1. Twenty-three hypertensive patients were treated by sotalol, a pure beta-adrenergic receptor blocking agent. The drug produced a significant decrease of blood pressure in nineteen patients.
2. On average, cardiac index decreased but not significantly; heart rate decreased and stroke index increased significantly. Total peripheral resistance varied in both directions.
3. Sotalol determined a fall in plasma renin concentration (only significant in the high-renin group), a fall in plasma angiotensin II concentration and in urinary excretion rate of aldosterone accompanied by a rise in plasma potassium concentration.
4. The fall of blood pressure was not correlated with the decreases of renin and angiotensin II concentrations or excretion rate of aldosterone. However, in the placebo period plasma angiotensin II concentration was significantly correlated with total peripheral resistance; during sotalol treatment the variations of these two parameters seemed also to be correlated.
5. There was a poor correlation between decreases of cardiac output and of blood pressure; it was impossible to foresee the magnitude of the lowering of the blood pressure from the initial cardiac index.
6. The association of a diuretic with sotalol enhanced the hypotensive effect of the beta-receptor blocking drug, without significant increase of plasma renin and angiotensin II concentrations.