Dopamine is the immediate precursor of norepinephrine.
Dopamine is a CNS neurotransmitter associated with the basal ganglia and motor control.
Cardiovascular Effects (Dopamine)
At low doses, dopamine (Intropin) interactions with D1 receptor subtype result in renal, mesenteric and coronary vasodilation.
This effect is mediated by an increase in intracellular cyclic AMP
Low doses result in enhancing glomerular filtration rates (GFR), renal blood flow, and sodium excretion.
At higher doses, dopamine increase myocardial contractility through activation of ß1 adrenergic receptors
Dopamine (Intropin) also promotes release of myocardial norepinephrine.
Dopamine (Intropin) at these higher dosages causes an increase in systolic blood and pulse pressure with little effect on diastolic pressures.
At high doses dopamine (Intropin) causes vasoconstriction by activating a1 adrenergic receptors
Therapeutic use (Dopamine)
Dopamine may be helpful in managing both cardiogenic and hypovolemic shock
Dopamine also may improve kidney function by enhancing renal blood perfusion despite low cardiac output.
Oligouria (low urine output) may be an indication of inadequate renal perfusion.
Example: dopamine may be used, in postoperative cardiopulmonary bypass patients who exhibit:
Low systemic blood-pressure
Increased atrial filling pressures
Low urinary output
Unique among catecholamines in that dopamine can simultaneously increase:
Glomerular filtration rate
Renal blood flow
Increased sodium excretion following dopamine may be due to inhibition of aldosterone secretion.
Dopamine may inhibit renal tubular solute reabsorption (suggesting that natriuresis & diuresis may occur by different mechanisms.)
Fenoldopam and dopexamine are examples of drugs that may be useful in treating heart failure by improving myocardial contractility.
Dopamine (Intropin) at higher doses increases myocardial contractility by ß1 - adrenergic receptor activation.
Dopamine IV infusion interferes with ventilatory responses to arterial hypoxemia
Dopamine (Intropin) acts as inhibitory neurotransmitter at carotid bodies and as a result one may observe an unexpected ventilation depression in patients treated with IV dopamine (Intropin), for example, to enhance myocardial contractility.
Dopexamine is a synthetic catecholamine that activates both dopaminergic and β2-adrenergic receptors.
Administration of dopexamine may result in a slight positive inotropic effect due to β2-adrenergic agonist activity; furthermore, this drug may potentiate effects of endogenous norepinephrine, secondary to reuptake blockade.
Dopexamine enhances creatinine clearance.