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Paramedic primer: Aspirin

Mechanisms, roles and potential risk: What medics need to know about aspirin

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It’s late in the evening when you are your partner are dispatched for an elderly female who fell. On arrival, you find a conscious, alert and oriented elderly female who reports that she tripped over a rug and fell. She reports that she did not lose consciousness, but she did strike her head on a nearby table.

There is no obvious bleeding, however, you observe a small hematoma. Vitals are within normal limits, pupils are equal and reactive, and the patient answers all questions appropriately.

At this time, she does not wish to be transported to the hospital. As part of your patient refusal protocol, you review the patient’s prescribed medications. While reviewing her medications, you notice that she takes a daily 81 mg aspirin. You remember that many older adults take a daily aspirin, referred to as a blood thinner, which presents an increased risk of bleeding.

But what exactly is aspirin?

Common forms of aspirin

Acetylsalicylic acid (ASA), also known as aspirin, is a non-steroidal anti-inflammatory with cyclooxygenase inhibitor activity; and is a member of the benzoic acids, the salicylates and the phenyl acetates [5]. Common brand names include [1]:

  • Arthriten Inflammatory Pain
  • Ascomp
  • Aspi-cor
  • Aspir-low
  • Bayer Aspirin
  • Bayer Womens
  • Bc Arthritis
  • Bc Original Formula
  • St. Joseph’s Aspirin
  • Fasprin
  • Fiorinal
  • Goody’s Body Pain
  • Goody’s Extra Strength
  • Goody’s PM
  • Miniprin

However, aspirin is also found in over-the-counter medications, such as Alka-seltzer, Alka-seltzer Fruit Chews, Excedrin and Excedrin PM Triple Action [1]. As such, some individuals may be utilizing these medications on a regular basis and not realize that they are taking aspirin. The most common doses are 81 mg, referred to as “baby aspirin,” and 325 mg full-strength. Tablets come in coated or non-coated chewable varieties.

Remain consistent once you’ve established the patient’s weight, ensure you know what’s in your containers and practice dosing calculations to prevent medication administration errors

Aspirin roles and mechanism

Aspirin has many roles, including [5]:

  • Non-steroidal anti-inflammatory drug
  • Non-narcotic analgesic
  • Platelet aggregation inhibitor
  • Antipyretic
  • Cyclooxygenase 2 inhibitor (COX-2)
  • Cyclooxygenase 1 inhibitor (COX-1)
  • Prostaglandin antagonist
  • Teratogenic agent
  • Anticoagulant
  • Plant activator
  • EC (prostaglandin-F synthase) inhibitor
  • Drug allergen
  • Geroprotector

Due to both its anti-inflammatory and antipyretic effects, it is often used as a pain reliever and fever reducer [5]. Aspirin is also used for the prevention of blood clots and strokes because it inhibits platelet aggregation; it prevents platelets from clumping or sticking together to produce a clot [1,6]. Aggregation inhibition occurs through aspirin’s ability to interfere with thromboxane A2 in platelets, caused by COX-1 inhibition [1]. Thromboxane A2 is a primary lipid responsible for platelet aggregation [1]. This aggregation then leads to an increased risk of cardiac events or strokes. In contrast, anticoagulants such as heparin or warfarin (Coumadin), act directly on the body’s ability to produce clots by slowing down the process and inhibiting clotting factors [6].

Aspirin also blocks prostaglandin synthesis via targeting of the COX-1 and COX-2 pathways [1]. Prostaglandins increase sensitivity to pain and are potent irritators that have been shown to cause headaches [1]. Through the prevention of inflammatory prostaglandins, pain thus may be stopped at the pain receptors, and the symptoms of “pain” prevented [1].

Video: OPQRST explained

Aspirin contraindications/risks

As with any medication, aspirin is not without risks. One of the most significant risks is the increased risk of bleeding due to inhibited platelet aggregation. Even a minor laceration may result in significant bleeding for someone taking any form of blood thinning medication.

Additionally, aspirin can irritate the stomach lining, resulting in gastrointestinal upset, ulcers and GI bleeds [4]. There is also the risk of allergic reaction to aspirin [3].

Another significant risk, and the risk of greatest concern to most EMS professionals, is the increased risk of hemorrhagic (bleed) stroke [3]. Head injuries, however minor, especially in elderly patients, may result in a ruptured blood vessel and hemorrhagic stroke due to inhibited platelet aggregation. Additionally, some patients utilize aspirin in conjunction with other blood thinners or anticoagulant medications, such as warfarin, Xarelto, Eliquis, Pradaxa, Lovenox or Plavix, resulting in an even greater risk of bleeding.

