Human renovascular effects of dopexamine hydrochloride: a novel agonist of peripheral dopamine and beta 2-adreno-receptors.

The effects of dopexamine on the renal circulation have been examined to show whether any augmentation of renal blood flow (RBF) was secondary to the effect of the drug on cardiac output (CO) or whether it had any additional direct renal vasodilator activity. Eight male patients with mild to moderate hypertension, who were undergoing renal vein catheterization for renin estimation, were studied. Dose related increments in RBF (baseline (B) = 504 ml X min-1; after treatment (D) = 605 ml X min-1), CO (B = 5.9 l X min-1; D = 6.7 l X min-1), heart rate (B = 77 beats/min; D = 100 beats/min) and systolic blood pressure (B = 143 mmHg; D = 166 mmHg) were observed on administration of dopexamine 3 micrograms X kg-1 X min-1, with insignificant changes in diastolic blood pressure (B = 84.4 mmHg; D = 90 mmHg) and total peripheral resistance (B = 17.85; D = 17.25 Units). There was a slight but significant reduction in renal vascular resistance (B = 20.59, D = 18.75). The ratio of RBF to CO (%) confirmed that the increase in RBF due to dopexamine hydrochloride was greater that attributable to the increase in CO or perfusion pressure alone (RBF/CO B = 8.5%, D = 9%), consistent with selective renal vasodilatation. The fall in renin activity and lack of systemic vasodilatation suggest that this was a DA1-receptor mediated effect.