Simultaneous determination of amitraz, chlordimeform, formetanate and their main metabolites in human urine by high performance liquid chromatography-tandem mass spectrometry.

A rapid, simple and reliable high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for simultaneous determination of amitraz, chlordimeform, formetanate and their main metabolites, N-(2,4-dimethylphenyl)-N-methyl-formamidine (DMPF), 2,4-dimethylformamidine (DMF), 2,4-dimethylaniline (DMA), 4-chloro-2-methylaniline and 3-hydroxyacetanilide in human urine. The urine samples were mixed with buffer solutions (pH 8) and subsequently cleaned up by solid supported liquid/liquid extraction (SLE). The target analytes were efficiently separated with a Waters Atlantis T3 column (150mm×4.6mm, 5µm), ionized with electrospray ion source in positive mode, and quantitatively determined by tandem mass spectrometry in the multiple reaction monitoring (MRM) mode. In order to minimize matrix effects, the matrix-matched calibration curves of eight analytes were adopted with correlation coefficients (R2) above 0.99. The method were further validated by determining the limits of detection (LODs, 0.3-0.6ng/mL), the limits of quantitation (LOQs, 1.0-2.0ng/mL) and recoveries (89.1%-108.4%) with intra-day and inter-day relative standard deviation (RSD, <11%). The established method was applied and demonstrated in a real case by assaying a urine sample from a female poisoned by formetanate. The achieved results proved this method to be rapid, sensitive and accurate for simultaneous quantitation of eight analytes in human urine for intended forensic cases of human poisoning.

Pharmacokinetic and pharmacodynamics of xylazine administered to exercised thoroughbred horses.

There is limited data describing xylazine serum concentrations in the horse and no reports of concentrations beyond 24 hours. The primary goal of the study reported here was to update the pharmacokinetics of xylazine following intravenous (IV) administration in order to assess the applicability of current regulatory recommendations. Pharmacodynamic parameters were determined using PK-PD modeling. Sixteen exercised adult Thoroughbred horses received a single IV dose of 200 mg of xylazine. Blood and urine samples were collected at time 0 and at various times for up to 96 hours and analyzed using liquid chromatography tandem mass spectrometry. Xylazine serum concentrations were best fit by a 3-compartment model. Mean ± SEM systemic clearance, volume of distribution at steady state, beta half-life and gamma half-life were 12.7 ± 0.735 mL/min/kg, 0.660 ± 0.053 L/kg, 2.79 ± 0.105 hours and 26.0 ± 1.9, respectively. Immediately following administration, horses appeared sedate as noted by a decrease in chin-to-ground distance, decreased locomotion and decreased heart rate (HR). Sedation lasted approximately 45 minutes. Glucose concentrations were elevated for 1-hour post administration. The EC50 (IC50) was 636.1, 702.2, 314.1 and 325.7 ng/mL for HR, atrioventricular block, chin-to-ground distance and glucose concentrations, respectively. The Emax (Imax) was 27.3 beats per minute, 47.5%, 42.4 cm and 0.28 mg/dL for HR, atrioventricular block, chin-to-ground distance and glucose concentrations, respectively. Pharmacokinetic parameters differ from previous reports and a prolonged detection time suggests that an extended withdrawal time, beyond current regulatory recommendations, is warranted to avoid inadvertent positive regulatory findings in performance horses. Copyright © 2016 John Wiley & Sons, Ltd.

A HPLC-MS method to detect and quantify guanfacine in urine.

BACKGROUND: Guanfacine, an α2-adrenergic α2A)agonist long indicated to treat hypertension, is now being used to treat attention deficit-hyperactivity disorder (ADHD) in adolescents. This new therapeutic use may require urine testing to document compliance or abuse. A simple rapid high pressure liquid chromatography-mass spectrometry (HPLC-MS) method to detect and quantify guanfacine in urine following therapeutic administration is presented. METHODS: Guanfacine and protriptyline internal standard were extracted from alkalinized urine with ethyl acetate. The organic layer was evaporated, reconstituted with mobile phase and analyzed on a YMC Basic S-5 micron, 2.0 × 150 mm HPLC column connected to an MS detector operated in positive electrospray ionization mode with selected ion resonance. Elution times were <5 min. RESULTS: The analytical measurement range for guanfacine was 20-2000 ng/mL. The limit of detection and quantitation were 5 ng/mL and 20 ng/mL, respectively. Precision as %CV was <15% at 40, 100 and 500 ng/mL (n=6). Percentage recovery using the same concentrations was >89%. Interference with drugs and biological constituents was assessed; no interferences were noted. Analysis of 100 random post-diagnostic urine specimens yielded 11 guanfacine positive results with concentrations ranging from 11 to 6390 ng/mL. CONCLUSIONS: This HPLC-MS method provides a simple and rapid method for the routine detection and quantitation of guanfacine in urine specimens.