Sex differences in the platelet response to aspirin

Abstract

The metabolism of aspirin and its effect on platelets and fibrinolysis were evaluated in patients undergoing total hip replacement in an attempt to understand why its antithrombotic effect is chiefly manifested in men. A prospective study was done in 15 men and 17 women who received either 1.2 gm or 3.6 gm of aspirin daily. None of aspirin's effects correlated with the occurrence of thromboembolic disease (4 in men, 5 in women) in this small number of patients. However, platelet counts were higher in women, and platelet aggregation induced by collagen, ADP (adenosine diphosphate) and epinephrine was significantly greater in women before and after aspirin. There was no sex difference in malondialdehyde production or serum acetyl salicylic acid esterase activity. Salicylate levels were higher in women before and after operation, and fibrinolysis was increased in women postoperatively. This study suggests that a fundamental sex difference in platelet aggregation persists after aspirin ingestion. It is possible that this difference is related to aspirin's lack of effectiveness in preventing thromboembolism in women.