It is known that the
angiotensin receptor blockers (ARBs) have organ protective effects in patients with
heart failure or renal impairment. Several studies have revealed that the ARB
telmisartan has an organ protective effect, but there have been few studies directly comparing the effects of
telmisartan and
calcium antagonists, since most clinical studies on
telmisartan have been conducted in treated patients or patients on combination
therapy. The present study was conducted to compare the renal and vascular protective effects of
telmisartan monotherapy and
calcium antagonist monotherapy in untreated hypertensive patients. Forty-three patients with untreated
essential hypertension were randomized to receive
amlodipine (n=22) or
telmisartan (n=21), which were respectively administered at doses of 5 mg and 40 mg once daily in the morning for 24 weeks. The patients were examined before and
after treatment to assess changes of renal function, flow-mediated dilation (a parameter of vascular endothelial function), and brachial-ankle pulse wave velocity (baPWV; a parameter of
arteriosclerosis). Before treatment, there were no significant differences in these parameters between groups. The decreases of urinary
albumin excretion and baPWV, and the increase of flow-mediated dilation were significantly greater in the
telmisartan group than the
amlodipine group, while the
antihypertensive effects were not significantly different between the two groups. In conclusion, these results suggest that
telmisartan is more effective at protecting renal function and vascular endothelial function, and at improving
arteriosclerosis than the
calcium channel blocker in patients with
essential hypertension.