Low-Dose Aspirin Dosing for Blood Clot Prevention After Surgery

Overseen By Ramakanth Yakkanti, MD

Age: 18+

Sex: Any

Trial Phase: Phase 2

Sponsor: University of Miami

Must be taking: Aspirin

Must not be taking: Anticoagulants, NSAIDs

Disqualifiers: VTE history, Malignancy, BMI > 40, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Prior Safety Data This treatment has passed at least one previous human trial

Approved in 4 Jurisdictions This treatment is already approved in other countries

Compensation: Varies

Number of Visits: Unknown

Duration: 4 weeks

5478 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial examines the effectiveness of low-dose aspirin in preventing blood clots after hip or knee replacement surgery. Researchers aim to determine if taking aspirin once daily is as effective as taking it twice daily. Participants will take 81 mg of aspirin either once or twice daily, starting the night before surgery and continuing for up to 28 days. This trial suits individuals planning hip or knee replacement surgery who have no history of blood clots, cancer, or conditions requiring blood thinners. As a Phase 2 trial, the research focuses on assessing the treatment's effectiveness in an initial, smaller group of participants.

Will I have to stop taking my current medications?

The trial does not specify if you need to stop taking your current medications, but if you are on blood thinners or have a condition that requires anticoagulation, you may not be eligible to participate.

Is there any evidence suggesting that this trial's treatments are likely to be safe?

Research shows that taking low-dose aspirin is generally safe for preventing blood clots after surgery. Studies have found that low-dose aspirin works well for people with different risk levels. One study discovered that the chance of getting blood clots after joint surgery was similar whether using aspirin or other blood-thinning medicines, indicating that aspirin is well-tolerated compared to other treatments.

Another study also supports that low-dose aspirin is a safe way to prevent clots. While aspirin might not be as strong as some other medicines in certain situations, it remains a safe choice for many people. Overall, aspirin has a good safety record, especially when used in low doses. ^{1 2 3 4 5}

Why are researchers excited about this trial's treatment for blood clots?

Researchers are excited about these aspirin dosing regimens for preventing blood clots after surgery because they explore how a low-dose aspirin strategy could optimize patient outcomes. Unlike more aggressive blood thinners, which can increase bleeding risk, low-dose aspirin might offer a safer balance between preventing clots and minimizing bleeding. The trial compares once-daily and twice-daily dosing, potentially providing insights into the most effective and convenient schedule for patients. By fine-tuning aspirin use, this approach could enhance recovery and safety in post-surgical care.

What evidence suggests that this trial's treatments could be effective for preventing blood clots after surgery?

Research shows that aspirin can help prevent blood clots, such as deep vein thrombosis (DVT), after joint surgery. Studies have found that aspirin is as effective as other blood thinners in stopping these clots. One study found that aspirin works just as well as rivaroxaban, a common blood thinner, in preventing clots after surgery. However, some research suggests that aspirin might not be as effective as other blood thinners in reducing DVT. Overall, aspirin remains a reliable option for preventing clots after surgery. This trial will compare two dosing regimens: one group will receive 81 mg aspirin once daily, while another group will receive 81 mg aspirin twice daily, to determine the most effective dosing schedule for clot prevention post-surgery. ^{1 2 6 7 8}

Who Is on the Research Team?

Victor H Hernandez, MD

Principal Investigator

University of Miami

Are You a Good Fit for This Trial?

This trial is for adults over 18 who are about to have hip or knee replacement surgery and can understand the consent form. It's not for those with a history of blood clots, cancer, mental illness, extreme obesity (BMI > 40), pregnancy, or conditions that make aspirin use unsafe.

Inclusion Criteria

I am scheduled for a first-time hip or knee replacement surgery.

Exclusion Criteria

I need blood thinners for a condition I already have.

