Adrenergic Agonists Lecture PDF Flashcards
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Sympathomimetic
An Adrenergic agonist drug that simulates sympathetic stimulation of the ANS
Sympatholytic
An adrenergic antagonist drug that inhibits sympathetic stimulation of the ANS
Inactivation of catecholamine adrenergic agonists occurs by ___ and ___ and as a result these drugs must be administered by ____
MAO, COMT, by continuous infusion
Catecholamines vs noncatecholamine drugs
Catecholamines are quickly inactivated by MAO and COMT and cannot cross BBB and therefore have minimal CNS effects, noncatecholamines are metabolized slowly and thus have longer half lives and can be delivered PO and can penetrate BBB, therefore have effect on CNS
Indirect acting adrenergic agonists and 2 examples
Tend to be noncatecholamines, cause release of NE from presynaptic terminals, inhibit its reuptake, and inhibit deactivation of it
- amphetamines
- ephedrine (which can do both)
Direct acting adrenergic agonists and 2 examples
Tend to be catecholamines, work by directly binding to and activating adrenergic receptors
- epi
- isoproterenol
Factors affecting responses to adrenergic agonists (3)
- receptor distribution and sensitivity (there are more receptors of one type depending on the tissue thus causing the predominating effect)
- receptor specificity (often at low to moderate doses and can see other activation when high doses)
- potency
Cardiovascular changes that result from adrenergic stimulation are complex because they result from not only direct stimulation of the heart but also…
….compensatory baroreceptor reflexes
Epi cardiovascular effects
- hr increase
- BP increase
- bronchodilation
Isoproterenol cardiovascular effects
- HR increase
- bronchodilation
Norepi cardiovascular effects
- HR increase
- BP increase
- no bronchodilation
Therapeutic applications of a1 stimulation (4)
- hemostasis to prevent bleeding via vasoconstriction
- nasal decongestants
- mydriasis
- elevation of BP in shock
cocaine overdose resulting in MI cause of death mechanism of action
- Cocaine acts as an adrenergic agonist and has activity on a1 receptors
- such potent activity results in coronary artery constriction (vasospasm) and lack of perfusion to the heart
Rhinitis medicamentosa
Rebound nasal congestion upon cessation of common use of decongestants
Example of a1 agonists in nasal sprays and oral decongestants
- phenylephrine
- pseudoephedrine
a1 agonist ADR’s (3)
- hypertension
- necrosis at site of administration due to microvasospasm (can be counteracted by administration of an a1 blocking agent such as phentolamine)
- bradycardia
a2 stimulation has minimal effect on ____ but larger effect on ____
PNS, CNS
Examples of a2 therapeutic agents (2)
- clondine (directly binds a2 receptors)
- a methyldopa (converted in adrenergic nerve terminals to a-methylnorepi released by adrenergic neuron and binds a2 receptors
B1 stimulation clinically relevant responses act on the…
…heart
Therapeutic applications of B1 stimulation (4)
- cardiac arrest
- heart failure
- shock
- AV heart block
B1 agonist ADR’s (2)
- altered heart rate or rhythm (tachycardia or arrhythmia)
- angina pectoris
B2 stimulation therapeutic uses (2)
- asthma
- delay of preterm labor
examples of B2 selective agents (3)
- albuterol
- levabuterol
- terbutaline (po for asthma or subQ for preterm labor)
B2 agonists ADR’s (3)
- hyperglycemia (not normally an issue unless diabetic)
- tremor
- at high doses may stimulate b1 receptors resulting in overstimulation of heart
Dopamine receptor stimulation function
-activates peripheral dopamine receptors causing dilation of mesenteric and renal vasculature to treat shock and improve renal perfusion
Pathophys of anaphylaxis
-severe allergy characterized by hypotension, bronchoconstriction, and laryngeal edema, largely due to histamine and leukotrienie release
Anaphylaxis treatment DOC and mech of action to treat hypotension, laryngeal edema, and bronchoconstriction
- Epinephrine subQ
- B1 stimulation increases cardiac output raising BP, a1 promotes vasoconstriction that can elevate BP and suppress laryngeal edema, B2 counteracts bronchoconstriction
Epinephrine (adrenalin) therapeutic uses (4)
- restore cardiac function in cardiac arrest
- produce mydriasis
- treat bronchospasm
- treat anaphylaxis
Epinephrine/norepi/isoproternol ADR’s (4)
- hypertensive crisis
- arrhythmias
- angina pectoris
- hyperglycemia
Epinephrine/norepi/isoproternol drug interactions (3)
- MAO inhibitors intensify
- tricyclic antidepressants intensify
- a/B adrenergic blocking agents inhibit action
Epi dosing ratio for oral/inhalation, subq/im, and IV/intracardiac
1: 100 oral or inhalation
1: 1000 subq, im
1: 10,000 IV or intracardiac
Norepinephrine (levophed) mech of action and therapuetic uses (2)
-only activates a1 and B1 receptors, equivalent on B1 receptors but less potent on a1 receptors
- used in hypotensive states
- cardiac arrest
Isoproternol (isuprel) mech of action and therapeutic uses (2)
-acts only on B1 and 2 receptors
- cardiac stimulant to treat AV heart block or cardiac arrest
- bronchodilator
Dopamine intropin mech of action
functions as neurotransmitter in brain and precursror of synthesis of NE in peripheral nerve endings
Dopamine (intropin) administration and therapeutic uses (3)
-IV
- Low doses to increase renal flow
- moderate doses to increase CO
- high doses to produce vasoconstriction (heart failure and shock)
Dobutamine (dobutrex) therapeutic use (1) and ADR’s (1)
- only indicated for heart failure or stress testing
- Increase AV conduction putting caution in using with afib
Phenylephrine (neosynephrine) mechanism of action and therapeutic uses (2)
-selective a1 agonist that performs vasoconstriction
- nasal decongestant
- IV infusion to provide local vasoconstriction
Ephedrine
Acts similar to epi but response is slower and lasts 10x longer but must less potent
Albuterol (ventolin) mech of action and therapuetic use (1)
- selectively stimulates B2 receptors with much less stimulation of heart than isoproternol
- asthma for relaxation of bronchial smooth muscle
Ephedrine is both a __ and ___ acting adrenergic agonist
direct, indirect
Heart primarily has ___ adrenergic receptors
B1
Blood vessels primarily have ____ adrenergic receptors
a1
Vascular beds in skeletal muscle have both a1 and B2 receptors. What will NE cause as a net response and why?
Vasodilation due to a greater number of B2 receptors and greater sensitivity
Drugs that stimulate a1 receptors (5)
- epi
- NE
- phenylephrine
- ephedrine
- dopamine
Drugs that stimulate a2 receptors (3)
- epi
- NE
- ephedrine
Drugs that stimulate B1 receptors (5)
- epi
- norepi
- isoproterenol
- dopamine
- ephedrine
Drugs that stimulate B2 receptors (4)
- epi
- isoproterenol
- terbutaline
- ephedrine
Dopamine (intropin) ADR (1) and drug interactions (2)
-vasoconstriction resulting in anginal pain and hypertension
- MAO inhibitors intensify effect
- diuretics complement effects
