Positive inotropic agents - Dobutamine and milrinone Flashcards
Which β-adrenoceptor agonist is most commonly used for heart failure, and why is this drug preferred?
Dobutamine. It selectively stimulates cardiac contractility, and it has a lower incidence of tachycardia than other β-agonists.
Dobutamine - effects
Selective stimulation of cardiac contractility.
Decreased vascular resistance (β2).
Decreased cardiac afterload (β2).
The effects on β2-adrenoceptors augments CO.
Dobutamine - adm
Continuous IV infusion
Dobutamine - indications
Short-term management: acute heart failure, cardiogenic shock.
Does dobutamine increase survival in pts with heart failure?
No
Does dobutamine reduce symptoms of heart failure?
Yes
Dobutamine - adverse effects
Increased risk of mortality (in high doses).
Excessive vasoconstriction.
Tachyarrhythmias
Dobutamine - interactions
Adrenoceptor agonists and antagonists.
Milrinone - classification
Type 3 phosphodiesterase inhibitor.
Inodilator drug.
Milrinone - MOA
Inhibition of type 3 phosphodiesterase inhibits inactivation of cAMP. Increased levels of cAMP stimulates Ca influx. In turn, these changes causes cardiac contractility in myocytes and vasodilation in vascular smooth muscle.
Dobutamine - MOA
Stimulates formation of adenylyl cyclase which causes increases cAMP. This in turn increases Ca influx and cause cardiac contractility.
Inodilator - definition and example of such a drug
Inodilator is a drug with both positive inotropic effects and vasodilator effects. Example is milrinone
Milrinone - indications
Short-term management of heart failure that does not respond to other drgus.
Infants and children waiting for cardiac transplantation.
Myocardial stimulation.
Milrinone - administration
Intravenous
Milrinone - adverse effects
Long term: thrombocytopenia, ventricular arrhythmias, hypotension, increased mortality. Exception: children waiting for transplantations.
