Aspirin, chemically known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug (NSAID) and a member of the salicylate family. It reduces pain, fever, and inflammation, and inhibits the aggregation of platelets, the blood components involved in clot formation. These effects underlie its use both as a symptom-relieving medicine and in the treatment and prevention of certain cardiovascular events. Its principal limitations include gastrointestinal injury and increased bleeding risk. (medlineplus.gov)
Chemical identity
Aspirin has the molecular formula and a molar mass of approximately . In its pure form, it is a white crystalline substance. Its structure consists of a benzene ring bearing adjacent carboxylic acid and acetoxy groups; the systematic name 2-acetoxybenzoic acid describes this arrangement. (pubchem.ncbi.nlm.nih.gov)
Aspirin is an acetylated derivative of salicylic acid. Its ester group can undergo hydrolysis, producing salicylic acid and acetic acid. This reaction also contributes to its conversion into salicylate after administration. (pubchem.ncbi.nlm.nih.gov)
Mechanism of action
Aspirin acts on cyclooxygenase (COX), an enzyme involved in the formation of prostaglandins and thromboxanes from arachidonic acid. Prostaglandins participate in pain, fever, and inflammatory responses, but also have normal physiological functions, including protection of the stomach lining. Suppression of their formation therefore accounts for both therapeutic effects and some adverse effects. (nobelprize.org)
A distinctive feature of aspirin is its irreversible acetylation of cyclooxygenase. In platelets, inhibition of COX-1 reduces production of thromboxane A₂, a mediator that promotes platelet aggregation. The effect persists beyond the presence of aspirin in the circulation because the affected enzyme remains inactivated; recovery depends substantially on the appearance of newly formed platelets. This is the basis of aspirin’s antiplatelet action. (pubmed.ncbi.nlm.nih.gov)
Although aspirin is often described informally as a “blood thinner,” its principal antithrombotic action is inhibition of platelet function rather than direct inhibition of coagulation factors. (ncbi.nlm.nih.gov)
Medical uses
Pain, fever, and inflammatory symptoms
Aspirin is used to relieve mild to moderate pain and reduce fever and inflammatory symptoms. Oral preparations include conventional tablets, chewable tablets, and extended-release formulations. It is also an ingredient in combination medicines, whose effects and risks depend on the other active ingredients as well as aspirin itself. (medlineplus.gov)
Cardiovascular treatment and prevention
Aspirin has established uses in people experiencing or recovering from a heart attack and in preventing selected ischemic cardiovascular events. Its antiplatelet action can reduce the formation of artery-blocking clots. Prevention of recurrent events in people with established cardiovascular disease is termed secondary prevention, whereas prevention of a first event is termed primary prevention. These settings have different balances of benefit and bleeding risk. (medlineplus.gov)
For primary prevention, benefit is not universal. In its April 26, 2022 assessment, the United States Preventive Services Task Force found only a small net benefit among adults aged 40–59 with a calculated ten-year cardiovascular risk of at least 10% and no increased bleeding risk. It found no net benefit from initiating aspirin for primary prevention in adults aged 60 or older. These findings concern people without established cardiovascular disease, not all cardiovascular uses of aspirin. (uspreventiveservicestaskforce.org)
Aspirin’s role in preventing ischemic stroke is distinct from its effects on hemorrhagic stroke: inhibition of platelet function can prevent some clot-related events while increasing the risk of bleeding within the skull. (uspreventiveservicestaskforce.org)
Other clinical uses
Aspirin is also used in specific clinical settings, including Kawasaki disease, rheumatic fever, and selected pregnancy-related conditions. These uses are separate from ordinary treatment of pain or fever and involve condition-specific medical protocols. (medlineplus.gov)
Adverse effects and limitations
Important adverse effects include gastrointestinal irritation, peptic ulceration, and gastrointestinal bleeding. Aspirin can also increase intracranial bleeding risk. In preventive use, these harms must be distinguished from the reduction in ischemic events; a reduction in clot-related disease does not necessarily imply an overall net benefit. (uspreventiveservicestaskforce.org)
Aspirin can cause hypersensitivity reactions, including respiratory reactions in susceptible people with asthma. Its use in children and adolescents with viral illnesses is associated with Reye syndrome, a rare, serious disorder affecting the liver and brain. (medlineplus.gov)
Interactions with other medicines can alter safety or effectiveness. Other antiplatelet drugs and anticoagulants may increase bleeding risk, while ibuprofen can interfere with aspirin’s antiplatelet effect under some conditions of combined use. (medlineplus.gov)
Pregnancy-related risks depend on dose and clinical context. The US Food and Drug Administration’s warning about NSAID exposure around 20 weeks of pregnancy or later concerns fetal kidney dysfunction and reduced amniotic fluid. The warning explicitly distinguishes prescribed low-dose aspirin, at 81 mg, for particular pregnancy-related conditions from other NSAID use. (fda.gov)
Excessive exposure can cause salicylate poisoning. Manifestations may include tinnitus, vomiting, rapid breathing, confusion, and severe disturbances of acid–base balance. Toxicity can follow a large ingestion or repeated excessive exposure. (medlineplus.gov)
Historical development
Bayer registered the name Aspirin as a trademark and marketed acetylsalicylic acid in powder form in 1899. Tablets followed in 1900. The medicine’s early commercial use preceded a detailed understanding of its molecular mechanism by several decades. (bayer.com)
In 1971, John Vane and other researchers published work showing that aspirin-like drugs inhibited prostaglandin formation. This provided a mechanistic explanation for their analgesic, antipyretic, and anti-inflammatory effects. Vane shared the 1982 Nobel Prize in Physiology or Medicine with Sune Bergström and Bengt Samuelsson for discoveries concerning prostaglandins and related biologically active substances. (nobelprize.org)
References
- Aspirin: MedlinePlus Drug Informationmedlineplus.gov
- Aspirin overdose: MedlinePlus Medical Encyclopediamedlineplus.gov
- Recommendation: Aspirin Use to Prevent Cardiovascular Disease: Preventive Medicationuspreventiveservicestaskforce.org
- Aspirin and heart disease: MedlinePlus Medical Encyclopediamedlineplus.gov
- Aspirin | C9H8O4 | CID 2244 - PubChempubchem.ncbi.nlm.nih.gov
- The mechanism of action of aspirin.pubmed.ncbi.nlm.nih.gov
- The mechanism of the effect of aspirin on human platelets. I. Acetylation of a particulate fraction proteinpubmed.ncbi.nlm.nih.gov
- Health Technology Assessmentncbi.nlm.nih.gov
- FDA recommends avoiding use of NSAIDs in pregnancy at 20 weeks or later because they can result in low amniotic fluidfda.gov
- Aspirin™ – Surprisingly Versatilebayer.com
- John R. Vane - Nobel Lecturenobelprize.org
- Bengt Samuelsson - Nobel Lecturenobelprize.org