aspirin effects
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A recent study, published in The Lancet, investigates whether aspirin effects at a given dose are modified based on a patient’s weight.

Acetylsalicylic acid, more commonly known as aspirin, is a non-steroidal anti-inflammatory drug that is used to treat pain, fever, and inflammation. Aspirin also suppresses the formation of blood clots and is recommended by doctors to reduce the risk of cardiovascular events, including heart attack or stroke. Despite its widespread use, however, aspirin is associated with only modest long-term reductions in cardiovascular events.

Current standard doses of aspirin may not be ideal for all patients

One proposed explanation for its modest effects is that almost all randomized trials investigating the effects of aspirin involve using one or two aspirin doses. As such, there are only a couple standard doses of aspirin that are used in clinics. These doses, however, may not be ideal for all patients; rather, there may be slightly modifying effects of weight and body size on the effectiveness of aspirin in its ability to prevent cardiovascular disease.

To investigate the effectiveness of aspirin based on patient weight, Rothwell and colleagues conducted a comprehensive analysis of previously published paper found on the Antithrombotic Trialists (ATT) collaboration and the Cochrane Collaboration Database of Systematic Reviews.

Higher doses of aspirin needed for higher weights

Their findings, published in The Lancet, show that low-dose aspirin (75-100mg) was less effective in reducing cardiovascular events in participants with increasing weight. Specifically, low-dose aspirin was most effective in participants with a weight between 50-69kg but not in those weighing more than 70kg. In contrast, the effectiveness of high-dose aspirin in reducing cardiovascular events increased with weight. Collectively these findings seem to suggest that low- and high-dose aspirin is more effective in patients with low and high body weights, respectively.

The authors further investigated the effect of the different doses of aspirin on improving outcomes in patients with colorectal cancer. Consistent with their findings regarding cardiovascular events, they found that the lower aspirin dose was more effective in patients less than 70kg, while the higher aspirin dose was more effective in patients 70kg or above.

Weight-based dosing has not been used for antiplatelet drugs like aspirin

Although weight-based dosing is a common strategy for other thrombolytics and intravenous antiplatelet treatments, it has never been utilized for oral antiplatelet drugs like aspirin. The current finding, however, suggests that using a weight-based dosing strategy for aspirin might lead to better outcomes in participants. In conclusion, the study suggests that perhaps doctors need to consider the patient’s body weight and size in order to determine the optimal and most effective dose of aspirin.

Written by Haisam Shah, BSc

Reference: Rothwell, P. M., Cook, N. R., Gaziano, J. M., Price, J. F., Belch, J. F., Roncaglioni, M. C., … & Mehta, Z. (2018). Effects of aspirin on risks of vascular events and cancer according to bodyweight and dose: analysis of individual patient data from randomised trials. The Lancet392(10145), 387-399.

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