Accuracy of a Rapid Diagnostic Test for the Presence of Direct Oral Factor Xa or Thrombin Inhibitors in Urine-A Multicenter Trial.

The rapid determination of the presence of direct oral anticoagulants (DOACs) in a patient remains a major challenge in emergency medicine and for rapid medical treatment decisions. All DOACs are excreted into urine. A sensitive and specific point-of-care test has been developed to determine whether they are present in patient urine samples. This prospective multicenter study aimed to demonstrate at least 95% correct positive and negative predictive results for factor Xa and thrombin inhibitors in urine samples using DOAC Dipstick pads compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS) (NCT03182829). Nine hundred and fourteen subjects were included and 880 were evaluated per protocol (factor Xa inhibitors apixaban, edoxaban, and rivaroxaban: n = 451, thrombin inhibitor dabigatran: n = 429) at 18 centers. The sensitivity, specificity, accuracy, and predictive values and agreement between methods for determination of factor Xa inhibitors were at least noninferior to 95% with a 0.5% margin and of thrombin inhibitor superior to 97.5%. These results were compared with LC-MS/MS results in the intention-to-analyze cohort (all p < 0.05). The receiver operating curve showed c-values of 0.989 (factor Xa inhibitors) and 0.995 (thrombin inhibitor). Visual evaluation of the factor Xa and thrombin inhibitor pads was not different between centers. Qualitative determination of both types of DOACs was accurate using the DOAC Dipstick compared with using LC-MS/MS. The high predictive values may impact laboratory and clinical decision-making processes.

Pharmacokinetics, pharmacodynamics and food effect of LB30870, a novel direct thrombin inhibitor, after single oral doses in healthy men.

1. The safety, tolerability, pharmacokinetics, pharmacodynamics, and food effect of LB30870, a new selective thrombin inhibitor, were studied in 16 healthy men. 2. A double-blind, placebo-controlled single ascending dose study was done at oral doses of 5, 15, 30, 60, 120, and 240 mg under fasting conditions. An open, randomized, balanced cross-over food effect study was done at 60 mg dose. Plasma and urinary concentrations were measured up to 48 h post-dose. Coagulation and thrombin activity markers were measured at selected time points. 3. Cmax of LB30870 was at 1.3-3.0 h post-dose with a mean apparent terminal half-life (t1/2) of 2.8-4.1 h. AUC after doses above 15 mg appeared greater than dose-proportional. In fed state, AUC showed 80% reduction relative to fasting condition. 4. At doses 60 and 120 mg, peak activated partial thromboplastin time (aPTT) increased by 1.5- and 2-fold, respectively, from baseline. The aPTT and international normalized ratio (INR) were concentration-dependent, with less within-individual variability than ecarin clotting time (ECT), prothrombin time (PT), or thrombin time (TT). 5. Single oral doses of LB30870 up to 240 mg were well tolerated. The food effect must be overcome if LB30870 is to be used as an oral anti-coagulant.

Determination of dabigatran in plasma, serum, and urine samples: comparison of six methods.

BACKGROUND: Assessing the anticoagulant effect of dabigatran may be useful in certain clinical settings. When plasma sampling is not available, serum or urine samples may provide another option for dabigatran determinations. METHODS: Dabigatran was assessed in patients on treatment under real-life conditions in plasma samples by four clotting time-based assays and in plasma, serum, and urine samples by two chromogenic substrate methods. RESULTS: The concentrations of dabigatran in patients' plasma samples were not different for the Hemoclot test (106.8±89.4 ng/mL) and the ecarin clotting time (ECT, 109.5±74.5 ng/mL, p=0.58). Activated partial thromboplastin time and prothrombinase-induced clotting time showed low correlations with the other assays. Chromogenic assays measured similar concentrations as Hemoclot and ECT. For both chromogenic assays, the concentrations of dabigatran were about 70% lower in serum than in plasma samples (p<0.0001). The intra-class coefficient (ICC, Bland-Altman analysis) was strong comparing ECT, Hemoclot thrombin inhibitor (HTI) assay, and the two chromogenic assays (r=0.889-0.737). The ICC was low for comparisons of the chromogenic assays of serum vs. plasma values (ICC, 0.15 and 0.66). The ICC for the determination of dabigatran in urine samples by the two chromogenic assays (5641.6±4319.7 and 4730.0±3770.2 ng/mL) was 0.737. CONCLUSIONS: ECT, HTI, and chromogenic assays can be used to determine dabigatran in plasma samples from patients under real-life conditions. Chromogenic assays require further improvement to reliably measure dabigatran in serum samples. Dabigatran concentrations in urine samples can also be determined quantitatively.

