Aspirin Dosage and Decision-Making: What Pharmacists Should Know

Few medications have been as commonly used for as many centuries as aspirin, nor as widely studied. Once widely recommended for broad preventative use, aspirin recommendations have narrowed based on indication, patient age, bleeding risk, and comorbid conditions. With this drug making headlines in the first hours of 2026, pharmacists are likely to receive questions about the optimal dosing, appropriate indications, and patient selection for aspirin use. Understanding its current recommendations can help pharmacists better serve their patients and offer suitable alternatives.

The History of Aspirin

Various forms of acetylsalicylic acid were derived from willow trees (Salix alba) and meadowsweet flowers in the 19th century, but the earliest use of willow for medicinal purposes dates back as far as 1500 BCE, when it is mentioned in the Ebers Papyrus, a medical text from ancient Egypt, as a pain reliever and anti-inflammatory agent.¹ Hippocrates also mentions willow bark and leaves as an analgesic and fever reducer, as do other writers from ancient Greece and Rome.^1,2

In 1763, the Royal Society published a paper by Edward Stone examining willow bark as a pain reliever. The paper served as the basis for experiments on the extraction and examination of the chemical structure of salicylic acid by Joseph Buchner (1828), Johann Pagenstecher, Carl Löwig (both 1830), and Charles Frédéric Gerhardt (1853). Felix Hoffmann, a chemist working for Bayer, synthesized aspirin in 1897, and his employer quickly patented and commercialized it. In 1950, the Guinness World Records listed aspirin as the world's most popular and most frequently sold painkiller.^1-4

Pharmaceutical developers around the world continue to explore different uses and indications for aspirin. In 2025 alone, sponsors initiated 100 clinical trials involving different administrations and dosages of aspirin for various indications.

Current Indications for Aspirin

Today, aspirin is classified as a nonsteroidal anti-inflammatory drug (NSAID). It works by inhibiting the activity of cyclooxygenase (COX) enzymes that produce prostaglandins and thromboxanes, which control pain, inflammation, blood flow, and clotting. By blocking COX enzymes, aspirin reduces pain, inflammation, fever, and blood clotting. However, it can also cause damage to the stomach lining and exacerbate both internal (bleeding or hemorrhage) and external bleeding.

OTC Use

Non-prescription aspirin is indicated for mild to moderate pain and fever reduction in various dosages (325 to 650 mg, Q4-6H, typically).

Though aspirin is available over the counter, it should not be taken daily without a physician's recommendation or supervision due to the increased risk of gastrointestinal and intracranial bleeding.

Primary Prevention for Atherosclerotic Cardiovascular Disease

For prescription or daily purposes, low-dose aspirin (75 to 100 mg; typically 81 mg, also known as "baby aspirin") can be taken as a primary preventative measure against atherosclerotic cardiovascular disease (ASCVD) for patients who meet a precise criteria, according to the US Preventive Services Task Force (USPSTF). Patients must be between 40 and 59 years of age with no signs or symptoms of cardiovascular disease and not at additional risk for bleeding, including medical conditions or taking other medications that increase bleeding risk.

The USPSTF has specifically recommended against initiating aspirin in patients 60 years of age or older as a primary prevention for ASCVD.⁸

Secondary Prevention for ASCVD

Aspirin is still recommended as a secondary preventative medication for patients who have already had a heart attack or stroke, have had a coronary artery stent installed, or have had coronary artery bypass graft surgery. In such cases, "there is strong evidence that aspirin helps prevent another such event," according to an article in the Journal of the American Medical Association.⁷

In a 2024 interview with Pharmacy Times, Snehal Bhatt, PharmD, AACC, BCPS, FASHP, professor of pharmacy practice at Massachusetts College of Pharmacy and Health Sciences, said aspirin's role as secondary prevention is evolving. "More recent data has [shown], and more recent guidelines have suggested, that P2Y12 inhibitor monotherapy may strike a better balance between still protecting patients from future cardiovascular events while having slightly lower bleeding rates compared to aspirin-based therapy," he said.⁸

What Pharmacists Need to Know

Pharmacists should always check the dosage of any patient taking aspirin regularly and should check other medications for bleeding risk. "Having patient-specific awareness of their disease and any other comorbidities that can enhance the risk of bleeding is really important for us as pharmacists because aspirin does have bleeding risk," Bhatt said.^6,8

REFERENCES

1. Connelly D. A history of aspirin. The Pharmaceutical Journal. Published September 26, 2014. https://pharmaceutical-journal.com/article/infographics/a-history-of-aspirin

2. Pearce J. The Controversial Story of Aspirin. worldneurologyonline.com. Published December 2, 2014. https://worldneurologyonline.com/article/controversial-story-aspirin/

3. Wood JN. From plant extract to molecular panacea: a commentary on Stone (1763) “An account of the success of the bark of the willow in the cure of the agues.” Philosophical Transactions of the Royal Society B: Biological Sciences. 2015;370(1666):20140317. doi:https://doi.org/10.1098/rstb.2014.0317

4. Montinari MR, Minelli S, De Caterina R. The First 3500 years of Aspirin History from Its Roots – a Concise Summary. Vascular Pharmacology. 2019;113(113):1-8. doi:https://doi.org/10.1016/j.vph.2018.10.008

5. Vane JR, Botting RM. The Mechanism of Action of Aspirin. Thrombosis Research. 2003;110(5-6):255-258. doi:https://doi.org/10.1016/s0049-3848(03)00379-7

6. USPSTF. Recommendation: Aspirin Use to Prevent Cardiovascular Disease: Preventive Medication | United States Preventive Services Taskforce. www.uspreventiveservicestaskforce.org. Published April 26, 2022. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/aspirin-to-prevent-cardiovascular-disease-preventive-medication

7. Peters AT, Mutharasan RK. Aspirin for Prevention of Cardiovascular Disease. JAMA. 2020;323(7):676. doi:https://doi.org/10.1001/jama.2019.18425

8. ASHP Midyear: Expert Discusses Evolving Role of Aspirin in Cardiovascular Disease Management. Pharmacytimes.com. Published December 9, 2024. Accessed January 2, 2026. https://www.pharmacytimes.com/view/expert-discusses-evolving-role-of-aspirin-in-cardiovascular-disease-management