EFFECTS OF AMLODIPINE ON PLATELET-AGGREGATION IN HYPERTENSIVE PATIENTS - A CONTROLLED EX-VIVO STUDY

Platelet hyperactivity has been demonstrated in patients with arterial hypertension and is associated with an increase in platelet cytosolic free calcium concentration. Calcium channel blockers have been shown to decrease platelet aggregation and inhibit the mobilisation of intra platelet calcium induced by various aggregating agents. However, both platelet aggregation and intraplatelet calcium fluxes are affected onl y at drug concentrations in excess of those attained in vivo. Ex vivo investigations of the antiaggregatory effects of calcium channel block ers in healthy subjects and hypertensive patients have yielded inconsi stent results. In the present investigation, the ex vivo effects of am lodipine on platelet aggregation were evaluated in a placebo-controlle d crossover study in 10 WHO class 1 hypertensive patients. Treatment w ith amlodipine 10mg once daily for 8 days resulted in a significant de crease in arterial blood pressure, with the mean arterial pressure dec reasing from 127 +/- 4mm Hg to 110 +/- 7mm Hg (p<0.001). During the 8- day period of amlodipine treatment, platelet aggregation in whole bloo d and platelet-rich plasma was not significantly altered in comparison with baseline or placebo. In our study, however, we did not measure a ny index of platelet activation in vivo, such as plasma beta-thrombogl obulin or thromboxane B-2 generation, and the possibility that amlodip ine might exert some antiplatelet effect in vivo cannot therefore be e xcluded.