A single dose study of the effects of fenoldopam and enalapril in mild hypertension.

To clarify the contribution made by the renin-angiotensin system activation to the short lived hypotensive response to fenoldopam, the haemodynamic effects of a combination of fenoldopam (100 mg) and enalapril (5 mg) were compared with fenoldopam alone, enalapril alone and placebo in a balanced, randomised, double blind, single dose study in eight hypertensive patients. Fenoldopam caused an acute fall in blood pressure which lasted approximately 3 h after dosing and was associated with a reflex tachycardia. Enalapril caused a more gradual fall in blood pressure (onset 2 h) without a reflex tachycardia. The combination of drugs produced greater reductions in blood pressure sustained for a longer period than fenoldopam alone and with a more rapid onset than enalapril alone. In combination the hypotensive effects of fenoldopam and enalapril were clearly additive and not synergistic. Activation of the renin-angiotensin system does not antagonise significantly the hypotensive effect of fenoldopam.