[Determination of 1-methoxy-2-propanol in urine by headspace solid-phase microextraction coupled with gas chromatography].

Objective: To establish a method for the determination of 1-methoxy-2-propanol in urine using headspace solid phase micro-extraction coupled with gas chromatography. Methods: The 1-methoxy-2-propanol was enriched by headspace solid phase micro-extraction fiber coated with carbene/polydimethylsiloxane (CAR/PDMS) . Single factor rotation method was used to optimize the conditions of extraction temperature, salt amount, and extraction time. The separation was performed on DB-5 (30 m×0.32 mm×0.25 µm) capillary column and detected with flame ionization detector. The quantification was based on the standard curve. Results: The concentration of 1-methoxy-2-propanol in urine was linear in the range of 0.50-10.0 mg/L, and the linear correlation coefficient was 0.9993. The detection limit of the method was 0.14 mg/L, and the limit of quantification was 0.45 mg/L. The recovery was 85.8% to 104.7%, and the RSD of intra- and inter-batch precision were 3.25%-6.65% and 0.81%-3.96%, respectively. Conclusion: The method is high sensitivity and simple operation, and is suitable for the determination of 1-methoxy-2-propanol in urine of occupational exposure population.

Sex differences in urinary levels of several biological indicators of exposure: a simulation study using a compartmental-based toxicokinetic model.

Toxicokinetic modeling is a useful tool to describe or predict the behavior of a chemical agent in the human or animal organism. A general model based on four compartments was developed in a previous study to quantify the effect of human variability on a wide range of biological exposure indicators. The aim of this study was to adapt this existing general toxicokinetic model to three organic solvents--methyl ethyl ketone, 1-methoxy-2-propanol, and 1,1,1,-trichloroethane--and to take into account sex differences. In a previous human volunteer study we assessed the impact of sex on different biomarkers of exposure corresponding to the three organic solvents mentioned above. Results from that study suggested that not only physiological differences between men and women but also differences due to sex hormones levels could influence the toxicokinetics of the solvents. In fact the use of hormonal contraceptive had an effect on the urinary levels of several biomarkers, suggesting that exogenous sex hormones could influence CYP2E1 enzyme activity. These experimental data were used to calibrate the toxicokinetic models developed in this study. Our results showed that it was possible to use an existing general toxicokinetic model for other compounds. In fact, most of the simulation results showed good agreement with the experimental data obtained for the studied solvents, with a percentage of model predictions that lies within the 95% confidence interval varying from 44.4 to 90%. Results pointed out that for same exposure conditions, men and women can show important differences in urinary levels of biological indicators of exposure. Moreover, when running the models by simulating industrial working conditions, these differences could be even more pronounced. A general and simple toxicokinetic model, adapted for three well-known organic solvents, allowed us to show that metabolic parameters can have an important impact on the urinary levels of the corresponding biomarkers. These observations give evidence of an interindividual variability, an aspect that should have its place in the approaches for setting limits of occupational exposure.

Absorption and disposition of the sphingosine 1-phosphate receptor modulator fingolimod (FTY720) in healthy volunteers: a case of xenobiotic biotransformation following endogenous metabolic pathways.

Fingolimod [(FTY720), Gilenya; 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol], a new drug for the treatment of relapsing multiple sclerosis, acts through its phosphate metabolite, which modulates sphingosine 1-phosphate receptors. This represents a novel mechanism of action. In the present work, the absorption and disposition of (14)C-labeled fingolimod were investigated in healthy male volunteers after a single oral dose of 4.5 mg. Total radioactivity was determined in blood, urine, and feces. Fingolimod was quantified in blood. Metabolite profiles were determined in blood and excreta, and metabolite structures were elucidated by mass spectrometry, wet-chemical methods, and comparison with reference compounds. Fingolimod was absorbed slowly but almost completely. The biotransformation of fingolimod involved three main pathways: 1) reversible phosphorylation to fingolimod phosphate [(S)-enantiomer, active principle]; 2) ω-hydroxylation at the octyl chain, catalyzed predominantly by CYP4F enzymes, followed by further oxidation to a carboxylic acid and subsequent ß-oxidation; and 3) formation of ceramide analogs by conjugation with endogenous fatty acids. This metabolism is quite unusual because it follows metabolic pathways of structurally related endogenous compounds rather than biotransformations typical for xenobiotics. The elimination of fingolimod was slow and occurred predominantly by oxidative metabolism whereas fingolimod phosphate was eliminated mainly by dephosphorylation back to fingolimod. Drug-related material was excreted mostly in the urine in the form of oxidation products.

