title: [Dose-response of aspirin on platelet function in very elderly patients].
abstract: To assess the consequences of switching aspirin dosage from 100 mg/d to 40 mg/d on cardiovascular benefit, bleeding risk and platelet aggregation in very elderly patients.
  
  
  
  Arachidonic acid induced platelet aggregation(AA-Ag) was measured in 537 patients aged 80 or older treated with aspirin (100 mg/d). In the study, 100 patients with low on-treatment platelet aggregation and at high risk of bleeding and low risk of cardiovascular events, were switched to aspirin (40 mg/d) and their platelet aggregation was measured again 7 days later.Their bleeding and upper gastrointestinal symptoms were also recorded in following 3 months.
  
  
  
  The study observed a heterogeneous distributed aspirin 100 mg/d AA-Ag (range: 0.42% to 28.78%)in the 537 very elderly patients.Aspirin 100 mg/d AA-Ag before the switch in aspirin 40 mg/d group was 5.00%±2.32% and the rate of the patients with low on-treatment platelet aggregation was 71.00%. The rates of melena or occult blood positive, other minimal bleeding,upper gastrointestinal symptoms and a history of gastrointestinal bleeding in 40 mg/d group were higher than those in 100 mg/d group. On a regimen of aspirin 40 mg/d, AA-Ag increased to 11.21%±4.95%(range: 2.12% to 28.84%) with 95.00%of the patients with AA-Ag<20% and the rate of the patients with low on-treatment platelet aggregation was 15.00%. Multiple variable analysis revealed that aspirin 40 mg/d AA-Ag was significantly influenced by aspirin 100 mg/d AA-Ag, BMI and platelet counts. The rate of gastrointestinal bleeding decreased from 12.00% to 5.00%,and upper gastrointestinal symptoms decreased from 59.00% to 21.00% after the switch in 40 mg/d group.
  
  
  
  Switching aspirin dosage from 100 mg/d to 40 mg/d reduces the bleeding events and improves upper gastrointestinal symptoms, thus inhibiting platelet aggregation effectively in very elderly patients.
authors.affiliation: Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
authors.forename: X R
authors.initials: XR
authors.lastname: Feng
authors.affiliation: Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
authors.forename: M L
authors.initials: ML
authors.lastname: Liu
authors.affiliation: Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
authors.forename: F
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Fan
authors.affiliation: Department of Geriatrics, Peking University First Hospital, Beijing 100034, China.
authors.forename: Q P
authors.initials: QP
authors.lastname: Tian
mesh_terms: D000369:Aged, 80 and over; D016718:Arachidonic Acid / Q000009:adverse effects / Q000097:blood; D001241:Aspirin / Q000008:administration & dosage* / Q000009:adverse effects* / Q000097:blood* / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000139:chemically induced / Q000517:prevention & control; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests
chemical_list: D010975:Platelet Aggregation Inhibitors; D016718:Arachidonic Acid; D001241:Aspirin