Inhibition of platelet aggregability by losartan in essential hypertension

Most clinical events associated with hypertension have a thrombotic component. Losartan is a selective, competitive antagonist of the thromboxane A 2 receptor in experiments performed in isolated vascular strips and in human and rat platelet-enriched plasma. In this study, we investigated for the first time whether losartan at therapeutic doses has an effect on platelet aggregability and indexes of fibrinolysis in essential hypertensive subjects. Changes in the dose-response curve to platelet aggregation induced by the thrombin receptor-activating peptide SFLRRN-NH 2 were determined in 9 patients (56% men, 72% white; mean age 52.8 years) with stage I or II essential hypertension and in 9 untreated healthy volunteers. After a 4-week washout period, hypertensive subjects received 2 weeks of placebo followed by 4 weeks of losartan 50 mg/day. Both subjects and end points were blinded for treatment assignment. In addition, plasminogen activator inhibitor type 1 antigen and von Willebrand antigen were studied in all patients and controls. Four weeks of losartan produced a statistically significant (p