1 59-291 section 2, lecture 4 adrenergic receptor agonists -termed sympathomimetic 3 groups:...
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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