From the Guidelines

Aspirin can be used for Deep Vein Thrombosis (DVT) prophylaxis, but it is not a recommended alternative to anticoagulation.

Aspirin is less effective at preventing recurrent VTE than anticoagulants, with an estimated reduction in risk of about one-third 1.
The use of aspirin for DVT prophylaxis is suggested in patients who are stopping anticoagulant therapy and do not have a contraindication to aspirin, but this is a weak recommendation with low-certainty evidence 1.
Aspirin may be considered in patients who decline extended anticoagulant therapy due to risk factors for bleeding or a lower than average risk of recurrence, but its net benefit is expected to be less than in clinical trials 1.

Aspirin has been shown to reduce the risk of recurrent VTE by 53 fewer events per 1,000 cases, but it also increases the risk of major bleeding by 3 more events per 1,000 cases 1.
The benefits of aspirin therapy must be balanced against its risk of bleeding and inconvenience, particularly in patients who have decided to stop anticoagulants 1.

From the FDA Drug Label

The FDA drug label for aspirin (acetylsalicylic acid) does not directly support its use for Deep Vein Thrombosis (DVT) prophylaxis.
The label mentions that aspirin contains an NSAID, which may cause severe stomach bleeding and has anticoagulant properties, but it does not provide information on its use for DVT prophylaxis 2.
Key warnings include the risk of stomach bleeding, allergic reactions, and Reye's syndrome, but do not address DVT prophylaxis.
The label advises against using aspirin in certain situations, such as in patients with a history of stomach problems or allergic reactions, but does not provide guidance on its use for DVT prevention. The FDA drug label does not answer the question.

Aspirin has been studied as a potential prophylactic agent for DVT in various clinical settings, including total hip replacement, total knee arthroplasty, and trauma patients 3, 4, 5, 6, 7.
A study published in 1986 found that aspirin was effective in preventing DVT in patients undergoing total hip replacement, with a significant reduction in phlebographic DVT compared to the control group 3.
A 2024 meta-analysis compared the efficacy of aspirin versus direct oral anticoagulants for VTE prophylaxis following primary total hip arthroplasty or total knee arthroplasty, and found that aspirin was as effective as rivaroxaban in preventing VTE, without an increased incidence of complications 4.
A 2016 retrospective case-control study found that preinjury aspirin use was associated with a reduced incidence of lower extremity DVT in trauma patients, particularly when used in combination with heparinoid prophylaxis 5.
A 2017 review article summarized the current evidence on the use of aspirin for VTE prophylaxis following arthroplasty, and concluded that aspirin is an effective, inexpensive, and safe form of VTE prophylaxis in patients without a major risk factor for VTE 6.
However, a 2023 meta-analysis found that aspirin was less effective than oral anticoagulants in thromboprophylaxis after major orthopedic surgery, although it was associated with a reduced risk of minor bleeding and total bleeding events 7.

Aspirin has been studied in various clinical settings, including total hip replacement, total knee arthroplasty, and trauma patients 3, 4, 5.
The efficacy and safety of aspirin for DVT prophylaxis may vary depending on the clinical setting and patient population, such as patients with a history of VTE or those undergoing major orthopedic surgery 4, 7.

The optimal dosage and administration of aspirin for DVT prophylaxis are not well established, although studies have used varying doses ranging from 81-650 mg per day 3, 4, 7.
Further research is needed to determine the optimal dosing regimen of aspirin and its long-term efficacy in preventing VTE 4.