New insights into the mechanisms of action of aspirin and its use in the prevention and treatment of arterial and venous thromboembolism

Ymer H Mekaj,1,2 Fetije T Daci,2 Agon Y Mekaj3 1Institute of Pathophysiology, Faculty of Medicine, University of Prishtina, 2Department of Hemostasis and Thrombosis, National Blood Transfusion Center of Kosovo, 3Clinic of Neurosurgery, Faculty of Medicine, University of Prishtina, Prishtina, Kosovo Abstract: The antithrombotic action of aspirin has long been recognized. Aspirin inhibits platelet function through irreversible inhibition of cyclooxygenase (COX) activity. Until recently, aspirin has been mainly used for primary and secondary prevention of arterial antithrombotic events. The aim of this study was to review the literature with regard to the various mechanisms of the newly discovered effects of aspirin in the prevention of the initiation and development of venous thrombosis. For this purpose, we used relevant data from the latest numerous scientific studies, including review articles, original research articles, double-blinded randomized controlled trials, a prospective combined analysis, a meta-analysis of randomized trials, evidence-based clinical practice guidelines, and multicenter studies. Aspirin is used in the prevention of venous thromboembolism (VTE), especially the prevention of recurrent VTE in patients with unprovoked VTE who were treated with vitamin K antagonists (VKAs) or with non-vitamin K antagonist oral anticoagulants (NOACs). Numerous studies have shown that aspirin reduces the rate of recurrent VTE in patients, following cessation of VKAs or NOACs. Furthermore, low doses of aspirin are suitable for long-term therapy in patients recovering from orthopedic or other surgeries. Aspirin is indicated for the primary and secondary prevention as well as the treatment of cardiovascular diseases, including acute coronary syndrome, myocardial infarction, peripheral artery disease, acute ischemic stroke, and transient ischemic attack (especially in atrial fibrillation or mechanical heart valves). Aspirin can prevent or treat recurrent unprovoked VTEs as well as VTEs occurring after various surgeries or in patients with malignant disease. Recent trials have suggested that the long-term use of low-dose aspirin is effective not only in the prevention and treatment of arterial thrombosis but also in the prevention and treatment of VTE. Compared with VKAs and NOACs, aspirin has a reduced risk of bleeding. Keywords: arterial thrombosis, cyclooxygenase inhibitor, recurrent VTE, platele

New oral anticoagulants: their advantages and disadvantages compared with vitamin K antagonists in the prevention and treatment of patients with thromboembolic events

Ymer H Mekaj,1,2 Agon Y Mekaj,3 Shkelzen B Duci,4 Ermira I Miftari5 1Institute of Pathophysiology, Faculty of Medicine, University of Prishtina, 2Department of Hemostasis and Thrombosis, National Blood Transfusion Center of Kosovo, 3Clinic of Neurosurgery, Faculty of Medicine, University of Prishtina, 4Clinic of Plastic and Reconstructive Surgery, Faculty of Medicine, University of Prishtina, 5The Hospital and University Clinical Service of Kosovo, Prishtina, Kosovo Abstract: Despite the discovery and application of many parenteral (unfractionated and low-molecular-weight heparins) and oral anticoagulant vitamin K antagonist (VKA) drugs, the prevention and treatment of venous and arterial thrombotic phenomena remain major medical challenges. Furthermore, VKAs are the only oral anticoagulants used during the past 60 years. The main objective of this study is to present recent data on non-vitamin K antagonist oral anticoagulants (NOACs) and to analyze their advantages and disadvantages compared with those of VKAs based on a large number of recent studies. NOACs are novel direct-acting medications that are selective for one specific coagulation factor, either thrombin (IIa) or activated factor X (Xa). Several NOACs, such as dabigatran (a direct inhibitor of FIIa) and rivaroxaban, apixaban and edoxaban (direct inhibitors of factor Xa), have been used for at least 5 years but possibly 10 years. Unlike traditional VKAs, which prevent the coagulation process by suppressing the synthesis of vitamin K-dependent factors, NOACs directly inhibit key proteases (factors IIa and Xa). The important indications of these drugs are the prevention and treatment of deep vein thrombosis and pulmonary embolisms, and the prevention of atherothrombotic events in the heart and brain of patients with acute coronary syndrome and atrial fibrillation. They are not fixed, and dose-various strengths are available. Most studies have reported that more advantages than disadvantages for NOACs when compared with VKAs, with the most important advantages of NOACs including safety issues (ie, a lower incidence of major bleeding), convenience of use, minor drug and food interactions, a wide therapeutic window, and no need for laboratory monitoring. Nonetheless, there are some conditions for which VKAs remain the drug of choice. Based on the available data, we can conclude that NOACs have greater advantages and fewer disadvantages compared with VKAs. New studies are required to further assess the efficacy of NOACs. Keywords: novel oral anticoagulants, direct IIa and Xa inhibitors, vitamin K antagonist, venous thromboembolis

Development and validation of an oral anticoagulation knowledge tool (AKT)

© 2016 Obamiro et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background Assessing and improving patients' anticoagulation knowledge can lead to better treatment outcomes.While validated knowledge instruments exist for use in people taking warfarin, these tools are not necessarily applicable to patients taking direct-acting oral anticoagulants. Objective To develop and validate an oral anticoagulation knowledge instrument that is applicable to all oral anticoagulant medications. Methods Ten anticoagulation experts participated in the development of the Anticoagulation Knowledge Tool to ensure content validity. The knowledge instrument was administered to three groups of participants comprising of 44 pharmacists, 50 patients and 50 members of the general public. A subgroup of participants in the patient and pharmacist group were retested approximately 2-3 months after the initial testing. Statistical tests were conducted to determine the validity and reliability of the scale, and item analysis was used to determine the performance of individual questions. Results The 28-item instrument developed had a scale content validity index of 0.92, supporting content validity. The pharmacist group's mean score was significantly higher than that of the patient group, and the patient group scored significantly higher than the general public group (94% vs 62% vs 20%, respectively; p<0.001), supporting construct validity. Internal consistency reliability was acceptable with a Cronbach's a value of > 0.7 across the three groups, and the test-retest reliability was confirmed with a Pearson's correlation coefficient of 0.72 and 0.78 for the pharmacist and patient groups, respectively. Conclusion The Anticoagulation Knowledge Tool is a valid and reliable instrument that can be used in routine clinical practice to assess patients' anticoagulation knowledge