Pharmacokinetics of the low molecular weight heparin dalteparin in cats

Effects of a single subcutaneous dose of enoxaparin on veterinary viscoelastic coagulation monitor variables in healthy cats: Double blind, placebo controlled cross-over trial

BACKGROUND

Cats placed on anticoagulant medication require frequent monitoring. The veterinary viscoelastic coagulation monitor (VCM-Vet) could provide a convenient and cost-effective monitoring, enabling therapeutic decision making.

HYPOTHESIS/OBJECTIVES

Enoxaparin will lead to changes in VCM-Vet variables and these will correlate with antiXa activity.

ANIMALS

Twenty-one healthy cats.

METHODS

Cats were randomized to receive either enoxaparin (1 mg/kg) subcutaneously or 0.9% NaCl (equal volume) and crossed over with a 7-day washout period. The investigators were blinded to group allocation until data analysis. Jugular blood samples were drawn at time 0, and 2, 4, and 8 hours after injection for VCM-Vet analysis within 2 min of collection. Citrated plasma was frozen at -80°C for antiXa activity analysis. A Generalized Linear Model was completed to assess changes between baseline measurements and all time points.

RESULTS

Significant differences between the enoxaparin-treated cats and controls at for T0h and T2h were found and presented as mean ± SD for clotting time (enoxaparin, 593.4 ± 78.0 s; control, 448.5 ± 50.3 s, P < .001), clot formation time (enoxaparin, 183.1 ± 41.7 s; control, 155.4 ± 28.0 s, P = .001), and alpha angle (enoxaparin, 52.4 ± 6.1°; control, 56.9 ± 3.7 s, P = .003). AntiXa activity was significantly different between T0 and all other timepoints for the enoxaparin group (P < .001). There was no correlation between changes in clotting time and antiXa activity.

CONCLUSIONS AND CLINICAL IMPORTANCE

The VCM-Vet detects a difference at 2 hours after single-dose enoxaparin administration and it can be useful for anticoagulant therapy monitoring in cats.

Pharmacokinetics and Pharmacodynamics of a Depolymerized Glycosaminoglycan from Holothuria fuscopunctata, a Novel Anticoagulant Candidate, in Rats by Bioanalytical Methods

dHG-5 (Mw 5.3 kD) is a depolymerized glycosaminoglycan from sea cucumber Holothuria fuscopunctata. As a selective inhibitor of intrinsic Xase (iXase), preclinical study showed it was a promising anticoagulant candidate without obvious bleeding risk. In this work, two bioanalytical methods based on the anti-iXase and activated partial thromboplastin time (APTT) prolongation activities were established and validated to determine dHG-5 concentrations in plasma and urine samples. After single subcutaneous administration of dHG-5 at 5, 9, and 16.2 mg/kg to rats, the time to peak concentration (Tmax) was at about 1 h, and the peak concentration (Cmax) was 2.70, 6.50, and 10.11 μg/mL, respectively. The plasma elimination half-life(T1/2β) was also about 1 h and dHG-5 could be almost completely absorbed after s.c. administration. Additionally, the pharmacodynamics of dHG-5 was positively correlated with its pharmacokinetics, as determined by rat plasma APTT and anti-iXase method, respectively. dHG-5 was mainly excreted by urine as the unchanged parent drug and about 60% was excreted within 48 h. The results suggested that dHG-5 could be almost completely absorbed after subcutaneous injection and the pharmacokinetics of dHG-5 are predictable. Studying pharmacokinetics of dHG-5 could provide valuable information for future clinical studies.

Therapeutic monitoring of rivaroxaban in dogs using thromboelastography and prothrombin time

BACKGROUND

The chromogenic anti-Xa assay, the gold standard for monitoring the anti-Xa effect of rivaroxaban, is not available as a cage-side diagnostic test for use in a clinical setting.

HYPOTHESIS/OBJECTIVES

To evaluate clinical modalities for measuring the anticoagulant effects of rivaroxaban using a point-of-care prothrombin time (PT) and thromboelastography (TEG).

ANIMALS

Six healthy Beagle dogs.

