Introduction
Dopamine is a sympathomimetic agent used to support blood pressure and cardiac output in patients with shock, heart failure, and hypotension. It has dose-dependent effects on beta-1 adrenergic, alpha-adrenergic, and dopaminergic receptors, providing inotropic support and vasoconstriction at higher doses.
Pharmacokinetics
Dopamine is administered intravenously and has a short half-life of 2 minutes. It is metabolized in the liver and kidneys by MAO and COMT and excreted as inactive metabolites.
Mechanism of Action
At low doses, dopamine stimulates dopaminergic receptors to increase renal perfusion. At moderate doses, it stimulates beta-1 adrenergic receptors to increase heart rate and contractility. At higher doses, it stimulates alpha-adrenergic receptors, leading to vasoconstriction.
Pharmacodynamics
Dopamine improves cardiac output and blood pressure in a dose-dependent manner. It increases myocardial contractility, heart rate, and peripheral resistance at higher doses, making it useful in various types of shock.
Adverse Effects
Tachycardia: Dopamine can cause significant increases in heart rate.
Arrhythmias: It may induce ventricular arrhythmias at higher doses.
Ischemia: Prolonged vasoconstriction can lead to tissue ischemia, particularly in extremities.
Drug Interactions
MAO inhibitors: Concurrent use may potentiate the effects of dopamine.
Beta-blockers: May reduce the positive inotropic effects of dopamine.
Dosages
Adults (Shock): 2-5 mcg/kg/min for renal effects, 5-10 mcg/kg/min for cardiac support, and 10-20 mcg/kg/min for vasopressor effects.