Mechanism Synthetic analog of dopamine that stimulates �1-adrenoceptors and to a lesser extent �2- and �1-adrenoceptors.

�1: (Gs, ↑ cAMP) → ↑ inotropy and HR (although for unclear reasons, inotropic effects more pronounced).�2: (Gs, ↑ cAMP) → vascular smooth muscle relaxation.�1: (PIP2 cascade) → vascular smooth muscle contraction.Net effect is ↑ cardiac contractility and ↑ CO. Tends to mildly ↓ SVR due to counterbalancing of �2 and

�1 effects; overall effect on BP is variable and depends on balance between ↑ CO and ↓ SVR. Despite↑ HR, dobutamine can actually ↓ myocardial oxygen demand by ↑ inotropy and ↓ SVR.

Clinical Acute management of decompensated congestive heart failure. After �1 week of continuous therapy,downregulation of receptors will ↓ efficacy of drug.

Side Effects Arrhythmias. Possible hypotension.

Contraindic. Hypotension. Hypertrophic cardiomyopathy (worsens outflow tract obstruction).

Metabolism IV. Inactivated by COMT and MAO enzymes.

Notes

DOBUTAMINE (Dobutrex) direct sympathomimetic 4

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+

–

dobutamine

vasodilation

arterioles

heart

inotropy↑

ADREN

DOBUTAMINE

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