[Plasma renin activity in essential hypertension: different short- und long-term effects of diuretics (author's...

In an acute clinical trial 12 patients with essential hypertension on a standardized sodium and potassium dietary intake were given either amilorid (10 mg daily, orally) or potassium canrenoate (200 mg daily, i.v.) for two days. Either treatment caused a significant decrease in blood pressure and an increase in plasma renin activity (PRA). The aldosterone excretion rate was elevated only in the patients receiving amilorid. Furthermore potassium retention and sodium loss were more pronounced in the amilorid group. Long-term treatment (up to 14 weeks) with amilorid (10 mg daily), spironolactone (200 mg daily) or chlortalidone (50 mg daily) significantly lowered the blood pressure of patients with essential hypertension. Plasma potassium and PRA rose significantly in patients receiving either amilorid or spironolactone. However, after three weeks of therapy the mean PRA returned to the pretreatment level in patients on amilorid while it remained persistently elevated in the spironolactone group. On the other hand, chlortalidone caused potassium loss and persistent elevation of PRA. A possible relationship between the changes in plasma potassium levels and PRA in response to diuretics is discussed.