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 arterial reactivity and pressure-independent arterial compliance of the calcium antagonist amlodipine in hypertensive men. 2. Twenty-one hypertensive patients were randomized to receive 2 months treatment with placebo (n = 10) or 5-10 mg amlodipine (n = 11) once a day. Non-invasive measurement of brachial artery mean blood pressure, diameter and flow (pulsed Doppler) and compliance (arterial mechanography and logarithmic elastic model) were obtained before and after drug administration. Vasoreactivity was studied by means of response of the brachial artery during exclusion of the hand and hyperaemia post-ischaemia. 3. Compared with placebo, amlodipine reduced mean blood pressure (% change +/- s.e. mean 11 +/- 1% vs 4 +/- 3%, P < 0.05), and increased arterial compliance at prevailing pressure (44 +/- 13%, vs 1 +/- 8%, P < 0.05) and at isobaric pressure (26 +/- 10% vs -3 +/- 6%, P < 0.05). A significant % change increase from baseline in brachial artery diameter between placebo 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 reactive hyperaemia (-5 +/- 3 vs 18 +/- 5%; P < 0.05). No significant differences between amlodipine and placebo groups were observed in blood velocity after forearm manoeuvres before and after treatment. 4. No differences were observed between groups in brachial flow-dependent vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)