Aspirin and children

Children under the age of 16 should not be given aspirin unless directed by a healthcare provider because of the risk of Reye syndrome [7]. Reye syndrome typically occurs in children who have taken aspirin, or aspirin-containing products for the treatment of symptoms of a viral illness, however, the exact cause is unknown [7]. The most common symptoms are a full or bulging fontanelle, sleepiness or lethargy, sudden and prolonged vomiting, combative behavior, rapid breathing and heart rate, seizures, coma, increased intracranial pressure, increased irritability and high-pitched cry [7]. As with any child, a full medical history should be obtained, including recent illness and any medications ingested. Children with symptoms of Reye syndrome should receive immediate medical attention to prevent death.

Aspirin overdose

Aspirin overdose may occur either acutely or chronically. In an acute overdose, an individual consumes a large quantity of aspirin at one time [2].

In a chronic overdose, a normal daily dose builds up in the body over time, causing symptoms which may occur due to dehydration or decreased kidney function [2]. Chronic overdoses are most commonly seen in older adults during hot weather [2]. Symptoms include [2]:

  • Tachypnea
  • Slow, labored breathing
  • Wheezing
  • Ringing in the ears
  • Blurred vision
  • Agitation
  • Confusion
  • Altered mental status
  • Syncope
  • Coma
  • Seizures
  • Drowsiness
  • Severe headache
  • Unsteadiness
  • Problems moving
  • Rash
  • Diarrhea
  • Heartburn
  • Nausea
  • Vomiting (sometimes bloody)
  • Stomach pain

Additional symptoms of chronic overdose include fatigue, slight fever, altered mental status, syncope, tachycardia and uncontrollable tachypnea [2].

Overdose treatment includes IV administration of sodium bicarb and dextrose, as well as potassium if hypokalemia is present [8]. Mechanical ventilation may be required [8]. Depending on provider protocols, EMS providers may be permitted to administer an initial dose of sodium bicarb via IV in the field. As with any overdose, attempt to get a complete medical history and determine how much of the substance was ingested. Additionally, poison control may be contacted for additional information and guidance.

Case resolution

So back to our elderly fall patient. Remember, she is alert, oriented and refusing transport. So what do you do? Knowing everything that you know about aspirin now, you advise her of the risk of an unseen head bleed or stroke, as well as the risk of death from unseen injury.

She is able to repeat back to you that she understands these risks, but she still does not wish to be transported. She reports that her daughter will be home soon and is currently staying with her to help her. You advise her that she or her daughter should contact 911 immediately if any changes in her condition occur, such as a headache, confusion, vision changes or difficulty staying awake. She assures you that she will, and will tell her daughter what happened as soon as she arrives home.

Per your protocol, medical command must be contacted any time a patient suffers a fall and is on a blood thinning medication. You do so, and advise the doctor of the situation, who feels that you have adequately explained the risks, and permits the refusal. You fill out a patient refusal form, which the patient signs, and a copy is left with her. Upon parting, you assure her again, that she can call at any time if she needs you. She thanks you, and you return to quarters. Another job well done!


  1. Aspirin. (2024, April 14). Drugbank Online.
  2. Aspirin Overdose. (n.d.). Mount Sinai.
  3. Mayo Clinic Staff. (2023, April 20). Daily aspirin therapy: Understand the benefits and risks. Mayo Clinic.
  4. Michos, E. D. (n.d.). Is taking aspirin good for your heart?. Johns Hopkins Medicine.,at%20higher%20risk%20of%20bleeding.
  5. National Center for Biotechnology Information (2024). PubChem Compound Summary for CID 2244, Aspirin. Retrieved April 15, 2024 from
  6. National Library of Medicine. (2022, January 31). Blood thinners. Medline Plus.,together%20to%20form%20a%20clot.
  7. Reye Syndrome. (n.d.). Boston Children’s Hospital.
  8. Runde TJ, Nappe TM. Salicylates Toxicity. (Updated 2023 Jul 10). In StatPearls [Internet]. StatPearls Publishing.
Megan A. Mason, MPH, NRP, FFII, is a firefighter/paramedic and EMS educator in rural Western Pennsylvania. She holds a Bachelor of Arts in Health Science from La Roche University and a Master of Public Health from Kent State University, where she focused on the intersection of public health and paramedicine. Currently, her focus is on improving the quality of education available to rural EMS providers, as well as community education focusing on CPR, first aid, and stop the bleed in rural areas.