The effects of piretanide on catecholamine metabolism, plasma renin activity and serum aldosterone: a double-blind pilot comparison against hydrochlorothiazide in patients with essential hypertension.

The metabolic effects of piretanide (2 x 6 mg daily) were compared with those of hydrochlorothiazide, in doses of 2 x 25 mg or 2 x 50 mg daily, in a double-blind study consisting of three parallel groups totalling 15 patients with uncomplicated essential hypertension. Thirteen patients completed the 3-months' study. At the end of the 2-week run-in period on placebo, systolic and diastolic blood pressures (lying) were 200.0 +/- 8.2/100.0 +/- 0 mmHg in the piretanide group, 185.0 +/- 17.3/102.5 +/- 5.0 mmHg in the 2 x 25 mg hydrochlorothiazide group, and 200.0 +/- 10.0/102.0 +/- 11.0 mmHg in the 2 x 50 mg hydrochlorothiazide group. After 3 months of active treatment blood pressures had decreased by 19.5%/18.8%, 7.0%/9.8% and 20.4%/18.9% in the three groups, respectively, to normotensive levels. The results showed that the antihypertensive effect of piretanide was comparable to that of 2 x 50 mg hydrochlorothiazide daly and greater than that with the lower dose hydrochlorothiazide regimen (2 x 25 mg daily). There were no differences between the three groups with regard to serum adrenaline, noradrenaline or dopamine levels. Plasma renin activity increased slightly in all three groups but, despite this, plasma aldosterone levels did not increase. Thus, no secondary hyperaldosteronism was seen. No clinically relevant changes in acid-base balance were observed. No severe side-effects occurred; the frequency of disturbing diuresis was slightly greater in the 2 x 50 mg hydrochlorothiazide group than in patients receiving piretanide.