From the Guidelines
An inpatient may be on ASA (aspirin) bid (twice daily) for antiplatelet therapy, typically to prevent blood clots in high-risk patients, with a recommended dosage of 81 mg taken twice daily, as supported by the most recent guidelines 1. The most common indications for this regimen include:
- Recent heart attack or stroke
- Coronary artery disease
- Peripheral artery disease
- Certain types of heart valve disease
- Atrial fibrillation (in combination with other anticoagulants) The twice-daily dosing is sometimes preferred over once-daily dosing because it may provide more consistent platelet inhibition throughout the day, as aspirin works by irreversibly inhibiting cyclooxygenase-1 (COX-1) enzyme, which reduces the production of thromboxane A2, a substance that promotes platelet aggregation and blood clotting 1. It's essential to note that while this regimen can be beneficial for some patients, it may increase the risk of bleeding, and the decision to use ASA bid should be based on an individual patient's risk-benefit profile, with patients being monitored for any signs of bleeding or other adverse effects 1. Key considerations for ASA therapy include:
- Initial dose: 162-325 mg
- Maintenance dose: 75-162 mg per day
- Duration: indefinitely, unless contraindicated or not tolerated
- Combination with other antithrombotic agents: may be necessary for certain patients, such as those with atrial fibrillation or mechanical heart valves 1.
From the Research
Aspirin Dosage for Inpatients
- The dosage of aspirin for inpatients can vary depending on the specific medical condition being treated 2, 3, 4, 5, 6.
- Studies have shown that low-dose aspirin (75-81 mg daily) can be effective in preventing cardiovascular events, such as myocardial infarction and stroke, in patients with established atherosclerotic cardiovascular disease 2, 3, 5.
- However, some studies suggest that twice-daily aspirin may be more effective in achieving a greater antiplatelet effect, particularly in patients with increased platelet turnover 4.
- In the context of venous thromboembolism prophylaxis after total hip arthroplasty, low-dose aspirin (81 mg twice daily) has been shown to be as effective as standard-dose aspirin (325 mg twice daily) in preventing symptomatic venous thromboembolism 6.
Twice-Daily Aspirin Regimen
- A twice-daily aspirin regimen may be prescribed for inpatients who require a higher level of antiplatelet activity, such as those with acute coronary syndrome or those undergoing percutaneous coronary intervention 4.
- The twice-daily regimen may help to overcome the time-dependent renewal of the drug target, leading to a greater antiplatelet effect 4.
- However, the evidence for the use of twice-daily aspirin in specific clinical scenarios is limited, and more research is needed to determine the optimal dosing regimen for different patient populations 2, 3, 5.