epidemiological studies regarding the adverse effects of parabens on fetuses are still limited. The aim of this study was to determine the association between maternal paraben exposure and birth outcomes. One hundred and ninety-nine pregnant women were enrolled, and maternal urine was collected in the third trimester. The urine concentrations of four parabens (methyl (MP), ethyl (EP), propyl (PP), and butyl (BP)) were determined by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Generalized additive model-penalized regression splines and a multivariable regression model were employed to determine the association between paraben exposure levels and birth outcomes. A causal mediation analysis was conducted to determine the mediation effect of oxidative stress on birth outcomes. The geometric means of urinary MP, EP, PP, and BP were 51.79, 1.26, 4.21, and 1.25 µg/g cre., respectively. In the penalized regression splines, sex-specific associations between maternal MP levels and birth outcomes were observed; a downward curvature was observed between the MP level and birth weight, length, head circumference, and thoracic circumference among female newborns. Pregnant women in the group with MP levels above the third quartile had neonates with significantly lower body weight (ß = -215.98 g, p value = 0.02) compared to those in the group with MP levels lower than the third quartile. No significant mediation of oxidative stress was observed between maternal MP exposure and female birth weight. The estimated proportion mediated ranged from -6% to 15%. The negative association between maternal paraben exposure and female birth outcomes in relation to child development should be carefully considered.

Paraben exposures and asthma-related outcomes among children from the US general population.

BACKGROUND: Parabens are synthetic preservatives present in many consumer products. Their antimicrobial and endocrine-disrupting properties have raised concerns that they might play a role in respiratory and allergic diseases; however, studies exploring these associations are scarce. OBJECTIVE: We examined the cross-sectional association between parabens and asthma morbidity among 450 children with asthma and with asthma prevalence among 4023 children in the US general population participating in the National Health and Nutrition Examination Survey (2005-2014). METHODS: We conducted multivariable logistic regression to examine associations between urinary paraben biomarker concentrations (butyl paraben, ethyl paraben, methyl paraben [MP], and propyl paraben [PP]) and asthma attacks and emergency department visits among children with asthma and with a current asthma diagnosis among all children. We also examined heterogeneity of associations by sex. RESULTS: We observed an increased prevalence odds of reporting emergency department visits for every 10-fold increase in MP and PP concentrations among boys with asthma (adjusted prevalence odds ratio, 2.61 [95% CI, 1.40-4.85] and 2.18 [95% CI, 1.22-3.89, respectively; Pinteraction-MP = .002 and Pinteraction-PP = .003); associations remained after adjusting for other phenolic compounds previously linked to respiratory outcomes. No other dimorphic effects of exposure by sex were observed. Among children in the general population, no overall associations with current asthma were observed, although there was a positive trend with PP and a current asthma diagnosis. CONCLUSION: We identified differential effects of exposure to select parabens by sex on asthma morbidity. Further studies are needed to replicate these findings and elucidate mechanisms by which parabens could affect respiratory health and elicit dimorphic effects by sex.

Triclosan in over the counter medicines of South China.

Triclosan (TCS) is an endocrine disruptor which may affect endocrine function, antibiotic resistance, and thyroid hormone homeostasis. As a broad-spectrum antimicrobial agent used in medical and personal care products, TCS was frequently detected in human urine, indicating widespread human exposure to this chemical. Over-the-counter medicines (OTCs) may be a potential source of human exposure to TCS. In this study, 84 OTCs were collected from Guangzhou, South China, including medicines intended for both children and adults. We determined the concentration of TCS in OTCs and the estimated daily intakes (EDIs) of TCS by evaluating OTCs for different age groups of the Chinese population. Our results indicated over half of the evaluated medicines contained TCS and the highest concentration reached 7.825 ng/g, with a median value of 0.017 ng/g. TCS was frequently found in adult medicines (detected in 85% of samples), and the concentrations were significantly higher than those in children's medicines. TCS in OTCs may come from packaging materials, cultivated soils, or production process (Chinese patent medicines). The EDIs of TCS (estimated with 95th concentration in OTC medicines) were 0.305, 0.191, 0.287, 0.331, and 0.135 and 0.110 ng/kg-bw/day for infants, toddlers, children, teenagers, and adult females and males, respectively. Compared to other potential sources, human exposure to TCS from OTCs was limited in China-much less than TCS exposure through personal care products or indoor dust.

