Individual variation in platelet aggregability and serum thromboxane B2 concentrations after low-dose aspirin.
The effects of low daily oral doses of aspirin (40 mg/day) on platelet aggregability and serum thromboxane B2 concentrations were studied in 19 poststroke patients. Although platelet aggregation was reduced significantly after 1 week, there was wide individual variation in the inhibition of platelet function in spite of marked decreases of serum thromboxane B2 concentrations by greater than 90% (from 224 +/- 58 to 8 +/- 8 ng/ml). There was no correlation between collagen-induced platelet aggregability and serum thromboxane B2 concentration before aspirin administration in the range 100-350 ng/ml, but after 1 week of repeated administration of aspirin, there was a correlation between platelet aggregability and serum thromboxane B2 concentrations of less than 25 ng/ml (r = 0.68, p less than 0.01). However, platelet inhibition was insufficient even in some patients with markedly decreased thromboxane B2 concentrations (less than 5 ng/ml). Our results suggest that individual variation of platelet aggregability in response to low-dose aspirin may be due to variation not only in the degree of inhibition of thromboxane A2 production but also in the relative dependence of platelet aggregation on extra-arachidonic pathways.
Tohgi
H
H
Department of Neurology, Iwate Medical University, Morioka City, Japan.
Tamura
K
K
Kimura
B
B
Kimura
M
M
Suzuki
H
H
D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D002561:Cerebrovascular Disorders / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D013929:Thromboxane B2 / Q000096:biosynthesis / Q000097:blood*
D013929:Thromboxane B2; D001241:Aspirin