title: Platelet inhibition by aspirin 81 and 325 mg/day in men versus women without clinically apparent cardiovascular disease.
abstract: Compared with men, women have greater platelet aggregation before and after low-dose aspirin. It is not known whether high-dose aspirin therapy brings residual platelet aggregation in women closer to that in men. Our objective was to compare inhibition of platelet aggregation in women and men after low- and high-dose aspirin. We enrolled healthy subjects (n=106) in a trial of 14 days of aspirin 81 mg/day followed by 14 days of 325 mg/day. Platelet function was measured at baseline and after the 2 aspirin doses. Women had greater baseline platelet activation measurements. After the 2 aspirin doses, men and women had near complete suppression of platelet aggregation to arachidonic acid in whole blood and in platelet-rich plasma (PRP), the direct cyclo-oxygenase-1 pathway affected by aspirin. For indirect pathways, women had significantly greater residual platelet activation to collagen and adenosine diphosphate (ADP) in whole blood after the 2 aspirin doses and in response to collagen and ADP in PRP after aspirin 325 mg/day only. After aspirin 325 mg/day, women continued to have greater residual platelet aggregation compared with men after aspirin 81 mg/day in response to collagen (p=0.016 in whole blood, p=0.037 in PRP), ADP (p<0.001 in whole blood, p=0.012 in PRP), and epinephrine (p=0.03 in PRP). Excretion of urinary thromboxane metabolite (urinary 11-dehydrothromboxane B2) decreased after aspirin to a similar extent in men and women. In conclusion, women continue to have greater residual platelet activity after high-dose aspirin compared with men treated with a lower dose of aspirin.
authors.affiliation: Division of General Internal Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. rqayyum@jhmi.edu
authors.forename: Rehan
authors.initials: R
authors.lastname: Qayyum
authors.forename: Diane M
authors.initials: DM
authors.lastname: Becker
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Yanek
authors.forename: Taryn F
authors.initials: TF
authors.lastname: Moy
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Becker
authors.forename: Nauder
authors.initials: N
authors.lastname: Faraday
authors.forename: Dhananjay
authors.initials: D
authors.lastname: Vaidya
mesh_terms: D000328:Adult; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D002318:Cardiovascular Diseases / Q000097:blood / Q000188:drug therapy; D005260:Female; D006400:Hematocrit; D006801:Humans; D008055:Lipids / Q000097:blood; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D010976:Platelet Count; D010979:Platelet Function Tests; D012737:Sex Factors; D018709:Statistics, Nonparametric
chemical_list: D008055:Lipids; D010975:Platelet Aggregation Inhibitors; D001241:Aspirin