An antiplatelet drug (antiaggregant), also known as a platelet agglutination inhibitor or platelet aggregation inhibitor, is a member of a class of pharmaceuticals that decrease platelet aggregation and inhibit thrombus formation. They are effective in the arterial circulation, where anticoagulants have little effect.
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where they help keep the bite area unclotted long enough for the animal to obtain some blood. As a class of medications, anticoagulants are used in therapy for thrombotic disorders. Oral anticoagulants (OACs) are taken by many people in pill or tablet form, and various intravenous anticoagulant dosage forms are used in hospitals. Some anticoagulants are used in medical equipment, such as sample tubes, blood transfusion bags, heart-lung machines, and dialysis equipment. One of the first anticoagulants, warfarin, was initially approved as a rodenticide.
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.
A thrombus, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to prevent bleeding, but can be harmful in thrombosis, when clots obstruct blood flow through healthy blood vessels.
Thrombolysis, also called fibrinolytic therapy, is the breakdown (lysis) of blood clots formed in blood vessels, using medication. It is used in ST elevation myocardial infarction, stroke, and in cases of severe venous thromboembolism.
A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functioning properly. Signs and symptoms of a stroke may include an inability to move or feel on one side of the body, problems understanding or speaking, dizziness, or loss of vision to one side. Signs and symptoms often appear soon after the stroke has occurred. If symptoms last less than one or two hours, the stroke is a transient ischemic attack (TIA), also called a mini-stroke. A hemorrhagic stroke may also be associated with a severe headache. The symptoms of a stroke can be permanent. Long-term complications may include pneumonia and loss of bladder control.
Ticlopidine is an antiplatelet drug in the thienopyridine family which is an adenosine diphosphate (ADP) receptor inhibitor. Research initially showed that it was useful for preventing strokes and coronary stent occlusions. However, because of its rare but serious side effects of neutropenia and thrombotic thrombocytopenic purpura it was primarily used in patients in whom aspirin was not tolerated, or in whom dual antiplatelet therapy was desirable. With the advent of newer and safer antiplatelet drugs such as clopidogrel and ticagrelor, its use remained limited.
Alteplase (t-PA) is a thrombolytic medication, used to treat acute ischemic stroke, acute ST-elevation myocardial infarction, pulmonary embolism associated with low blood pressure, and blocked central venous catheter. It is given by injection into a vein or artery. Alteplase is the same as the normal human plasminogen activator and is synthesized via recombinant DNA technology from vascular endothelial cells. Alteplase causes the breakdown of a clot by inducing fibrinolysis.
A cerebral infarction is an area of necrotic tissue in the brain resulting from a blockage or narrowing in the arteries supplying blood and oxygen to the brain. The restricted oxygen due to the restricted blood supply causes an ischemic stroke that can result in an infarction if the blood flow is not restored within a relatively short period of time. The blockage can be due to a thrombus, an embolus or an atheromatous stenosis of one or more arteries. Which arteries are problematic will determine which areas of the brain are affected (infarcted). These varying infarcts will produce different symptoms and outcomes. About one third will prove fatal.
Rivaroxaban, sold under the brand name Xarelto among others, is an anticoagulant medication used to treat and prevent blood clots. Specifically it is used to treat deep vein thrombosis and pulmonary emboli and prevent blood clots in atrial fibrillation and following hip or knee surgery. It is taken by mouth.
A watershed stroke is defined as a brain ischemia that is localized to the vulnerable border zones between the tissues supplied by the anterior, posterior and middle cerebral arteries. The actual blood stream blockage/restriction site can be located far away from the infarcts. Watershed locations are those border-zone regions in the brain supplied by the major cerebral arteries where blood supply is decreased. Watershed strokes are a concern because they comprise approximately 10% of all ischemic stroke cases. The watershed zones themselves are particularly susceptible to infarction from global ischemia as the distal nature of the vasculature predisposes these areas to be most sensitive to profound hypoperfusion.
Ancrod is a defibrinogenating agent derived from the venom of the Malayan pit viper. Defibrinogenating blood produces an anticoagulant effect. Ancrod is not approved or marketed in any country. It is a thrombin-like serine protease.
Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. Specifically it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests. It is taken by mouth.
A coronary stent is a tube-shaped device placed in the coronary arteries that supply blood to the heart, to keep the arteries open in the treatment of coronary heart disease. It is used in a procedure called percutaneous coronary intervention (PCI). Coronary stents are now used in more than 90% of PCI procedures. Stents reduce angina and have been shown to improve survivability and decrease adverse events in an acute myocardial infarction.
Hormone replacement therapy (HRT), also known as menopausal hormone therapy (MHT) or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. These symptoms can include hot flashes, vaginal atrophy, accelerated skin aging, vaginal dryness, decreased muscle mass, sexual dysfunction, and bone loss. They are in large part related to the diminished levels of sex hormones that occur during menopause.
Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. The term "vitamin K antagonist" is technically a misnomer, as the drugs do not directly antagonise the action of vitamin K in the pharmacological sense, but rather the recycling of vitamin K.
Left atrial appendage occlusion (LAAO), also referred to as Left atrial appendage closure (LAAC) is a treatment strategy to reduce the risk of left atrial appendage blood clots from entering the bloodstream and causing a stroke in patients with non-valvular atrial fibrillation (AF).
Ponatinib is an oral drug developed by ARIAD Pharmaceuticals for the treatment of chronic myeloid leukemia (CML) and Philadelphia chromosome–positive (Ph+) acute lymphoblastic leukemia (ALL). It is a multi-targeted tyrosine-kinase inhibitor. Some forms of CML, those that have the T315I mutation, are resistant to current therapies such as imatinib. Ponatinib has been designed to be effective against these types of tumors.
Apixaban, sold under the brand name Eliquis among others, is an anticoagulant medication used to treat and prevent blood clots and to prevent stroke in people with nonvalvular atrial fibrillation. Specifically it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests. It is taken by mouth.
Darexaban (YM150) is a direct inhibitor of factor Xa created by Astellas Pharma. It is an experimental drug that acts as an anticoagulant and antithrombotic to prevent venous thromboembolism after a major orthopaedic surgery, stroke in patients with atrial fibrillation and possibly ischemic events in acute coronary syndrome. It is used in form of the maleate. The development of darexaban was discontinued in September 2011.
