Aspirin

Emergency & Prehospital

• Suspected acute coronary syndrome (chest pain or ischemic symptoms): chewed aspirin early, unless it is contraindicated or the patient already took it. It is the first antiplatelet drug in every EMS level.
• Confirmed STEMI or NSTE-ACS: aspirin pairs with a P2Y12 inhibitor (dual antiplatelet therapy, DAPT). See clopidogrel
• Fibrinolysis: aspirin is part of the STEMI adjunct regimen. Timing around the lytic is in fibrinolytics.

ED / ICU / Transport

• Acute coronary syndrome after the first hour: antiplatelet therapy continues alongside anticoagulation (see heparin and enoxaparin)
• Secondary prevention after MI, PCI or stroke: long-term low-dose aspirin. Cardiology sets the maintenance dose.
• Transient ischemic attack or minor stroke: short-course DAPT with clopidogrel follows protocol (an off-label combination that guidelines recommend). Do not give aspirin for suspected acute stroke in the field. Start it only after imaging excludes hemorrhage, and follow thrombolysis timing

Other Uses

• Minor aches, pains and fever: the OTC label indication, not an EMS one
• Kawasaki disease (pediatric; specialist-directed regimen, not an OTC label use): see Pediatric Dosing

Doses vary by protocol; follow local protocols and medical direction.

Available Forms

• Chewable 81 mg tablet (low-dose): Most EMS and transport crews carry this form. Two tablets are 162 mg. Four tablets are 324 mg.
• Uncoated 325 mg tablet: One tablet is 325 mg. Chew it for acute ACS dosing, because swallowing it whole is slower. Stock varies by agency.
• 81 mg enteric-coated tablet: It is a delayed-release product. Don't substitute it for acute chewed dosing.
• Prescription combinations (for example, extended-release aspirin with dipyridamole) are for long-term prevention. They are not for acute use.

Adult Dosing

Pediatric Dosing

Preparation & Administration

• Route: oral only. Chew the tablet thoroughly and swallow with water if the patient is alert enough to do so safely.
• Form: use non-enteric-coated tablets for acute dosing. Enteric coating slows absorption.
• Verify the strength: count tablets against the mg target (for example, 2 × 81 mg = 162 mg; 4 × 81 mg = 324 mg).
• Swallowing: do not give to a patient who cannot protect the airway or swallow safely.
• Documentation: record the drug, the mg dose, the form, the time and any home dose.

Contraindications

• Known hypersensitivity to aspirin or any other pain reliever or NSAID (the label's "allergic to aspirin or any other pain reliever/fever reducer")
• Prior bronchospasm or reaction to aspirin or NSAIDs (including aspirin-exacerbated respiratory disease)
• Active gastrointestinal bleeding: this NSAID can cause severe stomach bleeding, and the label says so
• Children and teenagers with flu-like symptoms or chickenpox: Reye syndrome
• Recent tonsillectomy or oral surgery: avoid for 7 days unless a doctor directs otherwise (label)

Precautions

• Asthma: the OTC label says to ask a doctor before use if you have asthma. Ask about prior wheeze with NSAIDs.
• Anticoagulants, P2Y12 inhibitors and thrombolytics: the bleeding risk adds up. The ACS combination is intended, so monitor.
• Peptic ulcer or prior GI bleed: bleeding risk is higher. The acute dose does not change, but reassess.
• Older adults: GI bleeding risk climbs with age
• Suspected overdose or chronic high dosing: salicylate toxicity is possible. See the Overdose section.

