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Recent reports have suggested that aspirin effect might be influenced by bodyweight, with decreased efficacy in heavier individuals. We investigated the influence of bodyweight on aspirin pharmacodynamics in two independent datasets of patients taking non-enteric coated aspirin 100 mg QD for coronary artery disease (CAD). In the first dataset, 368 patients had their platelet aggregation assessed using VerifyNow Aspirin and measured in Aspirin Reaction Units (ARU). In the second dataset, 70 patients had serum thromboxane B2 (TXB2) dosage assessed by an ELISA assay and measured in pg/mL. Platelet aggregation was independently associated with bodyweight, with 8.41 (95% CI 1.86-14.97; adjusted p-value = 0.012) increase in ARU for every 10 kg. Furthermore, the rate of non-response to aspirin (defined as ARU ≥ 550) was significantly associated with increased bodyweight (adjusted p-value = 0.007), with OR = 1.23 (95% CI 1.06-1.42) for every 10 kg. Similar results were found considering body mass index (in kg/m 2 ), with 15.5 (95% CI 5.0 to 25.9; adjusted p-value = 0.004) increase in ARU for every 10 kg and non-response OR = 1.43 (95% CI 1.13 to 1.81, adjusted p-value = 0.003) for every 5 kg/m 2 . Moreover, serum TXB2 was higher in patients weighting more than 70 kg (222.6 ± 62.9 versus 194.9 ± 61.9 pg/mL; adjusted p-value = 0.018). In two different datasets of patients with CAD on non-enteric coated aspirin 100 mg QD, increased bodyweight was independently associated with impaired response to aspirin.