High-dose aspirin in dogs increases vascular resistance with limited additional anti-platelet effect when combined with potent P2Y12 inhibition

The use of high-dose immunoglobulin M-enriched human immunoglobulin in dogs with immune-mediated hemolytic anemia

BACKGROUND

The IV use of human immunoglobulin (hIVIG) in dogs with primary immune-mediated hemolytic anemia (IMHA) has been described previously, but herein we describe the use of high-dose IgM-enriched hIVIG (Pentaglobin).

HYPOTHESIS/OBJECTIVES

Dogs treated with high-dose Pentaglobin will experience shorter time to remission and hospital discharge and have decreased transfusion requirements compared to dogs receiving standard treatment alone.

ANIMALS

Fourteen client-owned dogs diagnosed with primary IMHA at specialist referral hospitals in the United Kingdom.

METHODS

All prospectively enrolled dogs received prednisolone, dexamethasone or both along with clopidogrel. Patients were randomized to receive Pentaglobin at 1 g/kg on up to 2 occasions, or to serve as controls. No additional immunosuppressive drugs were allowed within the first 7 days of treatment. Remission was defined as stable PCV for 24 hours followed by an increase in PCV.

RESULTS

Ten of 11 dogs from the treatment group and 2 of 3 dogs from the control group achieved remission and survived until hospital discharge. Survival and time to remission were not significantly different between groups. The volume of packed red blood cells transfused, normalized for body weight, was not significantly different between groups. Potential adverse reactions to Pentaglobin occurred in 2 dogs, but their clinical signs may have been related to the underlying disease.

CONCLUSIONS AND CLINICAL IMPORTANCE

Treatment with high-dose Pentaglobin was well tolerated by dogs with primary IMHA but no significant advantage was found in this small study. Additional studies examining larger groups and subpopulations of dogs with primary IMHA associated with a poorer prognosis are warranted.

Appraising the contemporary role of aspirin for primary and secondary prevention of atherosclerotic cardiovascular events

INTRODUCTION

Although the role of aspirin for primary prevention of atherosclerotic cardiovascular disease (ASCVD) has been disputed, its use in secondary ASCVD prevention is well established. Recent trials of primary prevention do not suggest a significant net benefit with aspirin, whereas accruing evidence supports adopting aspirin-free strategies in the context of potent P2Y₁₂ inhibition for the secondary prevention of selected patients undergoing percutaneous coronary intervention.

AREAS COVERED

This updated review aims at summarizing and appraising the pharmacological characteristics and the contemporary role of aspirin for the primary and secondary prevention of ASCVD.

EXPERT OPINION

Recent trials and metanalyses in the context of primary prevention highlighted a modest reduction in ischemic events with aspirin use, counterbalanced by a significant increase in bleeding events. However, ongoing studies on cancer prevention could modify the current paradigm of the unfavorable benefit-risk ratio of aspirin in patients with no overt ASCVD. Conversely, aspirin use is crucial for secondary ASCVD prevention, both in chronic and acute coronary syndromes. Nevertheless, after a brief period of dual antiplatelet therapy, patients at high bleeding risk may benefit from discontinuation of aspirin if a P2Y₁₂ inhibitor is used, hence reducing the bleeding risk with no rebound in thrombotic events.

Therapeutic Strategies for Treatment of Immune-Mediated Hemolytic Anemia

Immune-mediated hemolytic anemia is a common hematologic disorder in dogs. Disease management involves immunosuppression using glucocorticoids, potentially in combination with other medications such as azathioprine, cyclosporine, or mycophenolate mofetil. Therapeutic drug monitoring may enhance the utility and maximize the safety of cyclosporine and mycophenolate mofetil. The disease is proinflammatory and prothrombotic. Antithrombotic drug administration is therefore essential, and anticoagulant therapy should be initiated at the time of diagnosis. Additional therapies include red blood cell transfusion to support blood oxygen content. Future therapies may include therapeutic plasma exchange, anti-CD20 monoclonal antibodies, and complement inhibitors.

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs

Immune‐mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence‐based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases.

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.

Eicosanoids in platelets and the effect of their modulation by aspirin in the cardiovascular system (and beyond)

Platelets are important players in thrombosis and haemostasis with their function being modulated by mediators in the blood and the vascular wall. Among these, eicosanoids can both stimulate and inhibit platelet reactivity. Platelet Cyclooxygenase (COX)-1-generated Thromboxane (TX)A₂ is the primary prostanoid that stimulates platelet aggregation; its action is counter-balanced by prostacyclin, a product of vascular COX. Prostaglandin (PG)D₂ , PGE₂ and 12-hydroxyeicosatraenoic acid (HETE), or 15-HETE, are other prostanoid modulators of platelet activity, but some also play a role in carcinogenesis. Aspirin permanently inhibits platelet COX-1, underlying its anti-thrombotic and anti-cancer action. While the use of aspirin as an anti-cancer drug is increasingly encouraged, its continued use in addition to P₂ Y₁₂ receptor antagonists for the treatment of cardiovascular diseases is currently debated. Aspirin not only suppresses TXA₂ but also prevents the synthesis of both known and unknown antiplatelet eicosanoid pathways, potentially lessening the efficacy of dual antiplatelet therapies. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Mitophagy in Cardiomyocytes and in Platelets: A Major Mechanism of Cardioprotection Against Ischemia/Reperfusion Injury

Mitophagy, a process that selectively removes damaged organelles by autolysosomal degradation, is an early cellular response to ischemia. Mitophagy is activated in both cardiomyocytes and platelets during ischemia/reperfusion (I/R) and heart disease conditions. We focus on the molecular regulation of mitophagy and highlight the role of mitophagy in cardioprotection.

