Drug Information: Aspirin
Aspirin, also known as acetylsalicylic acid (ASA), is a medication used to reduce pain, fever, or inflammation. It is a salicylate drug, often used as an analgesic (pain reliever), antipyretic (fever reducer), and anti-inflammatory medication. Aspirin also has an antiplatelet effect and is used in the long-term, low-dose treatment to prevent heart attacks, strokes, and blood clot formation. It works by inhibiting the production of prostaglandins and thromboxanes, which are responsible for pain, inflammation, and platelet aggregation.
Category
Antiplatelet
Mechanism of Action
Aspirin’s primary mechanism of action is the irreversible inhibition of cyclooxygenase (COX) enzymes, specifically COX-1 and COX-2. These enzymes are responsible for the production of prostaglandins and thromboxanes from arachidonic acid. Prostaglandins are involved in inflammation, pain, and fever, while thromboxane A2 (TXA2) is a potent stimulator of platelet aggregation. Aspirin acetylates a serine residue within the active site of COX enzymes, preventing the binding of arachidonic acid. COX-1 inhibition reduces the production of TXA2 in platelets, thereby inhibiting platelet aggregation for the lifespan of the platelet (approximately 7-10 days). COX-2 inhibition reduces the production of prostaglandins involved in inflammation and pain. Aspirin’s irreversible COX-1 inhibition is what gives it its unique antiplatelet properties, differentiating it from other NSAIDs, which are generally reversible COX inhibitors. Due to platelets lacking a nucleus, they cannot synthesize new COX enzymes during their lifespan, so the effect of aspirin persists until new platelets are produced.
Clinical Uses
Aspirin has a wide range of clinical applications, primarily due to its antiplatelet, analgesic, antipyretic, and anti-inflammatory properties. In the context of acute coronary syndromes (ACS), aspirin is a cornerstone of treatment. It is used in patients experiencing unstable angina, non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI) to prevent further clot formation and reduce the risk of subsequent cardiovascular events. Beyond ACS, aspirin is also used for secondary prevention in patients with a history of myocardial infarction, stroke, or other atherosclerotic cardiovascular diseases. Low-dose aspirin is often prescribed long-term to reduce the risk of future cardiovascular events. Additionally, aspirin is used for pain relief, fever reduction, and management of inflammatory conditions such as arthritis and rheumatic fever. Its use in these areas, however, has largely been supplanted by other NSAIDs with fewer gastrointestinal side effects. More recently, aspirin has also been investigated for its potential role in cancer prevention, particularly colorectal cancer, though more research is needed to confirm these findings.
Dosage
Adults:
*Analgesic/Antipyretic: 325-650 mg every 4 hours as needed, not to exceed 4000 mg per day.
*Antiplatelet (Acute Coronary Syndrome): Initial loading dose of 162-325 mg, followed by a maintenance dose of 75-100 mg daily.
*Antiplatelet (Secondary Prevention): 75-100 mg daily.
Pediatrics: (Consult with a physician before administering Aspirin to children, Reye’s syndrome is a risk.)
*Antipyretic: NOT RECOMMENDED for fever reduction in children due to the risk of Reye’s syndrome.
*Anti-inflammatory (e.g., Kawasaki disease): High-dose aspirin (80-100 mg/kg/day) followed by low-dose aspirin (3-5 mg/kg/day). Dosage and duration are dependent on disease activity and specialist recommendations.
Route of Administration: Oral. Aspirin is available in various forms, including tablets (enteric-coated and non-enteric-coated), chewable tablets, and suppositories.
Indications
* Acute Coronary Syndromes (Unstable Angina, NSTEMI, STEMI)
* Secondary Prevention of Myocardial Infarction and Stroke
* Pain Relief (Mild to Moderate Pain)
* Fever Reduction
* Inflammatory Conditions (e.g., Rheumatoid Arthritis, Osteoarthritis, Kawasaki Disease)
* Prevention of Thromboembolic Events in High-Risk Patients
Contraindications
* Known allergy or hypersensitivity to aspirin or other salicylates.
* Active bleeding (e.g., gastrointestinal bleeding, intracranial hemorrhage).
* Bleeding disorders (e.g., hemophilia, thrombocytopenia).
* Severe renal or hepatic impairment.
* Children and adolescents with viral infections (risk of Reye’s syndrome).
* Pregnancy (especially in the third trimester).
* Concomitant use with other anticoagulants or NSAIDs may increase the risk of bleeding.
* Patients with asthma exacerbated by NSAIDs.
FAQ
Q: What is aspirin used for?
A: Aspirin is used to reduce pain, fever, and inflammation. It also has antiplatelet effects, making it useful in preventing blood clots and cardiovascular events.
Q: How does aspirin work?
A: Aspirin works by inhibiting the production of prostaglandins and thromboxanes by irreversibly blocking COX-1 and COX-2 enzymes, reducing inflammation, pain, and platelet aggregation.
Q: What is the typical dosage of aspirin for pain relief?
A: The typical dosage for pain relief is 325-650 mg every 4 hours as needed, not to exceed 4000 mg per day.
Q: What are the common side effects of aspirin?
A: Common side effects include gastrointestinal upset, heartburn, nausea, and an increased risk of bleeding. Long-term use can lead to more serious complications such as stomach ulcers or kidney problems.
Q: Can children take aspirin?
A: Aspirin should generally be avoided in children and adolescents, especially those with viral infections, due to the risk of Reye’s syndrome.
Q: What should I do if I miss a dose of aspirin?
A: If you are taking aspirin regularly, take the missed dose as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.
Q: Can I take aspirin with other medications?
A: Aspirin can interact with other medications, such as anticoagulants, NSAIDs, and certain blood pressure medications. Consult your healthcare provider or pharmacist before taking aspirin with other medications to avoid potential interactions.
Q: What are enteric-coated aspirin tablets?
A: Enteric-coated aspirin tablets are designed to dissolve in the small intestine rather than the stomach. This can help to reduce the risk of stomach upset and ulcers associated with aspirin use.
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