Formulary
Aspirin (Acetylsalicylic Acid): Uses, Dosing, Side Effects and Indian Brand Names
Low-dose aspirin irreversibly inhibits platelet COX-1, forming the cornerstone of cardiovascular secondary prevention. Its role in primary prevention has been curtailed by recent trial evidence showing bleeding risk offsets benefit in low-risk patients.
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Clinically reviewed by Awaiting clinical review
Aspirin (Acetylsalicylic Acid): Uses, Dosing, Side Effects and Indian Brand Names
Low-dose aspirin irreversibly inhibits platelet COX-1, forming the cornerstone of cardiovascular secondary prevention. Its role in primary prevention has been curtailed by recent trial evidence showing bleeding risk offsets benefit in low-risk patients.
NEET PG High-Yield: Irreversible COX-1 inhibition (the only common irreversible COX inhibitor). Effect lasts the entire platelet lifespan (7-10 days). Reye syndrome -- do NOT give to children with viral fever. Samter triad (aspirin + nasal polyps + asthma). Ibuprofen antagonism of antiplatelet effect. Low-dose aspirin for pre-eclampsia prevention. ISIS-2 trial. Aspirin resistance concept. Chew the loading dose.
Clinical overview
Aspirin is among the oldest and most consequential drugs in medicine, with its antiplatelet property forming the backbone of cardiovascular secondary prevention worldwide. At low doses (75-150 mg), aspirin irreversibly inhibits platelet COX-1, preventing thromboxane A2 formation and platelet aggregation. This effect persists for the entire 7-10 day lifespan of the platelet because platelets lack a nucleus and cannot resynthesise COX. The Antithrombotic Trialists' Collaboration meta-analysis confirmed that low-dose aspirin reduces the risk of recurrent cardiovascular events by approximately 25% in secondary prevention. However, aspirin's role in primary prevention has been significantly revised: recent trials (ASPREE, ARRIVE, ASCEND) show that in low-to-moderate risk individuals, the bleeding risk (particularly GI and intracranial haemorrhage) offsets cardiovascular benefit. In Indian practice, low-dose aspirin (typically 75 mg or 150 mg enteric-coated) is standard in post-MI, post-stroke/TIA, stable angina, post-PCI (with clopidogrel as dual antiplatelet therapy), and peripheral arterial disease. Aspirin hypersensitivity can manifest as bronchospasm (aspirin-exacerbated respiratory disease/Samter triad with nasal polyps and asthma) or urticaria/angioedema. Reye syndrome -- acute hepatic encephalopathy -- contraindicates aspirin in children under 16 with viral febrile illness. Aspirin remains on the WHO Model List of Essential Medicines and India's NLEM.
Pharmacological class
Aspirin (Acetylsalicylic Acid) belongs to the Antiplatelet Agents / Non-Steroidal Anti-Inflammatory Drugs (Cyclo-oxygenase Inhibitor) class. Irreversibly acetylates and inhibits cyclo-oxygenase-1 (COX-1) in platelets, blocking thromboxane A2 (TXA2) synthesis. Since platelets are anucleate and cannot synthesise new COX, the inhibition lasts the entire platelet lifespan (7-10 days). At low doses (75-150 mg), the antiplatelet effect predominates; at higher doses (>300 mg), anti-inflammatory and analgesic effects emerge through COX-2 inhibition.
Indian brand names and formulations
Available as: Ecosprin (USV), Disprin (Reckitt), Loprin (Micro Labs), Aspicot (Alkem).
Tablets: 75 mg (enteric-coated), 150 mg (enteric-coated), 325 mg. Dispersible: 350 mg. Chewable: 81 mg (US formulation, less common in India). Also available in FDC with clopidogrel (Ecosprin Gold, Clopitab-A).
Regulatory status
Aspirin (Acetylsalicylic Acid) is classified under Schedule H (for prescription formulations); lower-dose OTC dispersible tablets available without prescription in some states in India under the Drugs and Cosmetics Act, 1940. Low-dose enteric-coated formulations are prescription-only. Dispersible aspirin for pain relief may be available OTC in certain states under varying enforcement.
