Urinary 11-dehydro-thromboxane B₂ and 2,3-dinor-6-keto-prostaglandin-F₁α in healthy post-menopausal and pre-menopausal women receiving aspirin 100 mg.

The prevalence of cardiovascular diseases in women increases sharply after menopause. In postmenopausal women, thromboxane production increases while prostacyclin decreases. Low dose aspirin reduces the production of both thromboxane and prostacyclin. The present study was an open-label clinical trial with two parallel groups of 15 premenopausal women and 15 postmenopausal women. Twenty-four hours urine was collected from each subject before and after aspirin 100 mg daily for 7 days. The concentration of thromboxane and prostacyclin was measured as their metabolites (11-dehydro-thromboxane B(2) and 2,3-dinor-6-keto-prostaglandin-F(1α)) in urine using enzyme immunoassay methods. This study showed that aspirin significantly reduced thromboxane in both groups with significantly larger percentage reduction in postmenopausal women compared to premenopausal women (73.32 vs. 61.13%, p = 0.021). This study also showed that aspirin reduced prostacyclin significantly in both groups, but the percentage reduction between the groups was not significantly different. The decrease in the ratio of 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) should be compared to assess aspirin efficacy as an antithrombotic. Calculation of the ratio of 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) before aspirin consumption was higher in postmenopausal women than in premenopausal women. The decrease in 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) ratio by aspirin was greater in postmenopausal women than in premenopausal women (1.91 vs. 0.17; p = 0.022). It was concluded that aspirin reduced thromboxane and prostacyclin significantly in each group with significant 11-dTXB(2) percentage reduction between groups and non-significant 2,3-dinor-6-keto-PGF(1α) percentage reduction between groups, but reduced the 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) ratio much larger in postmenopausal women compared to that in premenopausal women.