If reduction in the rate of administration or discontinuation of therapy fails to lower the blood pressure, a short-acting alpha-adrenergic blocking agent may be administered.

The patient's condition should be monitored and any appropriate resuscitative measures initiated promptly.

Consider esmolol, metoprolol, or other beta-adrenergic blocking agent for cardiac dysrhythmias.

5. Pharmacological properties
5.1 Pharmacodynamic properties
Dobutamine is a selective β1-adrenergic agonist which directly stimulates β1-adrenergic receptors. Dobutamine also has mild β2-and α1-adrenergic receptor agonist effects at therapeutic doses but the main effect is cardiac stimulation (the β2- and α1- adrenergic receptor effects are balanced resulting in minimal net direct effect on systemic vasculature.

The β1-adrenergic effects of dobutamine exert a positive inotropic effect on the myocardium, resulting in increased myocardial contractility, stroke volume and cardiac output. In patients with congestive heart failure, increased left ventricular filling pressure decreases. Dobutamine, in therapeutic doses, causes a decrease in peripheral resistance but because of augmented cardiac output, systolic blood pressure and pulse pressure will be unchanged or increased. Heart rate is usually not substantially changed but coronary blood flow and myocardial oxygen consumption are usually increased.

Dobutamine facilitates atrioventricular conduction. The tendency to induce cardiac arrhythmias may be slightly less than that of dopamine (and considerably less than isoproterenol or other catecholamines). Dobutamine does not affect dopaminergic receptors (unlike dopamine) and causes no renal or mesenteric vasodilation, but urine flow may increase due to increased cardiac output.

Paediatric population

Dobutamine also exhibits inotropic effects in children, but the haemodynamic response is somewhat different than that in adults. Although cardiac output increases in children, there is a tendency for systemic vascular resistance and ventricular filling pressure to decrease less and for the heart rate and arterial blood pressure to increase more in children than in adults. Pulmonary wedge pressure may increase during infusion of dobutamine in children 12 months of age or younger.

Increases in cardiac output seems to begin at iv infusion rates as low as 1.0 micrograms/kg/minute, increases in systolic blood pressure at 2.5 micrograms/kg/minute, and heart rate changes at 5.5 micrograms/kg/minute.

The increase of dobutamine infusion rates from 10 to 20 micrograms/kg/minute usually results in further increases in cardiac output.

5.2 Pharmacokinetic properties
Dobutamine is virtually inactive after oral administration because of extensive presystemic metabolism in the gastrointestinal mucosa and liver, so it is administered by intravenous infusion. The onset of action after intravenous administration is rapid (about 2 minutes) and the peak effect occurs within 10 minutes. The mean plasma half life in patients with heart failure is 2.4 minutes. The duration of action is less than 10 minutes.

In patients with low output cardiac failure, dobutamine has a mean volume of distribution of 0.20 + 0.08Lkg-1 and a clearance of ~ 59 mL min -1 kg-1. The