Effect of antihypertensive therapy on plasma catecholamines in renal failure patients

The influence of antihypertensive therapy on plasma norepinephrine (NE) was examined in 58 patients with moderate chronic renal failure (CRF). Six normotensive patients not receiving antihypertensive medicines (mean serum creatinine 2.4 +/-.2 mg/dl) had a modest but significant increase in NE compared to normals in both supine (230 vs. 173 pg/ml, P greater than .05) and upright (482 vs. 377 pg/ml, P less than .05) positions. A striking increase in NE (supine 673 +/- 55, P less than .001; upright 1089 +/- 88 pg/ml, P less than .001) was observed in 34 CRF patients receiving antihypertensive regimens containing diuretic, beta-blocker, or vasodilator drugs either individually or in combination. Vasodilator therapy was associated with the highest levels of NE. In 17 further CRF patients receiving the sympathetic suppressants clonidine or methyldopa in addition to other medicines, NE values were similar to untreated, normotensive patients (supine NE 254 +/- 40 pg/ml; upright NE 474 +/- 61 pg/ml). The age, degree of renal impairment, plasma renin activity, and number and dosage of antihypertensive medicines did not account for these differences in NE. The results suggests that NE levels are modestly increased in normotensive, untreated CRF patients, but are dramatically increased by antihypertensive therapy, particularly vasodilator therapy. Clonidine or methyldopa therapy, however, is associated with significantly lower NE values in these patients despite the concomitant use of vasodilator agents.