Hold / Reassess If

• Melena, hematemesis or other overt bleeding: stop further aspirin and reassess
• New wheeze, stridor or dyspnea after a dose: stop and treat per protocol
• Hives, facial or throat swelling: stop and treat anaphylaxis per protocol
• Suspected acute stroke before imaging excludes hemorrhage: do not give in the field
• Known bleeding disorder, severe thrombocytopenia or recent intracranial hemorrhage: hold or reassess per protocol and medical direction

Common

• Stomach upset, heartburn and epigastric discomfort
• Easy bruising, nosebleeds and gum bleeding (antiplatelet effect)
• Nausea

Serious / Life-Threatening

Overdose & Toxicity Management

• Toxidrome: tinnitus, tachypnea, vomiting, confusion, metabolic acidosis; children may present with altered mental status
• Immediate management: airway, breathing and circulation; IV access; check glucose; supportive care per protocol
• Salicylate level: check the level; see salicylate
• Alkalinization: sodium bicarbonate per protocol (see sodium bicarbonate). Low potassium blocks urinary alkalinization, so correct the potassium
• Airway and ventilation: avoid intubation if you can. If you do intubate, match the high minute ventilation the patient had before. A fall in ventilation worsens acidemia
• Antidote: there is no specific antidote. Hemodialysis follows EXTRIP criteria (see salicylate). Bring toxicology in early

Clinically Significant Interactions

• Pediatrics: Reye syndrome is the main risk. Avoid aspirin in children and teenagers with viral illness. Kawasaki disease runs on a specialist regimen. Point to the Pediatric Dosing table and don't repeat doses here. The OTC label says to consult a doctor under 12.
• Neonates: No specific adjustment is established in the sources reviewed. It is not an EMS use.
• Pregnancy: the OTC label says to ask a health professional before use if pregnant. It also says not to use aspirin at 20 weeks or later unless a doctor definitely directs it, because of risk to the unborn child and complications during delivery. Suspected ACS in pregnancy needs clinician or medical-control direction. No specific adjustment for the acute dose is established in the sources reviewed.
• Lactation: if the patient is breast-feeding, the OTC label says to ask a health professional first. The sources reviewed establish no specific adjustment for the acute dose.
• Older Adults: GI bleeding risk is higher. The acute dose does not change. Check for anticoagulant and NSAID use.
• Renal Impairment: the sources reviewed establish no specific adjustment for the acute dose. In severe renal disease, reassess bleeding risk.
• Hepatic Impairment: the sources reviewed establish no specific adjustment.
• Obesity / Dosing Weight: adult doses are fixed. They are not weight-based.

• Scope: EMTs, AEMTs and paramedics commonly give aspirin under protocol. The protocol varies by state and agency.
• Storage & Stability: room temperature, dry, away from heat, per the package label.
• Carried Concentration: Solid oral only. Carry the 81 mg chewable and 325 mg tablets as the protocol specifies. Keep enteric-coated products apart so nobody grabs the wrong form.
• Infusions in Transport: not applicable.
• Altitude / Environment: the sources reviewed don't address altitude or environment specifically.
• Handoff Essentials: time and mg dose, chewed or swallowed, form, any home dose, bleeding signs and any wheeze.

Mechanism of Action

• Irreversible acetylation of platelet COX-1 → blocks thromboxane A2 formation → reduced platelet aggregation
• Platelets cannot make new COX-1 → the effect lasts the platelet lifespan, not the plasma half-life
• Higher doses also give analgesic and anti-inflammatory effects (OTC label use)

Pharmacokinetics

• Half-life: aspirin's plasma half-life is short, about 15–20 min at low doses per secondary sources (not primary-verified). Its active metabolite, salicylate, has a dose-dependent, saturable half-life of hours. That half-life lengthens at toxic doses. For the acute dose, the platelet effect is what matters clinically
• Metabolism: rapidly hydrolysed to salicylic acid
• Elimination: renal, as salicylate and metabolites

Generic Name

Aspirin (acetylsalicylic acid)

Brand Names

Bayer and store brands (OTC); many generic 81 mg chewable, 81 mg enteric-coated and 325 mg tablets

Pharmacologic Class

Nonsteroidal anti-inflammatory drug (salicylate); irreversible cyclooxygenase inhibitor

Therapeutic Class

Antiplatelet agent; analgesic; antipyretic

Controlled Substance

Not controlled

ISMP High-Alert

No

Look-Alike / Sound-Alike

None commonly reported; 81 mg chewable and enteric-coated tablets look alike