The Effect of Different Doses and Different Routes of Acetylsalicylic Acid Administration on Platelet Aggregation in Healthy Volunteers and Ischemic Stroke Patients

The purpose was to assess the effect of different doses and different routes of acetylsalicylic acid (ASA) administration on platelet aggregation and the comparison between platelet aggregation after the single and the repetitive administration of ASA in healthy individuals and in patients after ischemic stroke. The study group consists of 22 healthy individuals and 30 patients with documented ischemic stroke. Platelet aggregation was measured in healthy individuals: (a) twice before ASA and (b) 2 h after different single doses and different routes of ASA administration—(b₁) 500 mg orally, (b₂) 500 mg intravenously, and (b₃) 100 mg orally. We measured aggregability in healthy individuals after five consecutive days of 100 mg of ASA q.d. and in patients on chronic ASA 100 mg q.d. The VerifyNow was used with results expressed in aspirin reaction units (ARU). In healthy individuals, the dose—(b₁) 500 mg orally—reduced the aggregability to mean (SD) 392 (36) ARU (p < 0.001), (b₂) 500 mg intravenously to 428 (46) (p < 0.001) and (b₃) 100 mg orally to 460 (76) (p < 0.001). The suppression of aggregation after 500 mg was (p = 0.029) higher after the oral compared to intravenous administration, and the same is true for the suppression after single dose of 500 mg orally and 100 mg orally (p = 0.011). Oral dose 100 mg for 5 days in healthy individuals reduced aggregation to 405 (37) and in post-stroke patients to 433 (54). All doses of ASA, both orally and intravenously, have produced a significant reduction of platelet aggregation. Preference of the parenteral to oral application has not been established.