RENAL AND NEUROHUMORAL EFFECTS OF IBOPAMINE AND METOCLOPRAMIDE IN NORMAL MAN

The effects of 100 mg ibopamine, an orally active nonselective dopamine agonist on renal haemodynamics, sodium excretion, blood pressure (BP), heart rate (HR) and neurohumoral parameters were investigated in 10 healthy volunteers, with and without metoclopramide pretreatment. A small and temporary rise of glomerular filtration rate (GFR) was found after ibopamine without but not with metoclopramide pretreatment. No differences in effective renal plasma flow (ERPF) but a small rise in sodium excretion were observed comparing ibopamine with control. Metoclopramide induced a fall in sodium excretion which was not reversed by ibopamine. Ibopamine failed to affect BP and HR and no changes of PRA or plasma aldosterone concentration (PAC) were found. Metoclopramide induced a pronounced increase of PAC which was blunted by ibopamine. Plasma and urinary catecholamines were unchanged for all study days. We conclude that ibopamine induces natriuresis probably not by the observed small and temporary renal haemodynamic effects but by direct stimulation of DA1 dopamine receptors in the proximal tubule.