A comparison of the acute effects of cicletanine and bendrofluazide on urinary electrolytes and plasma potassium in essential hypertension

Summary

The acute effects on urinary electrolyte excretion and plasma potassium were compared of the anti-hypertensive dihydrofuropyridine cicletanine with the thiazide bendrofluazide in 6 patients with uncomplicated essential hypertension.

Cicletanine 50 mg or 100 mg and bendrofluazide 5 mg caused no acute decrease in blood pressure compared to placebo for 24 h after treatment. In the 24 h after a single dose of cicletanine 50 mg there was no increase in urinary sodium, potassium or volume compared to placebo.

After a single dose of cicletanine 100 mg there was a significant increase in 2 h urinary sodium excretion compared to cicletanine 50 mg and in the first 6 h a significant increase in urinary potassium compared to placebo. Urine volume did not change significantly.

After bendrofluazide 5 mg urinary sodium excretion increased significantly in the first 6 h as well as in the subsequent 18 h compared to placebo and both cicletanine 50 mg and 100 mg. Urinary potassium excretion was also significantly increased in the first 6 h after bendrofluazide compared to placebo, and urine volume significantly increased from 6 to 24 h after bendrofluazide 5 mg compared to placebo and cicletanine 100 mg. Plasma potassium was significantly reduced and plasma renin activity significantly increased 24 h after bendrofluazide 5 mg but these measurements were not significantly different from placebo after cicletanine 50 or 100 mg.

These results suggest that cicletanine 100 mg has milder acute natriuretic effects than the thiazide bendrofluazide 5 mg. In contrast cicletanine 50 mg is associated with no major acute renal effects. In view of evidence that with long-term treatment both cicletanine 50 and 100 mg have anti-hypertensive effects, these findings suggest that cicletanine may act by a different mechanism in lowering blood pressure at low and high dose.