Male urinary biomarkers of antimicrobial exposure and bi-directional associations with semen quality parameters.

Antimicrobials including parabens, triclosan, and triclocarban have endocrine disrupting properties. Among 501 male partners of couples planning to become pregnant, preconception urinary biomarkers of parabens, triclosan and triclocarban exposure were quantified in spot urine samples. Men also provided two fresh semen samples collected approximately one month to undergo 24-h semen quality analysis. Linear mixed-effects models, adjusted for creatinine, race, age and body mass index, were utilized to assess the relationship between log transformed chemical concentrations rescaled by their standard deviations and semen parameters. Methyl, ethyl and butyl parabens, were associated with diminished sperm count and several sperm motility parameters. Hydroxylated paraben metabolites and triclosan were significantly positively associated with select semen quality parameters. Overall, our findings suggest that specific urinary parabens found in consumer goods (methyl, ethyl and butyl parabens) may adversely impact sperm quality parameters among reproductive-age male partners of couples trying for pregnancy.

Green synthesis of graphitic carbon nitride nanosheet (g-C3N4) and using it as a label-free fluorosensor for detection of metronidazole via quenching of the fluorescence.

In this research, g-C3N4nanosheets were facilely fabricated by thermal polymerization and then exfoliated into ultrathin nanosheets through ultrasonication in water media. Low-cost C-N nanosheets prepared by melamine possessed a highly π-conjugated structure and fluorescence property. In the present study, the g-C3N4nanosheet was used as a switch-off fluorescence sensor for rapid and sensitive sensing of metronidazole in biological fluids. These nanosheets were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The fluorescence of the solution of the g-C3N4nanosheets was quenched effectively by metronidazole through two mechanisms: fluorescence resonance energy transfer and the formation of a donor-acceptor charge-transfer complex between π-electron rich donors. Under optimal conditions, the detection linear range for metronidazole was found to be from 0.01 to 0.10µgml-1, with a limit of detection (LOD) of 0.008µgml-1 which can cover standard range of metronidazole in real samples. Moreover, the proposed method has offered a green, rapid, and sensitive probe for quantitative determination of metronidazole in drug and biological fluids.

Clinical Pharmacokinetics of Levornidazole in Elderly Subjects and Dosing Regimen Evaluation Using Pharmacokinetic/Pharmacodynamic Analysis.

PURPOSE: Levornidazole, the levo-isomer of ornidazole, is a third-generation nitroimidazole derivative newly developed after metronidazole, tinidazole, and ornidazole. An open-label, parallel-controlled, single-dose study was conducted for the investigation of the pharmacokinetic (PK) profile of levornidazole and its metabolites in healthy elderly Chinese subjects, and for the evaluation of 2 dosing regimens in the elderly. METHODS: Levornidazole was intravenously administered at 500 mg to healthy elderly (aged 60-80 years) or young subjects (aged 19-45 years). The PK profiles of levornidazole and its metabolites in elderly subjects were evaluated and compared with those in the young group. WinNonlin software was used for simulating the PK profile of levornidazole in the elderly population following the dosing regimens of 500 mg BID and 750 mg once daily for 7 days. Monte Carlo simulation was used for estimating the cumulative fraction of response and probability of target attainment of both dosing regimens against Bacteroides spp. RESULTS: The Cmax, AUC0-24, and AUC0-∞ values of levornidazole in the elderly group were 11.98 µg/mL, 131.36 µg·h/mL, and 173.61 µg·h/mL, respectively. The t1/2, CLt, and mean residence time from time 0 to infinity were 12.21 hours, 2.91 L/h, and 16.46 hours. The metabolic ratios of metabolites (M) 1, 2, 4, and 6 were <3.0%, and that of M16 was 17.70%. The urinary excretion values of levornidazole, M1, M2, M4, M6, and M16 over 96 hours were 10.21%, 0.92%, ~0%, 2.69%, 0.54%, and 41.98%. The PK properties of levornidazole and the urinary excretion of all metabolites were not statistically different between the 2 groups. The cumulative fraction of response was >90% against B fragilis and other Bacteroides spp, and the probability of target attainment was >90% when the minimum inhibitory concentration was ≤1 µg/mL, in both groups. IMPLICATIONS: No dosing regimen adjustment is suggested when levornidazole is used in elderly patients with normal hepatic functioning and mild renal dysfunction. The findings from the PK/PD analysis imply that both regimens may achieve satisfactory clinical and microbiological efficacy against anaerobic infections in elderly patients. Chinese Clinical Trial Registry (http://www.chictr.org.cn) identifier: ChiCTR-OPC-16007938.

