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59-291 Section 2, Lecture 4

Adrenergic Receptor Agonists-termed sympathomimetic

3 Groups:•Direct-acting•Indirect-acting•mixed-acting

Direct-actingSubdivided into:

-catecholamines-non catecholamines

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Catecholamines

Naturally occuring- NE, E, dopamine

Synthetic- isoproterenol and dobutamine

These are rapidly inactivated by 2 enzymes found in the gut and liver and in many other tissues: monoamine oxidase (MAO) and catechol-o-methyltransferase (COMT); low oral bioavailabilities and short t ½ therefore must be administered parenterally.

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Mechanisms and Effects

Catecholamines differ wrt affinities and specificities for the receptors

Draw relative response vs log [Catecholamine] plots for the agonists in the box.

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Sys, Dias., MeanArt. P

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Adverse effects: -excessive vasoconstriction leading to ischemia

-reduces blood flow to vital organs such as kidneys; cause excessive cardiac stimulation leading to myocardial ischemia ar arrythmias

--adrenergic agonists: hyperglycemia undesirable in diabetics

Indirect-Acting

Amphetamine- induces the

release of NE

Cocaine-prevents reuptake of NE

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Mixed-Acting: the name says it all! activate both α and receptors Ephedrine and Pseudoephedrine vasoconstriction via 1 receptors; useful as nasal decongestants; via bronchodilate

Adverse effects: tachycardia, hypertension, urinary retention