Aspirin: Difference between revisions

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{{MedTemplate

| generic = Aspirin

| generic = Aspirin (acetylsalicylic acid; ASA)

| brand = Bayer

| brand = Bayer, Ecotrin, Bufferin, St. Joseph (low-dose 81 mg), Excedrin (with acetaminophen and caffeine)

| classes = NSAID

| structure =

| ~~intro~~ = Aspirin (acetylsalicylic acid) ~~is a non~~-~~selective~~ cyclooxygenase ~~inhibitor~~, ~~used as an~~ analgesic~~, antipyretic~~, anti-inflammatory, and, ~~at low doses~~, ~~antiplatelet medicine~~.

| uses = <vote slug="primary-cv-prevention-use">Primary cardiovascular prevention in selected patients (low-dose 81 mg, USPSTF guidance evolving)</vote>, <vote slug="secondary-cv-prevention-use">Secondary prevention of myocardial infarction and ischemic stroke (low-dose 81 mg daily, established benefit)</vote>, <vote slug="acute-mi-use">Acute myocardial infarction (162-325 mg chewed at first medical contact)</vote>, <vote slug="tia-acute-use">Transient ischemic attack / acute ischemic stroke management</vote>, <vote slug="preeclampsia-prophylaxis-use">Preeclampsia prophylaxis in pregnancy (81 mg after 12 weeks in high-risk patients, USPSTF)</vote>, <vote slug="mild-moderate-pain-use">Mild-to-moderate pain (FDA)</vote>, <vote slug="fever-use">Fever in adults (FDA; '''avoid in pediatric viral illness''')</vote>, <vote slug="kawasaki-disease-use">Kawasaki disease (FDA, pediatric)</vote>

| starting_dose = Antiplatelet: 81 mg PO once daily. Acute MI/stroke: 162-325 mg chewed. Analgesic: 325-650 mg PO every 4-6 hours as needed

| preparations = Tablets 81 (low-dose), 325, 500, 650 mg; chewable 81 mg; enteric-coated tablets; effervescent tablets; suppositories

| fda_max = 4000 mg/day (analgesic)

| pill_id =

| routes = Oral, rectal

| onset = Antiplatelet effect within 30-60 minutes; analgesic effect 30-60 minutes

| duration = '''Antiplatelet effect lasts the platelet's lifetime (~7-10 days)''' due to irreversible COX-1 acetylation; analgesic 4-6 hours

| halflife = Aspirin 15-30 minutes; salicylate metabolite 2-3 hours (concentration-dependent, saturable at high doses)<ref name="aspirin-label">FDA Prescribing Information, Bayer Aspirin (acetylsalicylic acid), Bayer HealthCare, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/020589s015lbl.pdf</ref>

| bioavailability = ~50% (oral; reduced by buffering and enteric coating but onset clinically similar)<ref name="aspirin-label" />

| pregnancy = Low-dose (81 mg) safe and indicated for preeclampsia prophylaxis after 12 weeks in high-risk patients per USPSTF; high-dose aspirin avoid third trimester due to premature ductus arteriosus closure and bleeding risk

| legal = [[USLegal:Over-the-counter|OTC]] in US at all standard strengths

| mechanism = <vote slug="aspirin-mech-claim">'''Irreversible''' covalent acetylation of cyclooxygenase enzymes (COX-1 and COX-2), distinguishing aspirin from all other NSAIDs, which inhibit reversibly. The platelet effect derives from COX-1 acetylation: platelets cannot synthesize new enzyme, so a single 81 mg daily dose abolishes thromboxane A2 production for the platelet's entire 7-10 day lifespan. Endothelial cells recover prostacyclin synthesis quickly because they have nuclei and can transcribe new COX. The analgesic, anti-inflammatory, and antipyretic effects come from the broader prostaglandin reduction.</vote> '''Reye syndrome''': rare hepatic encephalopathy in children given aspirin during viral illness, the basis of the firm pediatric viral-illness contraindication. Aspirin-exacerbated respiratory disease (Samter triad: asthma, nasal polyps, aspirin sensitivity) is a recognized cross-reactive hypersensitivity to all COX-1 inhibitors<ref name="aspirin-label" />.

}}

== References ==

[[Category:NSAIDs]]

[[Category:Antiplatelets]]

[[Category:Analgesics]]

[[Category:Antipyretics]]

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