Dual-cloud point extraction coupled to high performance liquid chromatography for simultaneous determination of trace sulfonamide antimicrobials in urine and water samples.

Dual-cloud point extraction (dCPE) was successfully developed for simultaneous extraction of trace sulfonamides (SAs) including sulfamerazine (SMZ), sulfadoxin (SDX), sulfathiazole (STZ) in urine and water samples. Several parameters affecting the extraction were optimized, such as sample pH, concentration of Triton X-114, extraction temperature and time, centrifugation rate and time, back-extraction solution pH, back-extraction temperature and time, back-extraction centrifugation rate and time. High performance liquid chromatography (HPLC) was applied for the SAs analysis. Under the optimum extraction and detection conditions, successful separation of the SAs was achieved within 9min, and excellent analytical performances were attained. Good linear relationships (R2≥0.9990) between peak area and concentration for SMZ and STZ were optimized from 0.02 to 10µg/mL, for SDX from 0.01 to 10µg/mL. Detection limits of 3.0-6.2ng/mL were achieved. Satisfactory recoveries ranging from 85 to 108% were determined with urine, lake and tap water spiked at 0.2, 0.5 and 1µg/mL, respectively, with relative standard deviations (RSDs, n=6) of 1.5-7.7%. This method was demonstrated to be convenient, rapid, cost-effective and environmentally benign, and could be used as an alternative tool to existing methods for analysing trace residues of SAs in urine and water samples.

Urinary Concentrations of Parabens and Other Antimicrobial Chemicals and Their Association with Couples' Fecundity.

BACKGROUND: Human exposure to parabens and other antimicrobial chemicals is continual and pervasive. The hormone-disrupting properties of these environmental chemicals may adversely affect human reproduction. OBJECTIVE: We aimed to prospectively assess couples' urinary concentrations of antimicrobial chemicals in the context of fecundity, measured as time to pregnancy (TTP). METHODS: In a prospective cohort of 501 couples, we examined preconception urinary chemical concentrations of parabens, triclosan and triclorcarban in relation to TTP; chemical concentrations were modeled both continuously and in quartiles. Cox's proportional odds models for discrete survival time were used to estimate fecundability odds ratios (FORs) and 95% confidence intervals (CIs) adjusting for a priori-defined confounders. In light of TTP being a couple-dependent outcome, both partner and couple-based exposure models were analyzed. In all models, FOR estimates < 1.0 denote diminished fecundity (longer TTP). RESULTS: Overall, 347 (69%) couples became pregnant. The highest quartile of female urinary methyl paraben (MP) concentrations relative to the lowest reflected a 34% reduction in fecundity (aFOR = 0.66; 95% CI: 0.45, 0.97) and remained so when accounting for couples' concentrations (aFOR = 0.63; 95% CI: 0.41, 0.96). Similar associations were observed between ethyl paraben (EP) and couple fecundity for both partner and couple-based models (p-trend = 0.02 and p-trend = 0.05, respectively). No associations were observed with couple fecundity when chemicals were modeled continuously. CONCLUSIONS: Higher quartiles of preconception urinary concentrations of MP and EP among female partners were associated with reduced couple fecundity in partner-specific and couple-based exposure models.

A fabric phase sorptive extraction-High performance liquid chromatography-Photo diode array detection method for the determination of twelve azole antimicrobial drug residues in human plasma and urine.

