Aspirin
Acetylsalicylic acid (ASA)
Brand names:Bayer, Ecotrin, Bufferin, St. Joseph
A salicylate that irreversibly inhibits platelet cyclooxygenase, used in EMS primarily for suspected acute coronary syndrome and in select TCCC contexts for thromboprophylaxis during prolonged casualty evacuation. Aspirin at antiplatelet dose (81 to 324 mg) does not produce meaningful analgesia.
Pharmacology and Actions
Aspirin irreversibly acetylates cyclooxygenase-1 (COX-1) in platelets, blocking thromboxane A2 production for the lifespan of the platelet (approximately 7 to 10 days). The result is reduced platelet aggregation. At higher doses, aspirin also inhibits COX-2, producing anti-inflammatory and analgesic effects, but the antiplatelet effect dominates clinical use in EMS. The drug is rapidly absorbed orally and hydrolyzed to salicylate, which provides additional anti-inflammatory activity.
Indications
- Suspected acute coronary syndrome (chest pain consistent with cardiac ischemia)
- STEMI/NSTEMI in prehospital setting per ACLS and EMS protocols
- Thromboprophylaxis in prolonged casualty care when ordered by medical control
- Mild to moderate pain (higher analgesic doses, less common prehospital use)
- Fever reduction in adults (higher doses)
Absolute Contraindications
- Known aspirin or salicylate allergy
- Active gastrointestinal bleeding
- Hemorrhagic stroke or suspected intracranial bleeding
- Pediatric patients with viral illness (Reye syndrome risk)
- Severe hepatic impairment
- Recent major surgery with bleeding risk
Precautions and Side Effects
Gastrointestinal irritation, gastritis, and GI bleeding are the most common adverse effects with chronic use. Bronchospasm can occur in aspirin-sensitive asthmatics. Tinnitus signals salicylate toxicity at higher doses. The irreversible platelet effect means even a single dose impairs hemostasis for 7 to 10 days; this is therapeutic in ACS but a concern in trauma. Avoid in active hemorrhage. Caution in patients on anticoagulants (warfarin, DOACs) due to compounded bleeding risk.
Adult Dosing
Pediatric Dosing
Aspirin is generally avoided in pediatric patients (under 19 years) with viral illness due to Reye syndrome risk. Specific pediatric indications (Kawasaki disease, antiplatelet therapy in congenital heart disease) are managed under specialty care, not prehospital.
Pharmacokinetics
Peak Effect: PO: 1 to 2 hours after administration
Duration: Antiplatelet effect: 7 to 10 days (lifespan of platelet). Analgesic effect: 4 to 6 hours.
Storage and Handling
Store at controlled room temperature (15 to 30 degrees Celsius). Protect from moisture. Tablets become acidic and lose potency when exposed to humidity. Enteric-coated tablets should not be crushed; standard tablets can be chewed for ACS protocol.
Reconstitution:
Tablet form requires no reconstitution. Enteric-coated tablets are not used for ACS protocol; use standard chewable or non-coated tablets.
TCCC and TECC Role
Aspirin is not a core analgesic in the TCCC algorithm; it is used in select prolonged casualty care contexts for thromboprophylaxis when prolonged immobilization or evacuation increases venous thromboembolism risk. The 2026 guidelines do not list aspirin in the Combat Wound Medication Pack. On the civilian/TECC side, aspirin remains a standard prehospital intervention for suspected ACS and is carried by BLS providers under standing orders in most US EMS systems including Pennsylvania.
Aspirin is the cardiac drug providers reach for first when chest pain looks ischemic, and it works fast when chewed. The chewing is not optional; chewed tablets reach therapeutic levels significantly faster than swallowed tablets. In the tactical environment, aspirin earns its place mainly for preventing thromboembolism during long evacuations, not for analgesia. A single 324 mg dose impairs platelet function for over a week, which is therapeutic in ACS but problematic if the casualty later needs surgery or develops bleeding.
Giving aspirin to a chest pain patient without first ruling out aortic dissection or hemorrhagic stroke. The presentation can be similar to ACS, and aspirin worsens outcomes in both. When in doubt, focus on the highest-likelihood diagnosis given the full clinical picture, and consult medical command if dissection or stroke are reasonable considerations.
This drug profile is provided as educational reference material for trained medical providers. It is not medical advice, not a substitute for formal training, and not a substitute for current published guidelines or medical direction.
Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances are subject to additional handling, accountability, and documentation requirements per DEA and state law. Always verify dosing, indications, contraindications, and route of administration against current published guidelines and your local protocols before administration.
If this content is being viewed during a medical emergency, call 911 immediately and follow the direction of your local emergency dispatch and medical control. Do not use this reference as a substitute for emergency medical services.
Drug information evolves. Last reviewed dates and source citations are provided for each entry. Confirm currency against the cited source before clinical use.
Penn Tactical Solutions publishes this reference for educational purposes. PTS does not provide medical direction and does not assume responsibility for clinical decisions made in the field. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Educational reference for trained medical providers. Not medical advice. Not a substitute for formal training, current published guidelines, or medical direction. Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances require additional storage, accountability, and documentation per DEA and state law.
In a medical emergency, call 911. This reference is not a substitute for emergency medical services.
Verify dosing, indications, and contraindications against current published guidelines and your local protocols before administration. Confirm content currency against the source citation. Penn Tactical Solutions does not provide medical direction. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Aspirin
| PO | Suspected ACS (EMS): 324 mg PO chewed (4 baby aspirin or 1 adult tablet). TCCC prolonged care thromboprophylaxis: 81 to 162 mg PO daily per medical control. Antiplatelet maintenance: 81 mg PO daily. (Antiplatelet effect: within 30 minutes of chewed tablet. Analgesic effect: 30 to 60 minutes.) |