Effect of indoramin and propranolol on cardiovascular response to cold in hypertensive patients.

Immersion of the hand into ice water (cold-pressor test) in nine hypertensive subjects induced elevation of mean blood pressure, increase of vascular resistance in the extremities, decrease of blood flow in the extremities, and increase in heart rate. The preejection phase of systole was not altered. Indoramin and propranolol, each alone and together, attenuated the pressor and other cardiovascular responses. Submaximal exercise increased heart rate during placebo treatment, a response only partially attenuated by indoramin, propranolol, and their combination, but it did not induce changes in mean blood pressure during any of the treatments.

Systemic and cardiac hemodynamic interactions between clonidine and minoxidil.

We examined the hemodynamic interaction between clonidine, a centrally acting antiadrenergic drug, and minoxidil, a potent antihypertensive vasodilator in 10 inpatients with refractory or accelerated hypertension or both. Clonidine in oral doses of 150 to 900 micrograms/day decreased average mean blood pressure 18.6 mm Hg (p less than 0.01), average heart rate 16.4 bpm (p less than 0.01), limb blood flow 1.63 ml/100 gm . min (p less than 0.05), and plasma renin activity 1.13 ng/ml . hr (p less than 0.025). It also increased the pre-ejection period index 12.4 msec (p less than 0.001), but did not alter the cardiac or total peripheral resistance indices. The addition of minoxidil in oral doses of 5 to 22.5 mg/day further decreased average mean blood pressure 24.2 mm Hg (p less than 0.01), preejection period index 20.6 msec (p less than 0.01), limb vascular resistance 13.2 mm Hg/min . 100 gm/ml (p less than 0.05), and total peripheral resistance 13.3 mm Hg/min . m2/l (p less than 0.01), pre-ejection period index 20.6 msec (p less than 0.01), limb vascular resistance 13.2 mm Hg/min . 100 gm/ml (p less than 0.05), and total peripheral resistance 13.3 mm Hg/min . m2/l concluded that clonidine can be used as an alternative to beta-adrenergic blockers to counteract the increased sympathetic nervous activity minoxidil induces.