Heparin-mediated fluorescence anisotropy assay of antithrombin based on polyethyleneimine capped Mn-doped ZnS quantum dots.

We presented a homogeneous heparin-mediated fluorescence anisotropy (FA) assay of antithrombin (AT) based on long-lived luminescent polyethyleneimine capped Mn-doped ZnS (PEI-Mn-ZnS) QDs. The PEI-Mn-ZnS QDs with long lifetime luminescence at 585 nm displayed a very low background of FA value, which was very helpful for FA assaying of large molecules. The medium heparin was crucial for AT determination, and different heparin amounts resulted in different linear range of detection and sensitivity. For example, the limit of detection (LOD) of 0.9 nM AT with a detection linear range from 8.6 nM to 21.5 nM was found when the heparin concentration was 75 µM. The proposed method also exhibited high selectivity over the coexisting or related proteins such as human serum albumin and thrombin.

Pharmacokinetics and pharmacology of hirulog-like peptide.

Hirulog-like peptide (HLP), a new thrombin peptide inhibitor, effectively reduces neointimal formation or restenosis in rat and rabbit vascular injury models. The present study investigated the pharmacokinetics and pharmacology of HLP in Sprague-Dawley (SD) rats. The input response of HLP in rats was studied using radioisotopic tracing method. Male SD rats were intravenously injected with a single dose of I-HLP (3.2, 6.4, or 12.8 mg/kg) for pharmacokinetic analysis. The concentration-time curve of I-HLP following bolus injection fitted a 3-compartment model. The half-life of HLP in rats was between 25 and 31 min following 3.2 to 12.8 mg/kg of bolus injection. Radioactivity of I-HLP was detected in all tested tissues and was most abundant in kidneys or stomachs. Blood pressure, respiratory frequency, and heart rates were not significantly altered during continuous intravenous infusion with saline or 1.6 to 3.2 mg/kg/h of HLP for 4 h. Bleeding time and activated partial thromboplastin time were significantly prolonged in rats infused with HLP compared to vehicle. ADP-induced platelet aggregation was significantly reduced in the HLP-treated groups compared with controls. The results suggest that HLP possesses first-order kinetic characteristics. HLP is secreted mainly through kidneys. Beside its anticoagulant activity, no other adverse effect was detected in SD rats receiving HLP.

Determination of ximelagatran, an oral direct thrombin inhibitor, its active metabolite melagatran, and the intermediate metabolites, in biological samples by liquid chromatography-mass spectrometry.

Analytical methods for the determination of ximelagatran, an oral direct thrombin inhibitor, its active metabolite melagatran, and intermediate metabolites, melagatran hydroxyamidine and melagatran ethyl ester, in biological samples by liquid chromatography (LC) positive electrospray ionization mass spectrometry (MS) using selected reaction monitoring are described. Isolation from human plasma was achieved by solid-phase extraction on octylsilica. Analytes and isotope-labelled internal standards were separated by LC utilising a C(18) analytical column and a mobile phase comprising acetonitrile-4 mmol/l ammonium acetate (35:65, v/v) containing 0.1% formic acid, at a flow-rate of 0.75 ml/min. Absolute recovery was approximately 80% for ximelagatran, approximately 60% for melagatran ethyl ester and >90% for melagatran and melagatran hydroxyamidine. Limit of quantification was 10 nmol/l, with a relative standard deviation <20% for each analyte and <5% above 100 nmol/l. Procedures for determination of these analytes in human urine and breast milk, plus whole blood from rat and mouse are also described.

