11-dehydro-thromboxane-b2 and indobufen

This study aimed to investigate the pharmacodynamic effects of indobufen and low-dose aspirin in patients with coronary atherosclerosis.. In the first phase, 218 patients with coronary atherosclerosis were randomly assigned to receive aspirin 100 mg once daily (standard dose); 100 mg once every 2 days; 100 mg once every 3 days; 50 mg twice daily; 75 mg once daily; 50 mg once daily; or indobufen 100 mg twice daily for 1 month. In the second phase, 20 healthy subjects were treated with indobufen 100 mg twice daily for 1 week followed after a 2-week washout by aspirin 100 mg once daily for 1 week. The primary outcome was arachidonic acid-induced platelet aggregation (PL. Aspirin 50 mg twice daily, 75 mg once daily, and aspirin 50 mg once daily produce antiplatelet effects that are similar to aspirin 100 mg once daily. Aspirin given less often than once daily and indobufen 100 mg twice daily do not suppress platelets as effectively as aspirin 100 mg once daily.

Topics: Aged; Aspirin; Coronary Artery Disease; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Humans; Isoindoles; Male; Middle Aged; Phenylbutyrates; Platelet Aggregation; Platelet Aggregation Inhibitors; Thromboxane B2

F2-isoprostanes are bioactive prostaglandin (PG)-like compounds that are produced from arachidonic acid through a nonenzymatic process of lipid peroxidation catalyzed by oxygen free-radicals. 8-Epi-PGF2 alpha may amplify the platelet response to agonists, circulates in plasma, and is excreted in urine. We examined the hypothesis that the formation of 8-epi-PGF2 alpha is altered in patients with hypercholesterolemia and contributes to platelet activation in this setting. Urine samples were obtained from 40 hypercholesterolemic patients and 40 age- and sex-matched control subjects for measurement of immunoreactive 8-epi-PGF2 alpha. Urinary excretion of 11-dehydro-thromboxane (TX) B2, a major metabolite of TXA2, was measured as an in vivo index of platelet activation. Low-dose aspirin, indobufen, and vitamin E were used to investigate the mechanism of formation and effects of 8-epi-PGF2 alpha on platelet activation. Urinary 8-epi-PGF2 alpha was significantly (P = .0001) higher in hypercholesterolemic patients than in control subjects: 473 +/- 305 versus 205 +/- 95 pg/mg creatinine. Its rate of excretion was inversely related to the vitamin E content of LDL and showed a positive correlation with urinary 11-dehydro-TXB2. Urinary 8-epi-PGF2 alpha was unchanged after 2-week dosing with aspirin and indobufen despite complete suppression of TX metabolite excretion. Vitamin E supplementation was associated with dose-dependent reductions in both urinary 8-epi-PGF2 alpha and 11-dehydro-TXB2 by 34% to 36% and 47% to 58% at 100 and 600 mg daily, respectively. We conclude that the in vivo formation of the F2-isoprostane 8-epi-PGF2 alpha is enhanced in the vast majority of patients with hypercholesterolemia. This provides an aspirin-insensitive mechanism possibly linking lipid peroxidation to amplification of platelet activation in the setting of hypercholesterolemia. Dose-dependent suppression of enhanced 8-epi-PGF2 alpha formation by vitamin E supplementation may contribute to the beneficial effects of antioxidant treatment.

Topics: Antioxidants; Aspirin; Cardiovascular Diseases; Cross-Sectional Studies; Cyclooxygenase Inhibitors; Dinoprost; Female; Humans; Hypercholesterolemia; Isoindoles; Lipid Peroxidation; Lipoproteins, LDL; Male; Middle Aged; Phenylbutyrates; Platelet Activation; Platelet Aggregation Inhibitors; Reactive Oxygen Species; Thromboxane B2; Vitamin E