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Antiplatelet / NSAID / Antipyretic / Analgesic

Aspirin

Brand names: Disprin, Nu-Seals, Micropirin

Used in: Stroke & TIA

Low-dose aspirin is an antiplatelet for secondary prevention of cardiovascular events and in acute coronary syndromes; higher doses are analgesic and antipyretic.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Secondary prevention of myocardial infarction: 75-160 mg once daily. Prevention of cardiovascular morbidity in stable angina pectoris: 75-160 mg once daily. History of unstable angina pectoris, except during the acute phase: 75-160 mg once daily. Prevention of graft occlusion after coronary artery bypass grafting (CABG): 75-160 mg once daily. Coronary angioplasty, except during the acute phase: 75-160 mg once daily. Secondary prevention of transient ischaemic attack (TIA) and ischaemic cerebrovascular accident (CVA), provided intracerebral haemorrhage has been ruled out: 75-300 mg once daily. Acute myocardial infarction: loading dose 150-300 mg, then 75-160 mg daily thereafter.
Route: Oral. SPC 4.2: 'For oral use. The tablets should be swallowed with sufficient fluid (1/2 glass of water).'
Frequency: Once daily. SPC 4.2: 'Duration of administration: Long-term treatment with the lowest possible dose.' In acute myocardial infarction, a single 150-300 mg loading dose is followed by the lower daily dose.
Max: Maximum 300 mg a day FOR THE ANTIPLATELET INDICATIONS PUBLISHED HERE. SPC 4.2 verbatim: 'Aspirin should not be used at higher doses unless advised by a doctor, and the dose should not exceed 300 mg a day.' This is the ceiling of the Aspirin 75 mg tablets (antiplatelet) SPC and is NOT an analgesic or antipyretic ceiling - no analgesic posology or maximum exists anywhere in this bundle.
PRIOR VERIFY CARRY-FORWARD: the previous draft of this file was HELD for rendering that 300 mg/day cap as an unqualified, drug-level maximum on a page whose category still reads 'Antiplatelet / NSAID / Antipyretic / Analgesic' - roughly 13x below the analgesic maximum the page itself advertises. The maxDose above is now explicitly scoped to the antiplatelet indications; the underlying fix the verify asked for still stands - either scope this page to antiplatelet use, or source an SPC for a product licensed as an analgesic before republishing analgesic dosing. || INDICATION MATCH: this is a cardiology page whose existing dose leads with the antiplatelet indications (ACS and secondary prevention), and the fetched UK SPC for Aspirin 75 mg tablets doses precisely those indications by the oral route. || SCOPE STATED: the SPC covers antiplatelet use ONLY. Section 4.4 opens 'Aspirin is not suitable for use as an anti-inflammatory, analgesic or antipyretic.' Nothing in this bundle supports the analgesic/antipyretic regimen (300-900 mg every 4-6 hours, max 4 g/day) that the current page also carries, and nothing supports the page's Kawasaki-disease exception - source those separately before republishing them. || DIFFERENCES FROM THE CURRENT PAGE, all in the SPC's favour here: the page says antiplatelet '75 mg once daily' (SPC: 75-160 mg once daily), 'loading dose ACS: 300 mg' (SPC: 'The recommended loading dose is 150-300 mg followed by a lower dose (75-160 mg) daily thereafter'), and 'Acute ischaemic stroke/TIA: 300 mg for 2 weeks then 75 mg' (SPC gives 75-300 mg once daily for secondary prevention of TIA/CVA and states no 2-week step-down; the 2-week rule is a NICE recommendation, not SPC text, and is not in this bundle). || ELDERLY, verbatim: 'In general, acetylsalicylic acids should be used with caution in elderly patients who are more prone to adverse events. The usual adult dose is recommended in the absence of severe renal or hepatic insufficiency. Treatment should be reviewed at regular intervals.' 4.4 adds: 'Elderly patients are particularly susceptible to the adverse effects of NSAIDs and acetylsalicylic acid especially gastrointestinal bleeding and perforation which may be fatal.' || SURGERY, verbatim (4.4): 'There is an increased risk of haemorrhage and prolongation of bleeding time particularly during or after surgery (even in cases of minor procedures, e.g. tooth extraction). Use with caution before surgery, including tooth extraction. Temporary discontinuation of treatment may be necessary.' Bleeding effects 'may persist for a period of 4-8 days after acetylsalicylic acid discontinuation' (4.8). || CO-PRESCRIBING, verbatim (4.4): 'Concomitant treatment with Aspirin and drugs that alter haemostasis (i.e. anticoagulants, thrombolytic agents, antiplatelet agents, anti-inflammatory drugs and selective serotonin reuptake inhibitors) is not recommended, unless strictly indicated, because they may enhance the risk of haemorrhage. If the combination cannot be avoided, close observation for signs of bleeding is recommended.' || PAEDIATRIC (why paedDose is null), SPC 4.2 verbatim: 'Acetylsalicylic acid should not be administered to children and adolescents younger than 16 years, except on medical advice where the benefit outweighs the risk (see section 4.4).' 4.4: 'Recommended for use in adults and adolescents from 16 years of age. This medicinal product is not recommended for use in adolescents/children under 16 years unless the expected benefits outweigh the risks. Acetylsalicylic acid may be a contributory factor in the causation of Reye's Syndrome in some children.' No paediatric dose exists in this source and none has been invented; verify any under-16 use (including Kawasaki disease) against a children's formulary.

Dose adjustments

Renal

No numeric adjustment is given; severe impairment is a contraindication. SPC 4.3 lists 'Severe renal impairment' as a contraindication. 4.4: 'Acetylsalicylic acid should be used with caution in patients with moderately impaired renal or hepatic function (contraindicated if severe), or in patients who are dehydrated since the use of NSAIDs may result in deterioration of renal function.' 4.2 (elderly): 'The usual adult dose is recommended in the absence of severe renal or hepatic insufficiency.'

