AMLODIPINE INDUCES A FLOW AND PRESSURE-INDEPENDENT VASOACTIVE EFFECT ON THE BRACHIAL-ARTERY IN HYPERTENSION

1 The objectives of this study were to study the flow-dependent arteri al reactivity and pressure-independent arterial compliance of the calc ium antagonist amlodipine in hypertensive men. 2 Twenty-one hypertensi ve patients were randomized to receive 2 months treatment with placebo (n = 10) or 5-10 mg amlodipine (n = 11) once a day. Non-invasive meas urement of brachial artery mean blood pressure, diameter and flow (pul sed Doppler) and compliance (arterial mechanography and logarithmic el astic model) were obtained before and after drug administration. Vasor eactivity was studied by means of response of the brachial artery duri ng exclusion of the hand and hyperaemia post-ischaemia. 3 Compared wit h placebo, amlodipine reduced mean blood pressure (% change +/- s.e. m ean 11 +/- 1% vs 4 +/- 3%, P < 0.05), and increased aterial compliance at prevailing pressure (44 +/- 13%, vs 1 +/- 8%, P < 0.05) and at iso baric pressure (26 +/- 10% vs -3 +/- 6%, P < 0.05). A significant % ch ange increase from baseline in brachial artery diameter between placeb o and amlodipine was observed at rest (-2 +/- 3 vs 8 +/- 3%; P < 0.05) , after wrist occlusion (-3 +/- 3 vs 6 +/- 2%; P < 0.05) and during re active hyperaemia (-5 +/- 3 vs 18 +/- 5%; P < 0.05). No significant di fferences between amlodipine and placebo groups were observed in blood velocity after forearm manoeuvres before and after treatment. 4 No di fferences were observed between groups in brachial flow-dependent vaso dilation. 5 These results suggest that amlodipine induces an intrinsic pressure and flow independent effect on the large vessel tone in hype rtensive subjects.