Key result
Prazosin suppressed resting plasma renin activity (1.06 vs 2.14 ng/ml/h in control) but did not influence haemodynamic and hormonal responses to head-up tilt in essential hypertensive patients.
Why the study?
Does prazosin alter haemodynamic and hormonal responses to head-up tilt compared to propranolol in essential hypertensive patients?
Does prazosin alter haemodynamic and hormonal responses to head-up tilt compared to propranolol in essential hypertensive patients?
In essential hypertensive patients, prazosin effectively lowers blood pressure without blunting the normal physiological haemodynamic and hormonal responses to orthostatic stress, unlike propranolol.
May support prazosin without orthostatic blunting in hypertension; leaves open randomized comparisons to propranolol.
To evaluate the haemodynamic and hormonal effects of prazosin, head-up tilt was performed in 10 essential hypertensive patients, and these effects of prazosin on the tilt were compared with those of propranolol. The tilts were performed in control phase and the last days of treatment for two weeks with propranolol (90 mg/day) or prazosin (3-6 mg/day). Each drug significantly lowered the mean blood pressure at rest, and also suppressed its rise on the tilt. Heart rates were significantly increased by the tilt in the control phase, in the propranolol phase and in the prazosin phase. Cardiac index was significantly reduced by the tilt from 2.66 (s.e.m. = 0.22) 1/min per m2 to 2.08 (s.e.m. = 0.20) in the propranolol phase. However, there were not significant changes in other phases. Total peripheral resistance indices were significantly increased by the tilt in all three phases. Plasma renin activity and plasma aldosterone were significantly increased by the tilt from 2.14 (s.e.m. = 0.47) ng/ml per h to 2.46 (s.e.m. = 0.54) and from 50.6 (s.e.m. = 12.9) pg/ml to 74.9 (s.e.m. = 14.9) respectively, in the control phase. And they were also significantly increased from 1.06 (s.e.m. = 0.29) to 1.65 (s.e.m. = 0.45) and from 41.4 (s.e.m. = 16.3) to 54.0 (s.e.m. = 17.4) in the prazosin phase. There were no significant increases during the administration of propranolol. We observed that prazosin did not alter heart rate and cardiac index, but suppressed the renin-angiotensin system at rest. It is suggested that prazosin did not influence haemodynamic and hormonal responses to the tilt.
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Kida et al. (1984) studied Essential hypertension (n=10). Prazosin vs. Propranolol (90 mg/day) and control was evaluated on Haemodynamic and hormonal responses to head-up tilt. Prazosin suppressed resting plasma renin activity (1.06 vs 2.14 ng/ml/h in control) but did not influence haemodynamic and hormonal responses to head-up tilt in essential hypertensive patients.
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