An antiplatelet drug
is a member of a class of pharmaceuticals
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
that decrease platelet aggregation and inhibit thrombus
A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
formation. They are effective in the arterial circulation, where anticoagulants have little effect.
They are widely used in primary and secondary prevention of thrombotic cerebrovascular or cardiovascular disease.
Choice of antiplatelet drug
A recent review states: "....low-dose aspirin increases the risk of major bleeding 2-fold compared with placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
. However, the annual incidence of major bleeding due to low-dose aspirin is modest—only 1.3 patients per thousand higher than what is observed with placebo treatment. Treatment of approximately 800 patients with low-dose aspirin annually for cardiovascular prophylaxis will result in only 1 additional major bleeding episode."
The most important antiplatelet drugs are:
- Cyclooxygenase inhibitor
COX-2 selective inhibitor is a form of non-steroidal anti-inflammatory drug that directly targets COX-2, an enzyme responsible for inflammation and pain. Targeting selectivity for COX-2 reduces the risk of peptic ulceration, and is the main feature of celecoxib, rofecoxib and other members of this...
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
- Adenosine diphosphate (ADP) receptor inhibitor
Adenosine diphosphate receptor inhibitor is a type of drug that inhibits some or all types of adenosine diphosphate receptors ....
Clopidogrel is an oral, thienopyridine class antiplatelet agent used to inhibit blood clots in coronary artery disease, peripheral vascular disease, and cerebrovascular disease. It is marketed by Bristol-Myers Squibb and Sanofi-Aventis under the trade name Plavix. The drug works by irreversibly...
Prasugrel is a novel platelet inhibitor developed by Daiichi Sankyo Co. and produced by Ube and currently marketed in the United States in cooperation with Eli Lilly and Company for acute coronary syndromes planned for percutaneous coronary intervention...
Ticagrelor is a platelet aggregation inhibitor produced by AstraZeneca. The drug was approved for use in the European Union by the European Commission on December 3, 2010...
Ticlopidine is an antiplatelet drug in the thienopyridine family. Like clopidogrel, it is an adenosine diphosphate receptor inhibitor. It is used in patients in whom aspirin is not tolerated, or in whom dual antiplatelet therapy is desirable...
- Phosphodiesterase inhibitor
A phosphodiesterase inhibitor is a drug that blocks one or more of the five subtypes of the enzyme phosphodiesterase , therefore preventing the inactivation of the intracellular second messengers cyclic adenosine monophosphate and cyclic guanosine monophosphate by the respective PDE...
- Glycoprotein IIB/IIIA inhibitors (intravenous use only)
- Abciximab (ReoPro)
Eptifibatide , is an antiplatelet drug of the glycoprotein IIb/IIIa inhibitor class. Eptifibatide is a cyclic heptapeptide derived from a protein found in the venom of the southeastern pygmy rattlesnake...
Tirofiban is an antiplatelet drug. It belongs to a class of antiplatelet named glycoprotein IIb/IIIa inhibitors...
- Adenosine reuptake inhibitor
An adenosine reuptake inhibitor is a type of drug which acts as a reuptake inhibitor for the purine nucleoside and neurotransmitter adenosine by blocking the action of one or more of the equilibrative nucleoside transporters . This in turn leads to increased extracellular concentrations of...
Dipyridamole is a drug that inhibits thrombus formation when given chronically and causes vasodilation when given at high doses over a short time.-Mechanism and effects:...
- Thromboxane inhibitors
- Thromboxane synthase inhibitors
- Thromboxane receptor antagonists
Terutroban is an antiplatelet agent developed by Servier Laboratories. , it is being tested for the secondary prevention of acute thrombotic complications in the Phase III clinical trial PERFORM .-Method of...
Prevention and treatment of arterial thrombosis
Treatment of established arterial thrombosis includes the use of Antiplatelet drugs and thrombolytic therapy. Antiplatelet drugs alter the platelet activation at the site of vascular damage crucial to the development of arterial thrombosis.
- Aspirin irreversibly inhibits the enzyme COX, resulting in reduced platelet production of TXA2 (thromboxane - powerful vasoconstrictor that lowers cyclic AMP and initiates the platelet release reaction).
- Dipyridamole inhibits platelet phosphodiesterase, causing an increase in cyclic AMP with potentiation of the action of PGI2 – opposes actions of TXA2
- Clopidogrel affects the ADP-dependent activation of IIb/IIIa complex
- Glycoprotein IIb/IIIa receptor antagonists block a receptor on the platelet for fibrinogen and von Willebrand factor. 3 classes:
- Murine-human chimeric antibodies (e.g., abciximab)
- Synthetic peptides (e.g., eptifibatide)
- Synthetic non-peptides (e.g., tirofiban)
- Epoprostenol is a prostacyclin that is used to inhibit platelet aggregation during renal dialysis (with or without heparin) and is also used in primary pulmonary hypertension.
Thrombolytic therapy is used in myocardial infarction, cerebral infarction, and, on occasion, in massive pulmonary embolism. The main risk is bleeding. Treatment should not be given to patients having had recent bleeding, uncontrolled hypertension or a hemorrhagic stroke, or surgery or other invasive procedures within the previous 10 days.
- Streptokinase forms a complex with plasminogen, resulting in a conformational change that activates other plasminogen molecules to form plasmin.
- Plasminogen activators (PA), tissue-type plasminogen activators (alteplase, tenecteplase) are produced by recombinant technology.
Drug toxicity is increased when mulitple antiplatelet drugs are used.Gastro intestinal bleeding is also seen in majority of the cases