Hepatic

No numeric adjustment is given; severe impairment is a contraindication. SPC 4.3 lists 'Severe hepatic impairment' as a contraindication. 4.4: use with caution in moderately impaired hepatic function and 'Liver function tests should be performed regularly in patients presenting slight or moderate hepatic insufficiency.'

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Directions drink a full glass of water with each dose adults and children 12 years and over: take 4 to 8 tablets every 4 hours not to exceed 48 tablets in 24 hours unless directed by a doctor children under 12 years: consult a doctor

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-04-16. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

  • Previous hypersensitivity reactions (e.g. asthma, rhinitis, angioedema or urticaria) to salicylates/aspirin or other substances with a similar mechanism of action, especially NSAIDs; and a history of asthma caused by salicylates or NSAIDs (4.3)
  • Acute gastrointestinal ulcers (4.3)
  • A history of gastrointestinal bleeding or perforation (gastric or intestinal failure) caused by previous NSAID therapy (4.3)
  • Active or a history of recurrent gastric and duodenal ulcer/haemorrhage with episodes of proven ulceration or bleeding, or other kinds of bleeding such as cerebrovascular haemorrhages (4.3)
  • Haemorrhagic diathesis; coagulation disorders such as haemophilia and thrombocytopenia (4.3)
  • Severe hepatic impairment (4.3)
  • Severe renal impairment (4.3)
  • Severe cardiac insufficiency (4.3)
  • Doses greater than 100 mg/day during the third trimester of pregnancy (4.3, 4.6)
  • Methotrexate used at doses greater than 15 mg/week (4.3)

Side effects

  • Blood - common: increased bleeding tendencies. Uncommon: thrombocytopenia, agranulocytosis, aplastic anaemia. Not known: bleeding with prolonged bleeding time such as epistaxis and gingival bleeding ('Symptoms may persist for a period of 4-8 days after acetylsalicylic acid discontinuation'); overt (haematemesis, melaena) or occult gastrointestinal bleeding, which may lead to iron deficiency anaemia (more common at higher doses) (4.8)
  • Immune - uncommon: hypersensitivity reactions, angio-oedema, allergic oedema, anaphylactic reactions including shock (4.8)
  • Metabolism - not known: hyperuricaemia, hypoglycaemia (4.8)
  • Nervous system - uncommon: intracranial haemorrhage. Not known: headache, vertigo (4.8)
  • Ear - not known: reduced hearing ability, tinnitus (4.8)
  • Vascular - not known: haemorrhagic vasculitis (4.8)
  • Respiratory - uncommon: rhinitis, dyspnoea. Rare: bronchospasm, asthma attacks (4.8)
  • Gastrointestinal - common: dyspepsia, nausea, vomiting, diarrhoea. Rare: severe gastrointestinal haemorrhage, gastric or duodenal ulcers and perforation (4.8)
  • Hepatobiliary - rare: Reye's syndrome. Not known: hepatic insufficiency, increased hepatic enzymes (4.8)
  • Skin - uncommon: urticaria. Rare/not known: Stevens-Johnson syndrome, Lyell's syndrome, purpura, erythema nodosum, erythema multiforme - 4.4 requires that 'The treatment with Aspirin should be discontinued at the first appearance of skin rash, mucosal lesions, or any other sign of hypersensitivity' (4.4, 4.8)
  • Renal - not known: impaired renal function, acute renal failure (4.8)
  • Reproductive - not known: menorrhagia; 4.4 adds 'Aspirin is not recommended during menorrhagia where it may increase menstrual bleeding' (4.4, 4.8)

Monitoring

  • Bleeding - 4.4: 'Patients should report any unusual bleeding symptoms to their physician. If gastrointestinal bleeding or ulceration occurs the treatment should be withdrawn.'
  • Liver function tests regularly in patients with slight or moderate hepatic insufficiency (4.4)
  • Renal function - use with caution in moderate impairment and in dehydrated patients 'since the use of NSAIDs may result in deterioration of renal function' (4.4)
  • Regular review of elderly patients where prolonged therapy is required (4.4)
  • Skin and mucosa - discontinue at the first appearance of skin rash, mucosal lesions or any other sign of hypersensitivity (4.4)
  • Close observation for signs of bleeding whenever a combination with anticoagulants, thrombolytics, antiplatelets, anti-inflammatory drugs or SSRIs cannot be avoided (4.4)
  • Review the need for temporary discontinuation before surgery, including tooth extraction (4.4)

Clinical monograph

How it works

It irreversibly inhibits platelet cyclo-oxygenase-1, reducing thromboxane-A2-mediated aggregation for the lifespan of the platelet.

Prescribing in practice

  • Gastrointestinal irritation and bleeding occur — consider gastroprotection in at-risk patients.
  • It can trigger bronchospasm in aspirin-sensitive asthma.
  • Avoid in children under 16 (Reye's syndrome) except for specific indications; bleeding risk rises with other antithrombotics.

Monitoring

Watch for gastrointestinal symptoms and bleeding.

Counselling the patient

  • Take it with or after food.
  • Report indigestion, black stools or unusual bleeding.
  • Do not give aspirin to children unless specifically told to.

Evidence & guidelines

Established for secondary cardiovascular prevention; routine primary prevention is no longer generally recommended.

Reference: NICE NG185 (ACS, 2020); NICE NG128 (Stroke, 2022); NICE NG17 (Headaches); ESC Guidelines on ACS (2023); ASCEND trial (NEJM 2018); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.