Development of UHPLC-MS/MS methods to quantify 25 antihypertensive drugs in serum in a cohort of patients treated for hypertension.

We developed three ultra-high pressure liquid chromatography coupled to mass spectrometry detection (UHPLC-MS/MS) methods to quantify 25 antihypertensive drugs in serum samples. Patient-reported drug lists were collected, and drug concentrations were analysed in samples from 547 patients, half with uncontrolled hypertension, and all treated with ≥ 2 antihypertensive drugs. For sample preparation, serum was mixed with deuterated internal standards and acetonitrile and precipitated. Aliquots of the supernatant were injected on UHPLC-MSMS with a C18 reversed phase column. The mobile phase was 0.1 % HCOOH (formic acid) in water and 0.1 % HCOOH in acetonitrile (except in methanol for spironolactone/canrenone) at a flow rate of 0.4 mL/min. The calibrators and internal controls were prepared in Autonorm™. The calibration ranges were wide, and the models were linear or quadratic with squared correlation coefficients ≥ 0.97. The limits of detection and quantification, specificity, carry-over, and matrix effects were acceptable. The accuracy of the internal controls was in the range 85-121 %, and the intermediate precision for all drugs was 4-28 %. The patient-reported antihypertensive drug use and the detected serum drug concentrations were in accordance with that most frequently prescribed nationally. The percent non-detectable level was 5-10 % for bendroflumethiazide, doxazosin, nifedipine, and ramipril. Often the drug dose chosen was lower than the recommended maximum daily dose. We report the maximum (Cmax) and minimum (Cmin) drug concentrations after drug intake. The inter-individual pharmacokinetic variability at Cmin was 18-fold for hydrochlorothiazide, 22-fold for losartan carboxyl acid, 26-fold for amlodipine, 44-fold for candesartan, and 50-fold for valsartan. Our methods are suitable for measuring antihypertensive drugs in patient serum for therapy control.

A comparison of an optimized automated sample preparation of PEth in blood pretreated by freezing versus manual preparation in whole blood, analyzing by UHPLC - MS/MS.

A robust and simple high-throughput automatic sample preparation in a 96-well plate format for quantification of PEth16:0/18:1 with UHPLC-MS/MS in pre-treated frozen blood samples has been simplified as well as optimised regarding liquid handling parameters. To keep the air cushion in the pipetting step as small as possible, 300 µl pipette tips were used instead of 1000 µl tips for pipetting the minimum volume of 2-propanol required for the sample preparation. The 96-well plate was mixed vigorously to acquire a good reproducibility of the PEth results. A 96-wellplate with a well volume of 2.0 ml was used to eliminate cross contamination between the wells, and the calibration curve covered a concentration range from 0.03 to 5 µmol/l. The method was sensitive, and the limit of quantification was 0.005 µmol/l for PEth. The matrix effect in whole blood was small and corrected to 106% by using an isotope-labelled internal standard. There was no carry-over observed after the highest standard 5 µmol/l. The intermediate precision and accuracy were, respectively, less than 9% and 101% when using both the automated and manual sample preparation method. 19 external controls were analysed from an Equalis proficiency testing program for a period of 16 months, and our results were always within 79% of the assigned value. 114 samples were analysed by manual and automatic sample preparation with UHPLC-MS/MS in respectively whole blood and pre-treated frozen blood samples. The mean percentage difference of these measurements between the two methods was calculated in accordance with (Bland & Altman) to be (-4.8 ± 5.6) %.

Fomepizole dosing during continuous renal replacement therapy - an observational study.

BACKGROUND: Fomepizole is the preferred antidote for treatment of methanol and ethylene glycol poisoning, acting by inhibiting the formation of the toxic metabolites. Although very effective, the price is high and the availability is limited. Its availability is further challenged in situations with mass poisonings. Therefore, a 50% reduced maintenance dose for fomepizole during continuous renal replacement therapy (CRRT) was suggested in 2016, based on pharmacokinetic data only. Our aim was to study whether this new dosing for fomepizole during CRRT gave plasma concentrations above the required 10 µmol/L. Secondly, we wanted to study the elimination kinetics of fomepizole during CRRT, which has never been studied before. METHODS: Prospective observational study of adult patients treated with fomepizole and CRRT. We collected samples from arterial line (pre-filter) = plasma concentration, post-filter and dialysate for fomepizole measurements. Fomepizole was measured using high-pressure liquid chromatography with a reverse phase column. RESULTS: Ten patients were included in the study. Seven were treated with continuous veno-venous hemodialysis (CVVHD) and three with continuous veno-venous hemodiafiltration (CVVHDF). Ninety-eight percent of the plasma samples were above the minimum plasma concentration of 10 µmol/L. Fomepizole was removed during CRRT with a median saturation/sieving coefficient of 0.85 and dialysis clearance of 28 mL/min. CONCLUSION: Fomepizole was eliminated during CCRT. The new dosing recommendations for fomepizole and CRRT appeared safe, by maintaining the plasma concentration above the minimum value of 10 µmol/L. Based on these data, the fomepizole maintenance dose during CRRT could be reduced to half as compared to intermittent hemodialysis.

Beta-hydroxybutyrate and pyroglutamate can be included in a rapid GC-MS screening method for differential diagnosis of metabolic acidosis.

A rapid gas chromatographic mass spectrometric method for measuring anions associated with acute anion gap metabolic acidosis is described. The method is an extension of a previous method. The method quantifies glycolic acid, beta-hydroxybutyric acid with good linearity and pyroglutamic acid with a reproducible curvature relation between 1 and 20 mmol/L and can help the clinician distinguish effectively between ethylene glycol poisoning, alcoholic and diabetic ketoacidosis and cysteine deficiency so early that it will have clinical consequences.

Levels and temporal trends (1983-2003) of polybrominated diphenyl ethers and hexabromocyclododecanes in seabird eggs from north Norway.

The present study assessed temporal trends (1983-2003) of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in eggs of herring gulls (Larus argentatus), Atlantic puffins (Fratercula arctica), and black-legged kittiwakes (Rissa tridactyla) in North Norway. Generally, PBDE concentrations increased between 1983 and 1993 and then leveled out, although species-specific trends were reported. Levels of alpha-HBCD increased in all species throughout the 20-year period. Levels of nona-BDEs and BDE 209 ranged from nondetectable to parts per billion. Nevertheless, highly variable procedural blanks were reported for the nona-BDEs and BDE 209, which clearly illustrates the importance of including blanks repeatedly during determination of these compounds.