Dopamine and dobutamine in pediatric therapy.

Dopamine hydrochloride is widely used to increase blood pressure, cardiac output, urine output, and peripheral perfusion in neonates, infants, and older children with shock and cardiac failure. Its pharmacologic effects are dose dependent, and at low, intermediate, and high dosages include dilation of renal, mesenteric, and cerebral vasculature; inotropic response in the myocardium; and increases in peripheral and renal vascular resistance, respectively. The inotropic response is diminished in neonates compared with older children and adults due to maturational differences in norepinephrine stores. The clearance of dopamine varies widely in the pediatric population, depending on age. Its elimination half-life is approximately 2 minutes in full-term neonates and older children, and may be as long as 4-5 minutes in preterm infants. Due to immaturity of the autonomic nervous system, the drug may produce some adverse respiratory responses at high dose in neonates, the most common being tachycardia and cardiac arrhythmias. Dobutamine resembles dopamine chemically and is an analog of isoproterenol. It is relatively cardioselective at dosages used in clinical practice, with its main action being on beta 1-adrenergic receptors. Unlike dopamine, it does not have any effect on specific dopaminergic receptors. Dobutamine is used to increase cardiac output in infants and children with circulatory failure. Its elimination half-life is about 2 minutes in adults and older children. No information is available about its pharmacokinetics in neonates and infants. Adverse effects such as an increase in heart rate usually occur at high dosages.