Sensitive headspace gas chromatography analysis of free and conjugated 1-methoxy-2-propanol in urine.

Glycol ethers still continue to be a workplace hazard due to their important use on an industrial scale. Currently, chronic occupational exposures to low levels of xenobiotics become increasingly relevant. Thus, sensitive analytical methods for detecting biomarkers of exposure are of interest in the field of occupational exposure assessment. 1-Methoxy-2-propanol (1M2P) is one of the dominant glycol ethers and the unmetabolized urinary fraction has been identified to be a good biological indicator of exposure. An existing analytical method including a solid-phase extraction and derivatization before GC/FID analysis is available but presents some disadvantages. We present here an alternative method for the determination of urinary 1M2P based on the headspace gas chromatography technique. We determined the 1M2P values by the direct headspace method for 47 samples that had previously been assayed by the solid-phase extraction and derivatization gas chromatography procedure. An inter-method comparison based on a Bland-Altman analysis showed that both techniques can be used interchangeably. The alternative method showed a tenfold lower limit of detection (0.1 mg/L) as well as good accuracy and precision which were determined by several urinary 1M2P analyses carried out on a series of urine samples obtained from a human volunteer study. The within- and between-run precisions were generally about 10%, which corresponds to the usual injection variability. We observed that the differences between the results obtained with both methods are not clinically relevant in comparison to the current biological exposure index of urinary 1M2P. Accordingly, the headspace gas chromatography technique turned out to be a more sensitive, accurate, and simple method for the determination of urinary 1M2P.

[Felbamate crystalluria]. / Cristallurie de felbamate.

This report describes the case of an 11-year-old child, who presents crystalluria occurring after several years of treatment with antiepileptic felbamate (Taloxa®). The crystalline morphologies observed were very heterogeneous, long and thin needle shapped-crystals or even hairy crystals or large needle asymmetric crystals. Crystals showed an intense polarization and a strong tendency to aggregation. An infrared spectrum (KBr pellets) recorded in washed and dried urinary sediment demonstrated that these crystals are felbamate crystals. Crystal does not contain any Ca2+ and is not sensitive to pH changes suggesting that crystallization risk will not be affected by the potential association of felbamate with an inhibitor of carbonic anhydrase. After admission, creatinine level was in normal range but hematuria described by the child's mother could be symptomatic of even greater crystallization episodes and substantiate obstructive risk. A permanent good dilution of urine is the key measure to control risk of crystallization. Regular monitoring of urine specific gravity and urinary red cells by simple urine dipstick test can be proposed.

Studies on toxic oil syndrome: development of an enzyme-linked immunosorbent assay for 3-(N-phenylamino)propane-1,2-diol in human urine.

The fatty acid esters of 3-(N-phenylamino)propane-1,2-diol (PAP) are biomarkers of toxic oil batches that caused toxic oil syndrome (TOS), an intoxication that caused over 400 deaths and affected 20,000 people in Spain in 1981. PAP esters are converted into PAP by human pancreatic lipase. The in vivo biotransformation of PAP in two mouse strains generated potentially toxic metabolites. Here we report an enzyme-linked immunosorbent assay (ELISA) for PAP detection incorporating antibodies generated using PAP-hapten derivatives 1 and 2. The immunizing haptens were designed to recognize the phenylamino and hydroxymethylene moieties of the PAP structure. The antisera raised against 1-HCH showed greater affinity for free PAP, as demonstrated in competitive experiments using either 1-BSA or 2-BSA as coating antigens. The developed ELISA detects PAP at a threshold of 130 µg L(-1) and can be used over a wide range of pH and ionic strength values. The assay can be applied to human urine samples, after a simple treatment method, with good recovery according to the correlation obtained when analyzing blind spiked urine samples.

Ethnic sensitivity study of fingolimod in white and Asian subjects.

