Key result
Low-dose clonidine reduces baseline forearm vascular resistance by ~26% in older hypertensive patients.
Why the study?
The effect of clonidine treatment on cardiopulmonary baroreflex induced sympathetic activation in elderly patients with mild-to-moderate hypertension was unclear.
Does clonidine alter cardiopulmonary baroreflex induced sympathetic activation in older patients with mild-to-moderate hypertension?
Does clonidine alter cardiopulmonary baroreflex induced sympathetic activation in older patients with mild-to-moderate hypertension?
Absolute Event Rate: 35.5% vs 48%
Low-dose clonidine lowers peripheral vascular resistance in older hypertensives via peripheral mechanisms and decreased central sympathetic outflow, without impairing responses to orthostatic stress or cold pressor testing.
Clonidine may lower peripheral resistance via mixed central-peripheral effects in older hypertensives; leaves open net impact on baroreflex sympathetic control.
To determine whether clonidine treatment affects cardiopulmonary baroreflex induced sympathetic activation, we assessed the hemodynamic and hormonal responses to lower body negative pressure (LBNP) before and after 3 weeks of treatment with low-dose (0.2 mg daily) clonidine in eight older (mean age, 62 years) patients with established mild-to-moderate hypertension. Arterial pressure, heart rate (HR), forearm vascular resistance (FVR), plasma norepinephrine (NE), and renin activity (PRA) responses were assessed. Our results demonstrate that clonidine treatment had no effect on basal or stimulated PRA and plasma NE levels at baseline and during LBNP. Baseline FVR significantly decreased (48 +/- 3 to 35.5 +/- 6 U) and the FVR responses to LBNP were lower following clonidine therapy. Although baseline mean arterial pressure (MAP) and FVR as well as FVR responses to LBNP were lower after clonidine, the responses to tilt and cold pressor testing were unchanged. Thus clonidine appears to act via peripheral mechanisms, as well as by decreasing central sympathetic outflow to lower peripheral vascular resistance.
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Mohanty et al. (1986) studied Mild-to-moderate hypertension (n=8). Clonidine vs. Baseline (before treatment) was evaluated on Baseline forearm vascular resistance (FVR). Three weeks of low-dose clonidine significantly decreased baseline forearm vascular resistance from 48 to 35.5 U in older patients with mild-to-moderate hypertension.
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