Pharmacological analysis of the action of diuretics in the newborn pig

The effects of furosemide, ethacrynic acid, hydrochlorothiazide and amiloride on renal function of newborn piglets, 5 to 10 days old, were evaluated. Furosemide and ethacrynic acid were the most effective diuretics. Furosemide infusion at 0.5 mg/kg/hr inhibited reabsorption of 21% filtered sodium and ethacrynic acid, 1 mg/kg/hr, increased fractional sodium excretion to 29%. Hydrochlorothiazide infusion produced a milder natriuresis than furosemide or ethacrynic acid. Infusion of hydrochlorothiazide at 1.0 mg/kg/hr increased fractional sodium excretion from 0.3% during the control period to 7.2%. Furosemide, ethacrynic acid and hydrochlorothiazide each increased potassium excretion to near 20 microEq/min. amiloride (1.0 mg/kg/hr) increased fractional sodium excretion from 0.2% during control period to 2.8% during drug infusion but did not affect potassium excretion. When infused in combination with furosemide and hydrochlorothiazide, amiloride increased the natriuresis and decreased the kaliuresis of both diuretics. It is concluded that the unanesthetized piglet is a good model for renal function of immature mammals and responds to diuretics in a manner qualitatively similar to adults.