The effects of four months' treatment with spironolactone on systemic blood pressure, cardiac output and plasma renin activity in hypertensive patients.

The effect of spironolactone on BP, cardiac output, plasma renin activity and urinary excretion of electrolytes has been studied in 12 hypertensive patients. After 1 month of spironolactone therapy there was a significant decrease in arterial BP. Urinary sodium excretion was significantly decreased and plasma renin activity increased. After four months of spironolactone therapy there was no further decrease in arterial BP. Cardiac output, heart rate and stroke volume were unchanged in the supine position, but the calculated total peripheral vascular resistance (TPVR) was reduced, indicating that the lower BP was mainly a result of dilatation of the resistance vessels. During exercise there was still a significant decrease in arterial BP but this was related to a decrease in both cardiac output and TPVR.