Platelet function in hypertension and effect of therapy

Platelet function was evaluated in 10 hypertensive and 11 normal subjects. In the placebo phase, the plasma beta thromboglobulin level (an index of platelet activation in vivo) was significantly (p less than 0.01) higher in the hypertensive than in the normal subjects; other tests of platelet function gave similar results in the two groups. After control of blood pressure with lofexidine (a centrally acting imidazoline derivative), plasma beta thromboglobulin levels decreased in 9 of the 10 hypertensive patients, but increased in one who showed no change in blood pressure. These studies suggest that enhanced platelet activation in primary hypertension may be associated with increased vascular resistance.