OBJECTIVE: The authors compared the pharmacokinetics and pharmacological effects of the immunomodulator fingolimod in healthy white and Asian subjects for potential ethnic differences. METHODS: White and Asian (Japanese) healthy subjects were demographically matched for sex, age and weight. Subjects received single 1.25 mg doses of fingolimod (6 ethnic pairs), 2.5 mg (7 pairs), 5 mg (6 pairs) or 5 mg/day for 7 days (6 pairs). The pharmacokinetics of fingolimod, major metabolites, peripheral blood lymphocyte counts and heart rate were characterized over 1 month after single-dose and 2 months after multiple-dose administration. RESULTS: There were no clinically relevant differences in the fingolimod dose Cmax or dose AUC relationships between Asian subjects (slopes 0.84 and 1.05) versus white subjects (slopes 1.13 and 1.26) after single-dose administration. During multiple-dose administration, there were no clinically relevant interethnic differences in fingolimod accumulation ratios (6.6 +/- 0.4 for whites, 7.0 +/- 0.7 for Asians), area under the concentration-time curve (390 +/- 73 versus 382 +/- 106 ng x h/ml), or elimination half-life (7.4 +/- 0.8 versus 7.9 +/- 2.0 days). The acute decrease in lymphocyte counts after single- and multiple-dose fingolimod were similar in the two ethnic groups. The lymphocyte recovery rate to baseline after a 5 mg single dose and 5 mg/day multiple dose was reduced by 36 and 15% in Asian subjects compared with white subjects. The transient, acute decrease in heart rate after the first dose of fingolimod and the subsequent return to baseline was similar in the two ethnic groups. CONCLUSION: There were no marked differences between healthy white and Asian subjects in fingolimod single-dose and multiple-dose pharmacokinetics, lymphocyte trafficking and heart rate responses.

Evaluation of exposure to 1-alkoxy-2-propanols and 1-(2-methoxy-1-methylethoxy)-2-propanol by the analysis of the parent compounds in urine.

Floor lacquerers' inhalation and total exposure to 1-alkoxy-2-propanols and 1-(2-methoxy-1-methylethoxy)-2-propanol (DPGME) were measured. The total exposure was biomonitored by urinalysis of free unchanged 1-alkoxy-2-propanols and DPGME. The floor lacquerers' 8-h inhalation exposures to 1-methoxy-2-propanol (PGME), 1-butoxy-2-propanol (PGBE) and DPGME were 1.9+/-1.3 (mean+/-S.D., n=15), 1.0+/-1.4ppm (n=11) and 0.2+/-0.3ppm (n=11), respectively. The gravity-corrected urinary excretions of PGME, PGBE and DPGME were 5.3+/-5.4mumol/l, 0.9+/-0.9mumol/l and 1.5+/-2.8mumol/l, respectively. A linear relationship was found between the gravity-corrected urinary excretion of PGME (R(2)=0.82), PGBE (R(2)=0.93) and DPGME (R(2)=0.93) and their preceding 8-h inhalation exposure. The correlations between the uncorrected urinary excretions and inhalation exposures to PGME, PGBE and DPGME was also calculated and found good (R(2)=0.82-0.95). The effect of work strain on the total exposure seemed to be more relevant in the exposure to hydrophilic PGME than in the exposure to more lipophilic PGBE.

Metabolism of pentaerythritol trinitrate.

The absorption, excretion, and biotransformation of 14C-labeled pentaerythritol (PE) trinitrate was studied in man. The administration of a single sublingual dose was followed by rapid absorption and extensive biotransformation. Six drug metabolites were identified. Final excretion of the drug and its metabolites was almost totally through the kidney. Low levels of unchanged drug were present in plasma and urine. PE mononitrate was the major drug metabolite in plasma and urine. Glucuronides of PE trinitrate, dinitrate, and mononitrate were identified for the first time in man. PE trinitrate glucuronide appeared in plasma rapidly and about 8% of the dose was excreted in urine. Reversible and irreversible pathways are proposed for the formation of the metabolites. The reconversion of PE trinitrate glucuronide to PE trinitrate is postulated to explain the duration of drug activity and excretion.

Increased excretion of propan-1,3-diol and 3-hydroxypropionic acid apparently caused by abnormal bacterial metabolism in the gut.

Three patients who died in infancy showed an unusual urinary organic acid pattern with excessive excretion of 3-hydroxypropionic acid but none of the other metabolites normally associated with propionyl-CoA carboxylase deficiency. Propan-1,3-diol was present in the urine in all three cases. In the two patients examined propionyl-CoA carboxylase activity was not deficient in cultured skin fibroblasts. A fourth patient, also severely ill, showed similar urinary abnormalities. Feeding a medium-chain triglyceride-rich diet to this patient increased the ratio of 3-hydroxypropionic acid to propan-1,3-diol and resulted also in the appearance of malonic acid in the urine. These abnormal metabolites disappeared on the administration of neomycin and presumably were produced by gut bacteria.