The vasodilator--beta-blocker interaction--some determinants of its clinical success

Changes in plasma volume and extracellular fluid volume and after addition of hydralazine to propranolol treatment in patients with hypertension

In 16 patients with hypertension, BP could not be controlled satisfactorily by treatment with propranolol alone (mean dosage 325 mg/day). Plasma volume (PV) (T-1824) and extracellular fluid volume (ECV) (82Br-distribution space) were determined in these patients before and after the addition of hydralazine for three months (mean dosage 135 mg/day). After the addition of hydralazine, PV and ECV increased significantly, by 9% and 3%, respectively. Systolic and diastolic BPs decreased, by 15% and 13%. The mechanisms inducing fluid retention during treatment with hydralazine and the clinical significance of the problem are discussed. It is concluded that the addition of a diuretic to propranolol-hydralazine treatment is often well indicated.

Effects of carvedilol on renal function

A randomized, double-blind, placebo-controlled study was conducted to study the effects of acute and chronic administration of carvedilol in essential hypertension, with special emphasis on renal haemodynamics and function. Acute administration of a single dose of 50 mg carvedilol reduced systolic and diastolic blood pressure without inducing reflex tachycardia. Renal blood flow was preserved; accordingly, renal vascular resistance was significantly reduced. A significant reduction in the glomerular filtration rate and filtration fraction was observed. Plasma renin activity (PRA) and plasma aldosterone values were not changed. Chronic carvedilol treatment produced a significant fall in systolic and diastolic blood pressure, heart rate, PRA and plasma aldosterone. Renal blood flow, glomerular filtration rate and filtration fraction also remained unchanged; renal vascular resistance decreased significantly. It is concluded that carvedilol possesses definite antihypertensive and renal vasodilating properties, both acutely and after chronic treatment.

[Sodium nitroprusside and coronary surgery]

The anti-hypertensive properties of sodium nitroprusside have been tested in 20 patients undergoing coronary arterial surgery. Were measured the arterial pressure, heart rate, mean right atrial pressure and mean left atrial pressure. The cardiac output, systemic vascular resistance and left ventricular stroke work index were deduced. A dose of 0.8 to 3 micrograms . kg-1 . min-1 sodium nitroprusside was given at the start of surgery, and immediately afterwards. The results showed a decrease of the systemic vascular resistance, a significant drop of arterial pressure, and a significant increase of heart rate as well as a tendency for the cardiac output to fall, probably because of insufficient vascular filing. When the mean left atrial pressure was kept at 14.8 +/- 3 mmHg (1.97 +/- 0.40 kPa), and left ventricular stroke work index fell, whilst cardiac output increased. Sodium nitroprusside seemed to be useful in coronary arterial surgery if used with care.

Comparison of prazosin with hydralazine in patients receiving hydrochlorothiazide. A randomized, double-blind clinical trial

The antihypertensive efficacy and the incidence of side effects of prazosin and hydralazine were compared in a randomized, double-blind trial in 232 adult male hypertensives who could not be controlled with hydrochlorothiazide alone. There were no significant differences between regimens in the percentage of patients who attained goal blood pressure (reduction of diastolic blood pressure to below 90 mm Hg and at least 5 mm less than the baseline randomization pressure), effect on pulse rate or the incidence or reasons for terminations. Absolute reduction of blood pressure was similar for both drugs except for sitting systolic pressure at 3 and 6 months, when prazosin effected a 3.7- and 3.6-mm Hg greater response (p less than 0.05). Orthostatic dizziness (p less than 0.005), sexual dysfunction (p less than 0.02), and nightmares (p less than 0.02) were more frequent with prazosin than with hydralazine; nevertheless, patient compliance was similar for both drugs. An unexpected finding was the lack of pulse rate increase associated with hydralazine, particularly in older patients.

Changes in plasma volume and extracellular fluid volume after addition of prazosin to propranolol treatment in patients with hypertension

In fifteen patients with hypertension, inadequately controlled during treatment with propranolol alone (mean dosage 333 mg/day), plasma volume (PV) and extracellular fluid volume (ECV) were determined. After addition of prazosin for 3 months (mean dosage 9 mg/day) there was a significant increase in PV and ECV, on average 8 and 5%, respectively. The decrease in supine blood pressure, systolic as well as diastolic, was very modest, on average 11 mmHg (SD +/- 12) and 4 mmHg (SD +/- 7), respectively. The changes in standing blood pressure were more pronounced. It is assumed that the expansion of PV and ECV contributes to the inadequate blood pressure response found in the present study.