DOPAMINE-INDUCED ANTIHYPERTENSIVE EFFECTS AND PLASMA-INSULIN RISE AREBLOCKED BY METOCLOPRAMIDE IN LABETALOL TREATED PATIENTS

Eleven patients with moderate to severe hypertension were studied at t he Vargas Hospital of Caracas. The patients were pretreated with labet alol, 800 to 1200 mg/day, orally, over a period of 1 week, after which an intravenous infusion of dopamine, .5 to 3 mu g/kg/minute, was give n. Two intravenous dopamine infusions (30 minutes each) were performed before and after the injection of metoclopramide (30 mg, intravenous bolus). Two washout periods were also included before and after metocl opramide administration. Dopamine induced a decrease of blood pressure from 171.9 + 6.35/103.6 +/- 3.12 to 152.7 +/- 7.55/93.8 +/- 2.97 mm H g (P < .001) without altering heart rate, and it increased plasma insu lin levels from 8.29 +/- .70 mu U/mL to 12.09 +/- 1.83 mu U/mL (P < .0 1). Metoclopramide caused no changes of blood pressure or plasma insul in levels. Hypotensive responses and plasma insulin increases due to d opamine were blocked by metoclopramide, however. The authors conclude that a dopaminergic receptor may be involved in some cardiovascular re sponses and in modulating insulin secretion in humans.