Pregnancy

My BMI is over 40.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive 81 mg aspirin once or twice daily starting the night before surgery and continuing for up to 28 days post-surgery

4 weeks

Follow-up

Participants are monitored for safety and effectiveness after treatment, including incidence of thromboembolic events and adverse events

90 days

What Are the Treatments Tested in This Trial?

Interventions

• Aspirin

Trial Overview The study is testing if taking low-dose aspirin once a day is just as good at preventing blood clots after joint replacement surgery as taking it twice a day. Participants will receive either one or two doses daily.

How Is the Trial Designed?

Group I: Treatment Once Daily Experimental Treatment 1 Intervention

Participant receives 81 mg aspirin taken once daily beginning the night before surgery and up to 28 days post surgery.

Group II: Treatment Twice Daily Active Control 1 Intervention

Participant receives 81 mg aspirin taken twice daily (one in the morning and one at night) beginning at the night before surgery and up to 28 days post surgery.

Aspirin is already approved in European Union, United States, Canada, China for the following indications:

Approved in European Union as Aspirin for:

• Pain relief
• Fever reduction
• Inflammation
• Cardiovascular disease prevention
• Preeclampsia prevention

Approved in United States as Aspirin for:

• Pain relief
• Fever reduction
• Inflammation
• Cardiovascular disease prevention
• Preeclampsia prevention

Approved in Canada as Aspirin for:

• Pain relief
• Fever reduction
• Inflammation
• Cardiovascular disease prevention
• Preeclampsia prevention

Approved in China as Aspirin for:

• Pain relief
• Fever reduction
• Inflammation
• Cardiovascular disease prevention

Who Is Running the Clinical Trial?

University of Miami

Lead Sponsor

Trials

976

Recruited

423,000+

Published Research Related to This Trial

All six aspirin preparations tested effectively inhibited platelet aggregation to a similar extent, indicating their efficacy in reducing blood clotting, which is important for preventing heart attacks and strokes.

Ecotrin and S.R.A. showed delayed effects and inhibited platelet aggregation without measurable levels of aspirin in the bloodstream, suggesting a unique mechanism of action possibly involving acetylation of cyclooxygenase in the liver.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Aspirin kinetics and platelet aggregation in man. Siebert, DJ., Bochner, F., Imhoff, DM., et al.[2019]

In a study of 83 patients, daily aspirin (100 mg) significantly improved graft patency rates after aortocoronary bypass surgery, with 90% of grafts patent in the aspirin group compared to 68% in the placebo group at four months.

Aspirin also reduced the incidence of occlusions and postoperative ventricular arrhythmias, demonstrating its efficacy and safety in preventing complications after surgery without reported side effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Improved aortocoronary bypass patency by low-dose aspirin (100 mg daily). Effects on platelet aggregation and thromboxane formation. Lorenz, RL., Schacky, CV., Weber, M., et al.[2022]

A review of studies indicates that low dose aspirin (75-325 mg) does not show significant differences in safety across this range, with no increased bleeding events reported in randomized controlled trials.

Aspirin 325 mg daily may be at least as effective as 75 mg daily for preventing cardiovascular and cerebrovascular events, suggesting that higher doses could be considered based on individual patient assessments.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The dose of aspirin for the prevention of cardiovascular and cerebrovascular events. Fisher, M., Knappertz, V.[2019]

In a study of 36 high-risk patients undergoing major non-cardiac surgery, low-dose acetylsalicylic acid (aspirin) significantly reduced platelet function both before and after surgery compared to a placebo, indicating its effectiveness in inhibiting platelet aggregation.

The study found that while platelet function decreased in the placebo group postoperatively, it remained consistently low in the aspirin group, suggesting that aspirin maintains its antiplatelet effect throughout the perioperative period.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Platelet function assessed by whole-blood aggregometry in patients undergoing non-cardiac surgery. Oscarsson, A., Öster, S., Fredrikson, M., et al.[2013]

In a study of 100 patients undergoing carotid endarterectomy, a single pre-operative dose of 120 mg acetylsalicylic acid (ASA) did not significantly reduce the rate of emboli during or after the procedure.