This paper reports a novel fabric phase sorptive extraction-high performance liquid chromatography-photodiode array detection (FPSE-HPLC-PDA) method for the simultaneous extraction and analysis of twelve azole antimicrobial drug residues that include ketoconazole, terconazole, voriconazole, bifonazole, clotrimazole, tioconazole, econazole, butoconazole, miconazole, posaconazole, ravuconazole, and itraconazole in human plasma and urine samples. The selected azole antimicrobial drugs were well resolved by using a Luna C18 column (250mm×4.6mm; 5µm particle size) in gradient elution mode within 36min. The analytical method was calibrated and validated in the range from 0.1 to 8µg/mL for all the drug compounds. Blank human plasma and urine were used as the sample matrix for the analysis; while benzyl-4-hydroxybenzoate was used as the internal standard (IS). The limit of quantification of the FPSE-HPLC-PDA method was found as 0.1µg/mL and the weighted-matrix matched standard calibration curves of the drugs showed a good linearity upto a concentration of 8µg/mL. The parallelism tests were also performed to evaluate whether overrange sample can be analyzed after dilution, without compromising the analytical performances of the validated method. The intra- and inter-day precision (RSD%) values were found ≤13.1% and ≤13.9%, respectively. The intra- and inter-day trueness (bias%) values were found in the range from -12.1% to 10.5%. The performances of the validated FPSE-HPLC-PDA were further tested on real samples collected from healthy volunteers after a single dose administration of itraconazole and miconazole. To the best of our knowledge, this is the first FPSE extraction procedure applied on plasma and urine samples for the simultaneous determination of twelve azole drugs possessing a wide range of logKow values (extending from 0.4 for fluconazole to 6.70 of butoconazole) and could be adopted as a rapid and robust green analytical tool for clinical and pharmaceutical applications.

Salting-out homogenous extraction followed by ionic liquid/ionic liquid liquid-liquid micro-extraction for determination of sulfonamides in blood by high performance liquid chromatography.

Salting-out homogenous extraction followed by ionic liquid/ionic liquid dispersive liquid-liquid micro-extraction system was developed and applied to the extraction of sulfonamides in blood. High-performance liquid chromatography was applied to the determination of the analytes. The blood sample was centrifuged to obtain the serum. After the proteins in the serum were removed in the presence of acetonitrile, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, dipotassium hydrogen phosphate, ionic liquid 1-Hexyl-3-methylimidazolium hexafluorophosphate were added into the resulting solution. After the resulting mixture was ultrasonically shaken and centrifuged, the precipitate was separated. The acetonitrile was added in the precipitate and the analytes were extracted into the acetonitrile phase. The parameters affecting the extraction efficiency, such as volume of ionic liquid, amount of dipotassium hydrogen phosphate, volume of dispersant, extraction time and temperature were investigated. The limits of detection of sulfamethizole (STZ), sulfachlorpyridazine (SCP), sulfamethoxazole (SMX) and Sulfisoxazole (SSZ) were 4.78, 3.99, 5.21 and 3.77µgL-1, respectively. When the present method was applied to the analysis of real blood samples, the recoveries of analytes ranged from 90.0% to 113.0% and relative standard deviations were lower than 7.2%.

Carbon paste electrode modified with duplex molecularly imprinted polymer hybrid film for metronidazole detection.

A novel electrochemical sensor based on duplex molecularly imprinted polymer (DMIP) hybrid film modified carbon paste electrode (CPE) has been developed for highly sensitive and selective determination of metronidazole (MNZ). A conductive poly(anilinomethyltriethoxysilane) film is firstly electrodeposited on the surface of a CPE, and then a molecularly imprinted polysiloxane (MIPS) membrane is covalently covered on the film via sol-gel process. The as-constructed DMIP hybrid film, combining the advantages of MIPS and conducting MIP, can make feasible the direct and efficient signal transformation between the target analyte and the transducer, as well as enhance the imprinting recognition capability, mass transfer efficiency and the detection sensitivity. Under optimized conditions, the reduction peak currents of MNZ are linear to MNZ concentrations in the range from 4.0×10(-7) to 2.0×10(-4) molL(-1) with a detection limit of 9.1×10(-8)molL(-1). The RSD values vary from 2.9% to 4.7% for intra-day and from 3.4% to 4.2% for inter-day precision. The DMIP-based sensor has been successfully applied for the determination of MNZ in biological and pharmaceutical samples. The accuracy and reliability of the method is further confirmed by high performance liquid chromatography.

Multiple response optimization of a liquid chromatographic method for determination of fluoroquinolone and nitroimidazole antimicrobials in serum and urine.