A Critical Appraisal of Aspirin in Secondary Prevention: Is Less More?

Aspirin represents the sine qua non for antiplatelet pharmacotherapy in patients with cardiovascular diseases because of its well-established role in secondary prevention and its widespread availability and affordability. Historical studies, conducted in an era that bears little resemblance to contemporary clinical practice, demonstrated large reductions in thrombotic risk when aspirin was compared with placebo, thus forming the evidence base promulgated in practice guidelines and recommendations. P2Y₁₂ inhibitors have mostly been studied in addition to aspirin; dual-antiplatelet therapy proved superiority compared with aspirin monotherapy for the prevention of ischemic events, despite increased bleeding risks. An alternative approach currently under investigation includes evaluation of single-antiplatelet therapy with P2Y₁₂ inhibitors alone versus dual-antiplatelet therapy after acute coronary syndromes or coronary stent implantation. As the availability of more effective antiplatelet agents increases, it is time to revisit the existing and long-standing paradigm supporting aspirin use for secondary prevention of atherothrombotic events. Ongoing trials will provide new evidence whether the less-is-more strategy is justified.

Effects of P2Y12 receptor antagonists beyond platelet inhibition--comparison of ticagrelor with thienopyridines

The effect and clinical benefit of P2Y12 receptor antagonists may not be limited to platelet inhibition and the prevention of arterial thrombus formation. Potential additional effects include reduction of the pro-inflammatory role of activated platelets and effects related to P2Y12 receptor inhibition on other cells apart from platelets. P2Y12 receptor antagonists, thienopyridines and ticagrelor, differ in their mode of action being prodrugs instead of direct acting and irreversibly instead of reversibly binding to P2Y12 . These key differences may provide different potential when it comes to additional effects. In addition to P2Y12 receptor blockade, ticagrelor is unique in having the only well-documented additional target of inhibition, the equilibrative nucleoside transporter 1. The current review will address the effects of P2Y12 receptor antagonists beyond platelets and the protection against arterial thrombosis. The discussion will include the potential for thienopyridines and ticagrelor to mediate anti-inflammatory effects, to conserve vascular function, to affect atherosclerosis, to provide cardioprotection and to induce dyspnea.

Chronic Treatment With Ticagrelor Limits Myocardial Infarct Size

Objective—

In a phase III clinical trial (PLATelet inhibition and patient Outcomes, PLATO), ticagrelor provided better clinical outcomes than clopidogrel in patients with acute coronary syndromes. In addition to P2Y 12 -receptor antagonism, ticagrelor prevents cell uptake of adenosine and has proven able to augment adenosine effects. Adenosine protects the heart against ischemia–reperfusion injury. We compared the effects of clopidogrel and ticagrelor on myocardial infarct size (IS).

Approach and Results—

Rats received oral ticagrelor (0, 75, 150, or 300 mg/kg/d) or clopidogrel (30 or 90 mg/kg/d) for 7 days and underwent 30-minute coronary artery ligation and 24-hour reperfusion. Area at risk was assessed by blue dye and IS by 2,3,5-triphenyl-tetrazolium-chloride. Cyclooxygenase-2 (COX2) enzyme activity was assessed by ELISA and expression by real-time polymerase chain reaction. Mechanism responsible was explored using adenosine-receptor antagonist (CGS15943, an A 2A /A 1 antagonist) or cyclooxygenase inhibition by either aspirin (5, 10, or 25 mg/kg) or specific cyclooxygenase-1 (SC560) or COX2 (SC5815) inhibitors. Ticagrelor, dose-dependently, reduced IS, whereas clopidogrel had no effect. Adenosine-receptor antagonism blocked the ticagrelor effect and COX2 inhibition by SC5815, or high-dose aspirin attenuated the IS-limiting effect of ticagrelor, whereas cyclooxygenase-1 inhibition or low-dose aspirin had no effect. Ticagrelor, but not clopidogrel, upregulated COX2 expression and activity. Also this effect was blocked by adenosine-receptor antagonism. Ticagrelor, but not clopidogrel, increased Akt and endothelial nitric oxide synthase phosphorylation.

Conclusions—

Ticagrelor, but not clopidogrel, reduces myocardial IS. The protective effect of ticagrelor was dependent on adenosine-receptor activation with downstream upregulation of endothelial nitric oxide synthase and COX2 activity.