The antihypertensive effects of doxazosin on the arterial system: changes in peripheral vascular resistance and wall tension.

Abstract

Background: Hypertension is characterized by structural and functional abnormalities that affect the entire cardiovascular system, including the large arteries. The antihypertensive efficacy of doxazosin, a selective alpha(1) antagonist, and its effects on the arterial system were investigated. Method: In our double-blind, randomized, placebo-controlled study including 30 hypertensive patients (doxazosin group: nine males, 11 females; mean age 45+/-12 years; placebo group: four males, six females; mean age 47+/-9 years), the systolic, diastolic and mean blood pressure (BP), heart rate, diameter and area of the brachial artery, peak systolic velocity, end-diastolic velocity, pulsatility index (PI), resistance index (RI), S/D (systolic velocity/diastolic velocity), flow volume, local resistance, and wall tension were recorded before and 4 h after the administration of 2 mg doxazosin or placebo. The two groups were statistically compared. Results: In the doxazosin group, systolic, diastolic and mean pressures decreased significantly (P<0.001), while heart rate remained unchanged. Local resistance (P<0.001), RI (P<0.05), PI (P<0.05), and wall tension (P<0.001) all decreased significantly, while flow volume increased significantly (P<0.05). However, no significant changes were observed in arterial diameter, surface area, peak systolic velocity, end-diastolic velocity or S/D ratio. The placebo group did not show a significant difference in any of the parameters listed above. Conclusion: The antihypertensive effect of doxazosin is accompanied by a reduction in brachial arterial wall tension that occurs without any change in arterial diameter. The lack of change in the diameter of the artery leads us to suggest different effects on other vasomotor determinants.