Dopamine

• Dopamine is the immediate precursor of norepinephrine.

• Dopamine is a CNS neurotransmitter associated with the basal ganglia and motor control.

• Cardiovascular Effects of Dopamine

  • Vasodilator:

    • At low doses, dopamine interactions with D₁ receptor subtype results 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.

  • Positive inotropism:

    • At higher doses, dopamine increase myocardial contractility through activation of ß₁ adrenergic receptors

    • Dopamine also promotes release of myocardial norepinephrine.

    • Dopamine at these higher dosages causes an increase in systolic blood and pulse pressure with little effect on diastolic pressures.

  • Vasopressor:

    • At high doses dopamine causes vasoconstriction by activating a₁ adrenergic receptors

• Therapeutic use of Dopamine

  • Cardiogenic shock

    • By enhancing renal perfusion despite low cardiac output. Oligouria 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

      • myocardial contractility

      • glomerular filtration rate

      • sodium excretion

      • urine output

      • renal blood flow

Category: Pharmacology Notes