Aspirin dose for preeclampsia prophylaxis: an argument for 162-mg dosing

The optimal aspirin dose for preeclampsia prevention remains controversial, with international guidelines lacking consensus on the most effective regimen. Aspirin is a proven intervention for reducing the risk of preeclampsia, particularly when initiated early in pregnancy. Its benefits stem from the selective inhibition of cyclooxygenase-1 (COX-1), reducing thromboxane A2 synthesis while preserving prostacyclin production, thereby restoring the vascular balance essential for placental health. A dose-response relationship has been established, with doses ≥100 mg showing significantly greater efficacy than lower doses. Furthermore, aspirin's pharmacological effects remain highly specific to COX-1 at the 162 mg dose, minimizing concerns about broader prostaglandin inhibition. Emerging evidence suggests that certain patient factors, such as altered pharmacokinetics during pregnancy or obesity, may reduce aspirin's effectiveness at lower doses (e.g., 81 mg). In these studies, aspirin resistance was successfully overcome with a 162 mg dose. While concerns regarding safety at this dose have been raised, contemporary randomized controlled trials utilizing a 150 mg dose have shown no increase in adverse effects compared to placebo. As such, current evidence increasingly supports 162 mg as the optimal dose for preeclampsia prevention, offering greater effectiveness than the commonly used 81 mg dose, without significant evidence of increased risk.