📋 PK/PD: Inotropes - #MEDSHED
💉 Inotropes are pharmacologic agents that increase cardiac output and contractility in the setting of acute heart failure with hypoperfusion.
💉 Commonly used inotropes include dobutamine, milrinone, and isoproterenol.
💉 Dobutamine
Mechanism
B1, B2, A1 agonist
B2 agonism (peripheral vasodilation) counteracts A1 activity (vasoconstriction)
Starting Rate: 2 - 5 mcg/kg/min
Titrate to clinical response
Max Rate: 20 mcg/kg/min
Metabolism
Renal - inactive metabolites
Precautions/Considerations
Ventricular arrhythmias
Reduced efficacy in patients on chronic beta blocker therapy
💉 Milrinone
Mechanism
Phosphodiesterase inhibitor --> cAMP mediated increase ionized Ca2+ and contractile force of cardiac muscle
Starting Rate: 0.125 - 0.25 mcg/kg/min
Titrate to clinical response
Dose Range: 0.125 - 0.75 mcg/kg/minute
Metabolism
Hepatic --> excreted as unchanged drug via urine (may accumulate with renal failure)
Precautions/Considerations
Ventricular arrhythmias
Dose reduction with renal insufficiency
Hypotension
💉 Isoproterenol
Mechanism
Potent B1, B2 agonist
Dose-dependent hypotension secondary to unopposed B2 agonism
Starting Rate: 1 mcg/min
Titrate to clinical response
Dose Range: 1 - 20 mcg/min
Metabolism
Hepatic via catechol O-methyltransferase
Precautions/Considerations
Ventricular arrhythmias
Hypotension
Reduced efficacy in patients on chronic beta blocker therapy
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