Antiplatelet / NSAID (irreversible COX inhibitor)
Aspirin (acetylsalicylic acid)
Irreversibly acetylates cyclo-oxygenase-1 in platelets, abolishing thromboxane A2 production for the platelet lifespan (7-10 days) and so inhibiting aggregation.
Brands
Ecosprin · Disprin · Bayer Aspirin
Adult dosing
Maximum 100 mg/day for antiplatelet indications| Indication | Dose | Route | Frequency |
|---|---|---|---|
| ACS loading dose | 300 mg | Oral, chewed or dispersed | Single dose |
| Secondary prevention maintenance | 75-100 mg | Oral | Once daily |
| Acute ischaemic stroke | 300 mg | Oral or rectal | Once daily for 14 days, then 75 mg daily |
| Pre-eclampsia prevention | 75-150 mg | Oral | Once daily at night from 12 weeks |
Paediatric dosing
Always confirm the weight and the local paediatric formulary| Indication | Dose | Route | Frequency |
|---|---|---|---|
| Kawasaki disease, acute phase | 30-50 mg/kg/day | Oral | Divided every 6 hours |
| Kawasaki disease, antiplatelet phase | 3-5 mg/kg/day | Oral | Once daily |
| General analgesia under 16 years | ContraindicatedReye syndrome risk | — | — |
Renal adjustment
Move the slider to the patient's eGFRAntiplatelet dose unchanged
- eGFR ≥ 30Antiplatelet dose unchanged
- eGFR < 30Antiplatelet dose with caution; avoid analgesic doses
Hepatic adjustment
- Cirrhosis with coagulopathyAvoid — bleeding and variceal risk
Practical notes
The things that go wrong at the bedside- Add a proton pump inhibitor when there are gastrointestinal risk factors or dual antiplatelet therapy.
- Chewing the loading dose speeds platelet inhibition.
DrZep structured dosing table (demo dataset, formulary-aligned) · DrZep. Confirm every dose against your local formulary and the patient's weight, renal function and comorbidities.
Indications
- Acute coronary syndrome — loading dose
- Secondary prevention after myocardial infarction, stroke or TIA
- Acute ischaemic stroke (after excluding haemorrhage)
- Peripheral arterial disease
- Kawasaki disease (specialist use)
Dosing summary
- ACS loading
- 300 mg chewed or dispersed once
- Maintenance (secondary prevention)
- 75-100 mg once daily
- Acute ischaemic stroke
- 300 mg daily for 14 days, then 75 mg daily (or switch to clopidogrel)
- Analgesic / antipyretic (adults)
- 300-900 mg every 4-6 h, maximum 4 g/day — rarely used now
Organ adjustment
Renal
- eGFR ≥ 30
- No change for antiplatelet doses
- eGFR < 30
- Avoid analgesic doses; antiplatelet dose usually continued with caution
- Dialysis
- Antiplatelet dose acceptable; bleeding risk increased
Hepatic
- Mild-moderate
- Use with caution
- Severe / cirrhosis with coagulopathy
- Avoid — bleeding and variceal risk
Monitoring
- 1Bleeding symptoms and haemoglobin
- 2Blood pressure and renal function when combined with ACE inhibitors or diuretics
- 3Consider a proton pump inhibitor if GI risk factors are present
Contraindications & cautions
Do not use / use with care
- Age under 16 years (Reye syndrome) except specialist indications
- Active peptic ulceration or major bleeding
- Aspirin-exacerbated respiratory disease / NSAID hypersensitivity
- Haemophilia and other severe bleeding disorders
- Third trimester of pregnancy at analgesic doses
Pregnancy & lactation
- Pregnancy
- Low-dose (75-150 mg) is used for pre-eclampsia prevention from 12 weeks. Avoid analgesic doses, especially in the third trimester (premature ductus closure, bleeding).
- Lactation
- Low dose is generally considered compatible; avoid high analgesic doses due to theoretical Reye risk.
Interactions
- Warfarin / DOACsMarkedly increased bleeding riskmajor
- Other NSAIDs (e.g. ibuprofen)GI bleeding risk and reduced cardioprotective effectmajor
- MethotrexateReduced renal clearance and methotrexate toxicitymajor
- SSRIsAdditive GI bleeding riskmoderate
- ACE inhibitors / diureticsReduced antihypertensive effect and renal impairment at high dosesmoderate
- ValproateDisplacement from protein binding, raised free valproatemoderate
Adverse effects
Common
- Dyspepsia
- Nausea
- Bruising and minor bleeding
- Epistaxis
Serious
- Upper GI haemorrhage
- Intracranial haemorrhage
- Bronchospasm in NSAID-sensitive asthma
- Salicylate toxicity in overdose
- Reye syndrome in children
Toxicity & overdose
Recognise and treat
- Salicylate poisoning: tinnitus, hyperventilation, mixed respiratory alkalosis with metabolic acidosis, hyperthermia, confusion
- Management: activated charcoal if early, IV fluids, urinary alkalinisation with sodium bicarbonate, correct potassium; haemodialysis for severe toxicity or level > 700 mg/L
Alternatives
- Clopidogrel (aspirin intolerance)
- Ticagrelor or prasugrel in ACS combinations
- Paracetamol for analgesia
Linked diseases & guidelines
ESC Guidelines for the management of acute coronary syndromes
Single unified ACS guideline covering STEMI and NSTE-ACS: reperfusion timing, antithrombotic strategy and secondary prevention.
European Society of CardiologyEurope2023
AHA/ASA Guidelines for the Early Management of Acute Ischemic Stroke
Time-critical thrombolysis and thrombectomy windows, imaging selection and early secondary prevention.
American Heart Association / American Stroke AssociationUSA2019
Demo monograph for educational use. Always confirm dose, route and interactions against your national formulary and the product label before prescribing.
Demo content. Educational decision support only. Verify every dose, citation and recommendation against your national formulary and the primary source before clinical use.