OBJECTIVES: Development and validation of a sensitive, selective and robust SPE assisted HPLC method for the quantification of fluoroquinolones and nitroimidazoles in human serum and urine using design of experiments methodology. DESIGN AND METHODS: Design of experiments was employed for method optimization (Box-Behnken design) and robustness testing (Plackett-Burman design). Sample preparation involved a simple solid phase extraction, which offered a satisfactory recovery (≥94%). Analytes were separated on a phenyl hexyl column with mobile phase comprising water, acetonitrile and triethyl amine in ratio of 74:26:0.15 v/v, with a flow rate of 1.1mL/min. RESULTS: Calibration curves were linear over selected range (≥0.995) for all the analytes. The method was sensitive with detection limits of 0.06-0.16µg/mL in serum and urine samples. Inter and intra-day precision data (in terms of %RSD) was found to be less than 7%. Stability studies were carried out to assess freeze thaw, short term and long term stability and all analytes were found to be stable. The method was successfully applied for determination of antimicrobial drugs in spiked serum and urine. CONCLUSION: The obtained results corroborated the potential of the proposed method for determination of all the four antimicrobial drugs in therapeutic drug monitoring, bioequivalence and drug-drug interaction studies.

Urinary biomarkers of exposure to 57 xenobiotics and its association with oxidative stress in a population in Jeddah, Saudi Arabia.

Oxidative stress arises from excessive free radicals in the body and is a trigger for numerous diseases, such as cancer and atherosclerosis. Elevated exposure to environmental chemicals can contribute to oxidative stress. The association between exposure to xenobiotics and oxidative stress, however, has rarely been studied. In this study, urinary concentrations of 57 xenobiotics (antimicrobials, parabens, bisphenols, benzophenones, and phthalates metabolites) were determined in a population from Jeddah, Saudi Arabia, to delineate association with the oxidative stress biomarker, 8-hydroxy-2'-deoxyguanosine (8OHDG). We collected 130 urine samples and analyzed for 57 xenobiotics using liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods. The association between unadjusted and creatinine- or specific gravity-adjusted concentrations of xenobiotics and 8OHDG was examined by Pearson correlations and multiple regression analysis. High concentrations of mCPP (a metabolite of di-n-octyl phthalate; DnOP) and mCMHP (a metabolite of diethylhexyl phthalate; DEHP) were found in urine. In addition, the concentrations of bisphenol S (BPS) were higher than those of bisphenol A (BPA). The concentrations of metabolites of DEHP, phthalic acid, BPA, BPS, and methyl-protocatechuic acid were significantly associated with 8OHDG. This is the first biomonitoring study to report exposure of the Saudi population to a wide range of environmental chemicals and provides evidence that environmental chemical exposures contribute to oxidative stress.

Role of an electronic antimicrobial alert system in intensive care in dosing errors and pharmacist workload.

BACKGROUND: Critically ill patients are vulnerable to dosing errors. We developed an electronic Antimicrobial Dose alert based upon Creatinine clearance (ADC-alert), which gives daily antimicrobial dosing advice based upon the 24-h creatinine clearance (CLcr). OBJECTIVE: Primary objective: to verify the correctness of the ADC-alert output and its benefit for the workload of the clinical pharmacist (CP). Secondary objective to compare the ADC-alert output between patients with normal and impaired CLcr. SETTING: The 36-bed surgical and medical intensive care unit (ICU) of the Ghent University Hospital, Ghent, Belgium. METHOD: In a single centre prospective observational 44-day study, prescriptions were reviewed by CP and compared with the ADC-alert output advice. CP workload was calculated with and without the use of the ADC-alert. Impaired renal function was defined as a CLcr < 50 mL/min for at least 1 day during antimicrobial treatment in the ICU or the need for renal replacement therapy (RRT). MAIN OUTCOME MEASURES: Correct dosing recommendation by ADC-alert compared to CP review and time spent by CP with and without the ADC-alert. RESULTS: A total of 87 patients (554 daily antimicrobial prescriptions; 435 patient days) were both screened by CP and ADC-alert. Renal function impairment occurred in 39 patients (44.8 %) with 12 patients requiring RRT. The ADC-alert gave a correct dosage advice in 483 prescriptions (87.2 %). The overall sensitivity was 77.3 %; specificity was 89.9 %. Use of the ADC-alert reduces CP workload with 76.5 % (average time spent per patient: 17 vs. 4 min). Patients with a CLcr < 50 mL/min less frequently received a correct recommendation than patients with normal CLcr (P = 0.001). This was due to configuration problems in dialysis patients. CONCLUSION: We developed and evaluated an electronic alert system to generate dynamic antimicrobial dose adaptation based on the daily calculation of the 24-h CLcr of ICU patients. Its use led to substantial time savings for clinical pharmacists. However, the alert advice suffered from some developmental and other flaws. Despite resolving some of these shortcomings, bedside interpretation of the results and clinical judgement remain necessary.

