Effect of metoclopramide therapy on arginine vasopressin excretion and renal water handling in premature infants.

The role of endogenous dopamine (DA) in regulating arginine vasopressin (AVP) release and renal water excretion was studied in 10 premature infants with a mean birth weight of 1,341 g (range 1,150-1,660 g) and a mean gestational age of 30.2 weeks (28-33 weeks), who were given metoclopramide (MTC), a specific DA antagonist. It was demonstrated that in response to MTC urine flow rate increased significantly from a basal value of 0.90 +/- 0.07 to 1.27 +/- 0.09 ml/min/1.73 m2 (mean +/- SE; p less than 0.01), urinary sodium excretion from 6.10 +/- 1.47 to 11.7 +/- 2.24 microEq/min/1.73 m2 (p less than 0.025) and osmolar clearance from 0.38 +/- 0.044 to 0.600 +/- 0.075 ml/min/1.73 m2 (p less than 0.01). MTC administration did not cause any alterations in free water clearance, whereas urinary AVP excretion fell significantly from 49.38 +/- 10.13 to 32.66 +/- 6.53 ng/min/1.73 m2 (p less than 0.05) after MTC. It is concluded that, contrary to adults, in low birth weight premature infants endogenous DA is enhancing rather than inhibiting AVP release and the MTC-induced water diuresis is independent of the fall of AVP since free water clearance remained unaltered after MTC.