Indications
- Secondary prevention of myocardial infarction
- Secondary prevention of ischaemic stroke and TIA
- Acute coronary syndrome (loading dose 325 mg chewed)
- Post-percutaneous coronary intervention (dual antiplatelet therapy with clopidogrel or ticagrelor)
- Stable angina pectoris
- Peripheral arterial disease
- Kawasaki disease (high-dose initially, then antiplatelet dose)
Dosing
Antiplatelet: 75-150 mg once daily (most Indian cardiologists use 75 mg or 150 mg). ACS loading: 325 mg chewed (not swallowed whole -- buccal absorption is faster). Kawasaki disease: 80-100 mg/kg/day in 4 divided doses during acute phase, then 3-5 mg/kg/day for 6-8 weeks.
Contraindications
- Active peptic ulcer disease or GI bleeding
- Aspirin-exacerbated respiratory disease (Samter triad: aspirin sensitivity + nasal polyps + asthma)
- Haemophilia and other bleeding disorders
- Children under 16 years with viral febrile illness (Reye syndrome risk)
- Severe hepatic impairment
- Third trimester of pregnancy (premature closure of ductus arteriosus)
Adverse effects
- GI irritation, dyspepsia, and gastric erosions (dose-dependent; enteric coating reduces but does not eliminate risk)
- GI bleeding (risk increases with concomitant NSAIDs, anticoagulants, alcohol, or Helicobacter pylori infection)
- Bronchospasm in aspirin-sensitive individuals
- Tinnitus and hearing loss (salicylism, at higher doses)
- Increased bleeding time (relevant peri-operatively)
- Reye syndrome in children (rare but devastating)
Drug interactions
- Warfarin and other anticoagulants: significantly increased bleeding risk; use combination only when clearly indicated (e.g., mechanical heart valves)
- Ibuprofen: may antagonise the irreversible antiplatelet effect of aspirin if taken BEFORE aspirin (competitive COX-1 binding) -- take aspirin 30 min before ibuprofen
- Methotrexate: aspirin reduces renal clearance of methotrexate, risk of toxicity at high MTX doses
- SSRIs: additive bleeding risk (SSRIs impair platelet serotonin uptake)
- ACE inhibitors: high-dose aspirin may reduce antihypertensive effect (but low-dose antiplatelet aspirin does not significantly interact)
Pregnancy and lactation
Low-dose aspirin (75-150 mg) is recommended in high-risk pregnancies for prevention of pre-eclampsia (ASPRE trial), started at 12-16 weeks. Contraindicated in the third trimester at analgesic doses due to risk of premature closure of the ductus arteriosus and prolonged labour.
Exam-style clinical scenario
A patient presents with acute chest pain, ECG shows ST elevation. Before reaching the cath lab, what medication should be given immediately? Aspirin 325 mg -- chewed, not swallowed -- for rapid buccal absorption. This reduces mortality in STEMI as demonstrated in ISIS-2.
Cost in India
Rs 5-20 for a strip of 10-14 tablets (75 mg or 150 mg). Ecosprin 75 is approximately Rs 0.50 per tablet.
Clinical governance
Author: MedNext Editorial Team. Clinical reviewer: Awaiting clinical review. Jurisdiction: India (Drugs and Cosmetics Act, 1940). Sources: CIMS India, Indian Pharmacopoeia. Publication state: Awaiting clinical review. Correction: Report errors at support@mednext.academy.
Frequently Asked Questions
Why is aspirin chewed and not swallowed in ACS?
Chewing the tablet breaks it into smaller particles and allows buccal absorption, achieving effective antiplatelet levels in approximately 15 minutes. Swallowing an enteric-coated tablet delays absorption to 60-90 minutes because the coating resists gastric acid dissolution. In acute MI, every minute of delay matters.
Why does ibuprofen antagonise aspirin's antiplatelet effect?
Ibuprofen is a reversible COX-1 inhibitor. If taken before aspirin, it occupies the COX-1 active site and prevents aspirin from acetylating Ser-530. When ibuprofen dissociates, COX-1 regains activity. If aspirin is taken first, it irreversibly acetylates COX-1 before ibuprofen can compete. Hence the recommendation: take aspirin 30 minutes before ibuprofen.
Should aspirin be used for primary prevention?
Current evidence (ASPREE, ARRIVE, ASCEND trials) does not support routine aspirin for primary prevention in low-to-moderate risk individuals. The bleeding risk, particularly GI and intracranial haemorrhage, offsets the modest cardiovascular benefit. It may still be considered in high-risk individuals (10-year ASCVD risk >20%) after careful risk-benefit discussion.
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