Background: Previous in vitro studies have suggested that valsartan produces significant inhibition of human platelets, probably targeting angiotensin I platelet receptors. To test whether valsartan inhibits platelet activity in mild to moderate hypertensives we conducted the randomized Valsartan Inhibits Platelets (VIP) trial.
Methods and results: Seventy-five patients with mild to moderate hypertension were randomized to valsartan 80 (n = 25), valsartan 160 (n = 29), or valsartan 320 mg/d (n = 21) for 9 weeks. Platelet function was assessed at baseline, week 5, and week 9 by aggregometry, flow cytometry, and cartridge-based analyzer. Independently of dose and duration, valsartan provided early sustained significant inhibition of adenosine diphosphate-induced platelet aggregation, decreased shear-induced activation measured with PFA-100 analyzer, and diminished expression of GP IIb/IIIa activity measured by PAC-1 antibody, GPIb (CD42b), vitronectin receptor (CD51/61), P-selectin (CD62p), lysosome-associated membrane protein (CD107a), and CD40-ligand (CD154). The antiplatelet properties of valsartan were more profound in patients with diabetes (n = 28) when compared with the nondiabetic group (n = 47). In subgroup analyses of patients with diabetes there appeared to be stronger inhibition of the platelet receptors, a significant decrease of adenosine diphosphate- and collagen-induced platelet aggregation, and more profound inhibition of GP IIb/IIIa activity.
Conclusions: In the randomized VIP trial, valsartan produced sustained inhibition of platelet aggregation and major platelet receptors. The antiplatelet properties of valsartan were not dose or time dependent. In subgroup analyses patients with diabetes with mild to moderate hypertension tended to have greater platelet inhibition, a finding which, if confirmed in future studies suggests possible additional advantages for using valsartan in this high-risk population.