The hypernoradrenergic state in vasodilator drug-treated hypertensive patients: effect of clonidine

We studied 11 previously refractory hypertensive subjects who were treated with minoxidil, propranolol, and diuretics for 2--7 years. During this time 70 random blood samples were collected in the supine position and analyzed for plasma norepinephrine (PNE) and plasma renin activity (PRA). The mean PNE was 546 pg/ml (normal mean +/- SE, 173 +/- 10) and was reciprocally related to log PRA. To determine if this elevated PNE would respond to clonidine, 5 of the patients were admitted to the General Clinical Research Center for administration of placebo and later of clonidine (0.1 or 0.2 mg). A single dose of clonidine suppressed PNE (p less than 0.01) and lowered mean blood pressure (p less than 0.02) for 12 hr. The PRA was not altered significantly by clonidine. Thus, high PNE in these treated patients can be suppressed by clonidine, and this suppression of PNE and blood pressure occurs without alteration of PRA.