There were no additional bleeding complications associated with ASA, indicating it is safe to use, but it did not provide the expected benefit in reducing emboli rates.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Emboli rate during and early after carotid endarterectomy after a single preoperative dose of 120 mg acetylsalicylic acid--a prospective double-blind placebo controlled randomised trial. Tytgat, SH., Laman, DM., Rijken, AM., et al.[2016]

In a study involving healthy volunteers who took varying doses of acetylsalicylic acid (ASA) for one week, all doses significantly inhibited platelet function and increased bleeding times, indicating its effectiveness in thrombosis prophylaxis.

The research found that a daily dose of around 100 mg of ASA maximized the effects on platelet function and bleeding time, suggesting that higher doses do not provide additional benefits.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effects of different doses of some acetylsalicylic acid formulations on platelet function and bleeding times in healthy subjects. McLeod, LJ., Roberts, MS., Cossum, PA., et al.[2019]

A study involving 46 healthy participants demonstrated that a novel 75 mg soft-gel capsule formulation of acetylsalicylic acid (ASA) is non-inferior to a marketed powder solution in reducing serum thromboxane B2 (TXB2), a marker for platelet aggregation.

Both formulations showed similar effectiveness in inhibiting TXB2, with no reported adverse events, suggesting that the soft-gel capsule could be a safe and effective alternative for preventing cardiovascular events.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Pharmacodynamics and pharmacokinetics of a novel, low-dose, soft-gel capsule of acetylsalicylic acid in comparison with an oral solution after single-dose administration to healthy volunteers: a phase I, two-way crossover study. Loprete, L., Leuratti, C., Scarsi, C., et al.[2021]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC10589573/

The efficacy and safety of aspirin in preventing venous ... Our updated meta-analysis showed that aspirin was inferior to when compared with other anticoagulants in VTE-related orthopedic major surgery.

2. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC11949201/

Aspirin Is as Effective and Safe as Oral Anticoagulants for ... Based on high-quality evidence from RCTs, aspirin is as effective and safe as OACs in preventing VTE, including DVT and PE, after joint arthroplasty, without ...

3. nature.com nature.com/articles/s41598-025-88493-4

Effectiveness of aspirin in preventing deep vein thrombosis ... The results showed that the continuation of aspirin did not reduce the incidence of DVT or proximal DVT, and no effect on DVT prophylaxis was ...

4. sciencedirect.com sciencedirect.com/science/article/abs/pii/S0049384814003533

Regular Article A systematic review on the effect of aspirin ... Our results do emphasize the need for developing specifically designed studies to test the safety and efficacy of ASA in the prevention of post-operative AT.

5. nejm.org nejm.org/doi/full/10.1056/NEJMoa1712746

Aspirin or Rivaroxaban for VTE Prophylaxis after Hip ... In the comparison with rivaroxaban, aspirin was found to be noninferior (P<0.001) but not superior (P=0.84) for the prevention of postoperative ...

6. jbjs.org jbjs.org/reader.php?rsuite_id=5ad49aa2-2c69-4f47-85c8-4d755beaa3be

Aspirin Is as Effective and Safe as Oral Anticoagulants for ... The relative risk (RR) of VTE following joint arthroplasty was 1.11 (95% confidence interval [CI], 0.93 to 1.32) for aspirin compared with OACs.

7. ashpublications.org ashpublications.org/hematology/article/2020/1/634/474338/Does-aspirin-prevent-venous-thromboembolism

Does aspirin prevent venous thromboembolism? The results of these trials suggest that aspirin has some efficacy in preventing VTE recurrence; patients who use aspirin as a long-term ...

8. pubmed.ncbi.nlm.nih.gov pubmed.ncbi.nlm.nih.gov/38753809/

Low-Dose Aspirin Is the Safest Prophylaxis for Prevention of ... Low-dose aspirin is a safe and effective method of prophylaxis in patients across various risk profiles.