METHODS

Prospective, experimental study. Four different doses of rivaroxaban (0.5, 1, 2, and 4 mg/kg) were administered PO to dogs. Single PO and 3 consecutive dosing regimens also were assessed. Plasma rivaroxaban concentration was determined using a chromogenic anti-Xa assay, point-of-care PT, and TEG analysis with 4 activators (RapidTEG, 1 : 100 tissue factor [TF100], 1 : 3700 tissue factor [TF3700], and kaolin), and results were compared. Spearman correlation coefficients were calculated between ratios (peak to baseline PT; peak reaction time [R] of TEG to baseline [R] of TEG) and anti-Xa concentration.

RESULTS

Anti-Xa concentration had a significant correlation with point-of-care PT (R = 0.82, P < .001) and RapidTEG-TEG, TF100-TEG, and TF3700-TEG (R = 0.76, P < .001; R = 0.82, P < .001; and R = 0.83, P < .001, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Overall, a 1.5-1.9 × delay in PT and R values of TEG 3 hours after rivaroxaban administration is required to achieve therapeutic anti-Xa concentrations of rivaroxaban in canine plasma. The R values of TEG, specifically using tissue factors (RapidTEG, TF100, TF3700) and point-of-care PT for rivaroxaban can be used practically for therapeutic monitoring of rivaroxaban in dogs.

Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 4-Refining and monitoring antithrombotic therapies

OBJECTIVES

To systematically review the evidence for therapeutic monitoring of antithrombotic drugs in small animals, develop guidelines regarding antithrombotic monitoring, and identify knowledge gaps in the field.

DESIGN

First, a standardized, systematic literature review was conducted to address predefined PICO (Population/Patient, Intervention, Control, Outcome) questions, with categorization of relevant articles according to level of evidence and quality. Preliminary guidelines were developed by PICO worksheet authors and the domain chair. Thereafter, a Delphi-style survey was used to develop consensus on guidelines regarding therapeutic monitoring of antithrombotics in dogs and cats.

SETTING

Academic and referral veterinary medical centers.

RESULTS

PICO questions regarding the utility of therapeutic monitoring were developed for 6 different antithrombotic drugs or drug classes, including aspirin, clopidogrel, warfarin, unfractionated heparin, the low molecular weight heparins, and rivaroxaban, The majority of the literature pertaining to therapeutic monitoring of antithrombotic drugs was either performed in experimental animal models of disease or involved studies of drug pharmacokinetics and pharmacodynamics in healthy laboratory animals. There was a paucity of high level of evidence studies directly addressing the PICO questions, which limited the strength of recommendations that could be provided. The final guidelines recommend that therapeutic monitoring should be performed when using warfarin or unfractionated heparin in dogs and cats at risk of thrombosis. There is insufficient evidence to make strong recommendations for therapeutic monitoring of aspirin or low molecular weight heparin in dogs and cats at this time.

CONCLUSIONS

As in other CURATIVE domains, significant knowledge gaps were highlighted, indicating the need for substantial additional research in this field. Ongoing investigation of the role of therapeutic monitoring of antithrombotic therapies will undoubtedly facilitate improved outcomes for dogs and cats at risk of thrombosis.

American College of Veterinary Emergency and Critical Care (ACVECC) Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines: Small animal

OBJECTIVES

To systematically review available evidence and establish guidelines related to the risk of developing thrombosis and the management of small animals with antithrombotics.

DESIGN

Standardized, systematic evaluation of the literature (identified by searching Medline via PubMed and CAB abstracts) was carried out in 5 domains (Defining populations at risk; Defining rational therapeutic use; Defining evidence-based protocols; Refining and monitoring antithrombotic therapies; and Discontinuing antithrombotic therapies). Evidence evaluation was carried out using Population, Intervention, Comparison, Outcome generated within each domain questions to address specific aims. This was followed by categorization of relevant articles according to level of evidence and quality (Good, Fair, or Poor). Synthesis of these data led to the development of a series of statements. Consensus on the final guidelines was achieved via Delphi-style surveys. Draft recommendations were presented at 2 international veterinary conferences and made available for community assessment, review, and comment prior to final revisions and publication.