Quantitation of an orally available thrombin inhibitor in rat, monkey and human plasma and in human urine by high-performance liquid chromatography and fluorescent post-column derivatization of arginine.

An assay for the quantification of plasma and urine levels of CVS 1123, an orally bioavailable thrombin inhibitor, and its desmethyl form. CVS 738, was developed to support clinical and toxicology studies. This assay uses solid-phase extraction, reversed-phase HPLC separation, and post-column fluorescent derivatization with ninhydrin. An internal standard is added to correct for recovery. In aqueous solution, the arginine aldehyde structures of CVS 1123 and CVS 738 exist in multiple forms which can be separated under standard reversed-phase HPLC conditions. HPLC conditions were optimized to give rapid interconversion of the forms on the separation time scale, and consequently a single chromatographic peak. Extraction conditions were modified for quantitative extraction of drug compounds from large volumes of human plasma. The assay was shown to be accurate and precise, with a quantification limit of 17 ng CVS 1123/ml human plasma.

Metabolism of the anticoagulant peptide, MDL 28,050, in rats.

Rats were each administered a 9 mg/kg iv bolus dose of a 3H-labeled decapeptide anticoagulant, MDL 28,050. Tritium was eliminated rapidly with approximately 50% of the dose recovered in urine within the first 6 hr. Renal excretion accounted for 68% of the dose, whereas fecal excretion accounted for 16% of the dose. Continuous flow fast atom bombardment mass spectrometry was used to identify the major urinary metabolites of MDL 28,050. Trace amounts of parent drug were found, and other biotransformation products indicated that hydrolysis had occurred at four peptide bonds. Two initial sites of hydrolysis were identified as 4I-5P and 6E-7E, which resulted in the peptide fragments Suc-Y-E-P-I-OH + P-E-E-A-Cha-E-OH and Suc-Y-E-P-I-P-E-OH + E-A-Cha-E-OH, respectively. Further metabolism of these fragments resulted in the N-terminal pentapeptide and the C-terminal dipeptide.

[Protein catabolism and tourniquet shock: the role of proteolytic enzymes]. / Proteinkatabolismus und Tourniquet-Schock: Rolle proteolytischer Enzyme.

In the plasma and/or serum ultrafiltrates of a 20-year-old patient with tourniquet shock and post-traumatic acute renal failure it was possible to identify free proteolytic activity during the oligoanuric phase. Plasma alpha 2-macroglobulin values were significantly lowered, whereas the plasma concentrations of antithrombin III were unchanged. alpha 1-Antitrypsin values, however, were markedly enhanced. In contrast, urinary excretion of alpha 1-antitrypsin and antithrombin III were enhanced during the oligoanuric phase. Addition of kallikrein and/or trypsin resulted in strong inhibition of urinary proteolytic activity. These effects were not seen during the polyuric and recovery phase. From our results it can be concluded that proteolytic enzymes may be involved in protein catabolism of patients with tourniquet shock and hypercatabolic acute renal failure.

Unilateral renal vein thrombosis and nephrotic syndrome. Report of a case with protein selectivity and antithrombin III clearance studies.

A case of the nephrotic syndrome with unilateral renal vein thrombosis is reported. The patient, an 18 year old man, presented with a six month history of edema and the recent development of a left-sided varicocele. An enlarged left kidney and a thrombus in the left renal vein were demonstrated roentgenographically. A biopsy specimen of the right kidney was interpreted as membranous glomerulonephritis. Selective renal function studies showed nearly identical creatinine excretion, and similar total protein excretion and protein selectivity from each kidney. Thus, the thrombus in the left renal vein did not influence glomerular filtration rate or quantitative or qualitative protein excretion. A high urinary output and a decreased serum level of antithrombin III were measured. These findings suggest a mechanism to explain the increased thrombotic tendency seen in this and other patients with the nephrotic syndrome.