Cystatin C as a potential biomarker for dosing of renally excreted drugs.

The objective of the present study was to review the available pharmacokinetic evidence for the utility of cystatin C (CysC) as a marker of renal function to predict the dose of renally excreted drugs.The bibliographic search used PubMed and EMBASE databases, from its inception through to January 2014, with the following keywords 'pharmacokinetics' and 'cystatin C'.Sixteen pharmacokinetic publications were identified and seven drugs primarily excreted by the kidney were studied. Among them, only one study was performed in children, the others were performed in adults and/or elderly subjects, either healthy volunteers or patients with variable clinical conditions, such as cystic fibrosis and cancer. Most of studies (n = 13/16) demonstrated that CysC was better correlated with clearance/trough concentration of evaluated drugs compared with creatinine.Our review supports that CysC is a good marker of renal function to predict dose of renally excreted drugs. Efforts should be made to evaluate the impact of CysC in special populations in order to define its clinical value in dosing optimization.

Urinary biomarkers of trimethoprim bioactivation in vivo following therapeutic dosing in children.

The antimicrobial trimethoprim-sulfamethoxazole (TMP-SMX) is widely used for the treatment of skin and soft-tissue infections in the outpatient setting. Despite its therapeutic benefits, TMP-SMX has been associated with a number of adverse drug reactions, which have been primarily attributed to the formation of reactive metabolites from SMX. Recently, in vitro experiments have demonstrated that TMP may form reactive intermediates as well. However, evidence of TMP bioactivation in patients has not yet been demonstrated. In this study, we performed in vitro trapping experiments with N-acetyl-l-cysteine (NAC) to determine stable markers of reactive TMP intermediates, focusing on eight potential markers (NAC-TMP adducts), some of which were previously identified in vitro. We developed a specific and sensitive assay involving liquid chromatography followed by tandem mass spectrometry for measurement of these adducts in human liver microsomal samples and expanded the methodology toward the detection of these analytes in human urine. Urine samples from four patients receiving TMP-SMX treatment were analyzed, and all samples demonstrated the presence of six NAC-TMP adducts, which were also detected in vitro. These adducts are consistent with the formation of imino-quinone-methide and para-quinone-methide reactive intermediates in vivo. As a result, the TMP component of TMP-SMX should be considered as well when evaluating adverse drug reactions to TMP-SMX.

Kinetic spectrophotometric H-point standard addition method for the simultaneous determination of diloxanide furoate and metronidazole in binary mixtures and biological fluids.

Simple, reliable, and sensitive kinetic spectrophotometric method has been developed for the simultaneous determination of diloxanide furoate and metronidazole using H-point standard addition method (HPSAM). The method is based on the oxidation rate difference of diloxanide and metronidazole by potassium permanganate in basic medium. A green color has been developed and measured at 610 nm. Different experimental parameters were carefully optimized. The limiting logarithmic and the initial-rate methods were adopted for the construction of the calibration curve of each individual reaction with potassium permanganate. Under the optimum conditions, Beer's law was obeyed in the range of 1.0-20.0 and 5.0-25.0 µg ml(-1) for diloxanide furoate and metronidazole, respectively. The detection limits were 0.22 µg ml(-1) for diloxanide furoate and 0.83 µg ml(-1) for metronidazole. Correlation coefficients of the regression equations were greater than 0.9970 in all cases. The precision of the method was satisfactory; the maximum value of relative standard deviation did not exceed 1.06% (n=5). The accuracy, expressed as recovery was between 99.4% and 101.4% with relative error of 0.12 and 0.14 for diloxanide furoate and metronidazole, respectively. The proposed method was successfully applied for the simultaneous determination of both drugs in pharmaceutical dosage forms and human urine samples and compared with alternative HPLC method.