SETTINGS

Academic and referral veterinary medical centers.

RESULTS

Over 500 studies were reviewed in detail. Worksheets from all 5 domains generated 59 statements with 83 guideline recommendations that were refined during 3 rounds of Delphi surveys. A high degree of consensus was reached across all guideline recommendations.

CONCLUSIONS

Overall, systematic evidence evaluations yielded more than 80 recommendations for the treatment of small animals with or at risk of developing thrombosis. Numerous significant knowledge gaps were highlighted by the evidence reviews undertaken, indicating the need for substantial additional research in this field.

Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 3-Defining antithrombotic protocols

OBJECTIVES

To systematically examine the evidence for use of a specific protocol (dose, frequency, route) of selected antithrombotic drugs, in comparisons to no therapy or to other antithrombotic therapies, to reduce the risk of complications or improve outcomes in dogs and cats at risk for thrombosis.

DESIGN

Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence (LOE) and quality (Good, Fair, or Poor), and development of consensus on conclusions via a Delphi-style survey for application of the concepts to clinical practice.

SETTINGS

Academic and referral veterinary medical centers.

RESULTS

Databases searched included Medline via PubMed and CAB abstracts. Eight different antithrombotic drugs were investigated using a standardized Patient, Intervention, Comparison, Outcome (PICO) question format both for dogs and cats, including aspirin, clopidogrel, warfarin, unfractionated heparin (UFH), dalteparin, enoxaparin, fondaparinux, and rivaroxaban, generating a total of 16 worksheets. Most studies identified were experimental controlled laboratory studies in companion animals (LOE 3) with only four randomized controlled clinical trials in companion animals (LOE 1).

CONCLUSIONS

Overall, evidence-based recommendations concerning specific protocols could not be formulated for most antithrombotic drugs evaluated, either because of the wide range of dosage reported (eg, aspirin in dogs) or the lack of evidence in the current literature. However, clopidogrel administration in dogs and cats at risk of arterial thrombosis, notably in cats at risk of cardiogenic thromboembolism, is supported by the literature, and specific protocols were recommended. Comparably, aspirin should not be used as a sole antithrombotic in cats with cardiomyopathy. Using the available safety profile information contained in the literature, the panel reached consensus on suggested dosage schemes for most antithrombotics. Significant knowledge gaps were highlighted, which will hopefully drive novel research.

Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 2-Defining rational therapeutic usage

OBJECTIVES

To systematically review available evidence to determine when small animals at risk of thrombosis should be treated with antiplatelet agents and anticoagulants, which antiplatelet and anticoagulant agents are most effective, and when multimodal therapy is indicated.

DESIGN

Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence (LOE) and quality (Good, Fair, or Poor), and development of consensus on conclusions via a Delphi-style survey for application of the concepts to clinical practice. Draft recommendations were presented at 2 international veterinary conferences and made available for community assessment, review, and comment prior to final revisions and publication.

SETTINGS

Academic and referral veterinary medical centers.

RESULTS

Databases searched included Medline via PubMed and CAB abstracts. Twelve Population Intervention Comparison Outcome questions were devised and generated corresponding worksheets investigating indications for use of antithrombotic drugs in small animals. Seventy-eight studies were reviewed in detail. Most studies assessed were experimentally controlled laboratory studies in companion animals (56 LOE 3) with smaller numbers of LOE 2 (1), LOE 4 (5), LOE 5 (6), and LOE 6 (4) studies assessed. Only 5 randomized controlled clinical trials were identified (LOE 1, Good-Fair). The 12 worksheets generated 21 guidelines with 17 guideline statements that were refined during 3 rounds of Delphi surveys. A high degree of consensus was reached across all guideline recommendations during the Delphi process.

CONCLUSIONS

Overall, systematic evidence evaluations generated 2 strong recommendations, 19 weak recommendations (formulated as suggestions), 9 situations where the evidence was insufficient to make strong recommendations, and 8 situations where no relevant evidence was retrieved to aid guideline generation. Numerous significant knowledge gaps were highlighted by the evidence reviews undertaken, indicating the need for substantial additional research in this field.