Dobutamine Pharmacokinetics and Cardiovascular Responses in Critically Ill Neonates

The pharmacokinetics and pharmacodynamics of dobutamine were studied in 13 critically ill neonates requiring inotropic support. Dobutamine was administered as a constant infusion in increasing doses of 2.5, 5, and 7.5 µg/kg per minute. During dobutamine infusions, there were significant increases in cardiac output measurements above preinfusion values. There were no statistically significant changes in systolic or diastolic blood pressure or heart rate during the infusions. The mean calculated threshold value, or the minimum plasma concentration necessary for a change in cardiac output, was 39±8 ng/mL. The mean plasma clearance rate was 90±38 mL/min per kilogram and was most consistent with first-order kinetics over the range of dosages studied. Plasma catecholamine levels were unchanged during the dobutamine infusions. These data suggest that dobutamine is an effective but limited inotropic agent in the neonate. Dobutamine may be most beneficial when cardiogenic failure is present.