Analytical methods urinary

After oral administration of 400 mg of rifaximin to fasted healthy volunteers blood drug concentration was found to be lower than the detection limit of the analytical method (i.e. 2.5 ng/ml) in half of them [102]. In the remaining subjects very low amounts were detected at some of the time intervals during the first 4 h after intake. Along the same lines, the urinary concentrations of the drug were very low and often undetectable. The effect of food on the absorption of the antibiotic was also evaluated [34] and a significant, albeit not clinically relevant, increase of bioavailabity was observed after a high-fat breakfast (table 5). 

Determination in Biological Fluids and Tissues All the advances in pharmacokinetics and drug metabolism described in Sections 7 and 8 would not have been possible without the availability of the proper analytical methods. The following is a tabulation of publications in this field, most of which have already been discussed in Section 5. It should be mentioned that a few publications talk about aspirin blood levels, but really mean salicylate levels. The following tabulation covers only those papers where aspirin was differentiated from other salicylates by chromatography or other means. It seems that the "workhorse" for serum salicylate levels is still the colorimetric (ferric-nitrate) method of Brodie, Udenfriend and Coburn153 published in 1944, or modifications thereof. Simplified versions (cf. 206) may lead to erroneous results under certain conditions.207 The method is also applicable for urinary metabolites after proper hydrolysis (cf. 208). For other methods restricted to salicylic acid, see Section 5.61. 

Weanling female rats were used as the test model in these studies. They were housed individually (10 rats/diet) and offered diet and deionized water ad libitum for 5 months. Apparent calcium and phosphorus absorption and urinary Ca and P losses were measured on collections made the last five days each month. Urine volume and pH values were also recorded. Other data (growth response, serum Ca and P levels, femur mineral composition, femur strength and density, and femur histology) were obtained at the end of the 5-month feeding study. Details of this and the analytical methods used are presented elsewhere (8). All data were subjected to appropriate statistical analyses. 

However, urine has no great relevance in quantitative analysis because the analyte concentrations vary depending on the dose, means of administration, physiological status (urinary pH, sex, age, weight, etc.), the time lag between intake and analysis, the addition of adulterants. So the analytical data of urine may only indicate the presence of a substance up to a defined cutoff point the monitoring window (time interval in which a substance can be detected by ordinary analytical methods) varies from a few days for cocaine, amphetamine, methoxyamphetamine to 2-3 weeks for cannabinoids. 

Analytical methods have been reported for unchanged agent and six of the urinary excretion products described above. These are TDG, TDGO, the bis A-acetylcysteine conjugate (1), two 3-lyase metabolites (2) and (3), and the guanine adduct (6). These methods have been applied to animal and/or human exposures to sulfur mustard. 

The improvement in analytical methods has shown the importance of quantitative determination of more than one urinary metabolite which, alone, does not always reveal a metabolic abnormality. 

Analytical methods are available to measure mercury in blood, urine, tissue, hair, and breast milk [11]. Biological monitoring of mercury is very useful for assessing exposure as well as risk for health effects [17], but comphcated by the fact that both organic and inorganic forms of mercury occur in the body and can be identified in blood and urine. Mercury concentration in individuals who are not occupationally exposed, and whose fish intake is moderate or low, varies between 0.1 and 7 pg/L. The lower values are found in urine and the higher in blood. Urinary mercury is thought... 

Regardless of whether the data are analysed by a compartmental or non-compartmental method, the duration of blood sampling and the limit of quantification of the analytical method used to measure the drug concentration are important features of the pharmacokinetic study. The MRT, after an intravenous bolus dose of a drug can be estimated from either plasma drug concentration or urinary excretion data (Rowland Tozer, 1989). 

Because NDMA is metabolized almost quantitatively in humans (Spiegelhalder 1984), determination of this compound in human urine needs an extremely sensitive technique (Garland et al. 1986). The urinary excretion of NDMA has been correlated with the concentration of N02 in air, suggesting that ambient air may play a role in the exposure of people to nitrosoamines (Garland et al. 1986). There is a paucity of data on the analytical methods for the determination of N-nitrosodimethylamine in human urine. 

Aprea C, Sciarra G, Lunghini L. Analytical method for the determination of urinary alkylpho-sphates in subjects occupationally exposed to organophosphorus pesticides and in the general population. J Anal Toxicol 1996 20 559-63. 

Aprea C, Betta A, Catenacci G, Lotti A, Magnaghi S, Barisano A, et al. Reference values of urinary 3,5,6-trichloro-2-pyridinol in the Italian population - vahdation of analytical method and pre-hminary results (multicentric study). J AOAC Int 1999 82 305-12. 

Recent analytical methods have made it possible to do routine determinations of urinary lactose quite readily F. V. Flynn, C. Harper and P. De Mayo, Lancet, 265, 698 (1953). 

Sensitivity is closely related to the specificity and precision of a method. As an extremely important aspect of any method for plasma steroids, and of many for urinary steroids, it has been much discussed. In terms of the best levels of signal-to-noise ratio obtained with pure substances under ideal conditions, the mass spectrometer attached directly to a good GLC column is probably the most sensitive analytical method currently available. In terms of steroids in natural sources the most sensitive methods at present established are those using the isotopic-displacement (protein-binding) technique (0.1-0.5 ng) and electron-... 

B. A. G., Development, validation and characterization of an analytical method for the quantification of hydrolysable urinary metabolites and plasma protein adducts of 2,4-and 2,6-toluene diisocyanate, 1, 5-naphthalene diisocyanate and 4,4 -methylenediphenyl diisocyanate. Biomarkers, 8, 204-217, 2003. 

In order to assess the overall performance of toxicological laboratories in the European Community (EC) and the applicability of analytical methods a long-term interlaboratory survey of the quality of (total) urinary arsenic and thallium was performed with twelve laboratories representing ten member countries (de Zeeuw et al., 1987). The results of the individual laboratories as well as the interlaboratory data showed in general an acceptable performance for bias and precision. 

Vanadium concentrations in blood, serum or urine are used as a biological indicator of exposure to vanadium. Urine and serum are the specimens with widest application and greatest practicability for monitoring human exposure to vanadium compounds, but urine is preferred as an indicator medium. Blood vanadium appears to be a less sensitive indicator than urinary vanadium, partly because the differences in concentrations are hardly appreciable at low levels of exposure with the analytical methods available (Alessio et al., 1988). 

Aprea, C Betta, A., Cacenacci, G, Lotii, A, Magnaghi, S., Barisano, A, Pas.sini, V., Pavan, L, Sciarra, G, Vitalone. V., and Mitioia, C. (1999), Reference value.s of urinary 3,.5,6-trictiloro-2-pyridinol in the Italian population—Validation of analytical method and preliminary results (muiticentric study), J. AOACfni. 82(2). 305-312. 

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