Adrenergic Agonists and Antagonists Flashcards
What are the endogenous direct-acting adrenergic catecholamines?
Epinephrine, Norepinephrine, Dopamine (affect alpha and beta receptors)
What receptors does Epinephrine act on? What cardiovascular effects does it have?
B1=B2; A1=A2; beta effects are higher affinity
CV effects: B1-positive inotrope and chronotrope -> incr. CO and SBP
-Slight reduction in systemic vasc. resistance (B2 vasodilates > alpha 1 vasoconstriction)
-Net effect: * wide pulse pressure
Clinical uses for epinephrine
- # 1 for anaphylaxis (IV)
- Cardiac arrest
- Asthma-> bronchospasm
- Local anesthetic-> alpha causes vasoconstriction -> used in combo w/ lidocaine-> vasoconstriction keeps LA in area
- Open-angle glaucoma
Epinephrine Toxicities
Palpitations, HTN, Tremor, Anxiety
-Do not give to ppl w/ hyperthyroidism or pts who are on beta blockers
What receptors does NE work on? What CV effects does it have?
A1=A2; B1»» B2
-CV effects: @ low doses negligible; increased systemic vascular resistance-> reflex drop in HR (baroreceptor effect b/c MAP=CO x TPR)
Clinical Uses for Norepinephrine
-#1 Hypotension in sepsis (IV) also cardiogenic shock
Dopamine Effects are dose dependent explain
- ***@ low doses-> Dopamine acts on DA1 Rs in kidney-> induces diuresis
- Activation of B1 receptors in the heart produces an increase in contractile force
- Increase in peripheral resistance via alpha receptors-> increases afterload -> increases HR -> arrhythmias
Clinical Uses for Dopamine (IV)
- Hypotension **
- Low CO via B1 receptors
Dopamine Toxicity:
Arrhythmia (both ventricular and supra ventricular); Wide QRS; Angina
What are the receptor-specific adrenergic agonists?
-Phenylephrine, clonidine, dobutamine, isoproteronol, albuterol
What is Phenylephrine? What does it stimulate and its effects?
- Alpha-1 adrenergic agonists
- Increased arterial vasoconstriction(increase BP)
- Decreased venous capacitance
- Reflex decrease in HR
Why do we use Phenylephrine?
- # 2 for Hypotension (IV) if can’t use NE
- Rhinitis; mydriatic
What is Clonidine? What are it’s effect?
- Alpha-2 adrenergic agonists
- Decreases SNS outflow-> decreases HR, decreases systemic vascular resistance, increases capacitance
Why do we use Clonidine?
Uses: Hypertension, anxiolytic, ADHD
Describe Clonidine Toxicity?
Dry mouth, sedation, depression, rebound HTN
What is Isoproterenol? What does it affect and how do you give it?
- Nonselective beta-adrenergic agonists
- IV only
- B1=B2 effects
- B1=increases HR, contractility, conduction velocity
- B2=decreased peripheral vascular resistance (afterload)
What is Isoproterenol used for?
Stokes-Adams attack**(Syncope due to slow or absent pulse), cardiac arrest, heart block, evaluation of tachyarrhythmia
Isoproterenol toxicity
Tachycardia, hypertension, dysrhythmia
-Increases myocardial oxygen demand
What is Dobutamine? How can we administer it?
- Beta-1 selective adrenergic agonists
- IV only
- Beta 1 selective but also (-) isomer -> some alpha
- Increased contractility > chronotropic effect
- Alpha 1 maintains peripheral resistance
What is Dobutamine used for?
-#1 drug for cardiogenic shock w/ **maintained BP
Dobutamine toxicity
Tachyarrhythmia, PVCs, hypertension
What are the alpha- blockers?
Non-selective-irreversible: Phenoxybenzamine
Non-selective-Reversible: Phentolamine
Alpha1-selective: Prazosin, Terazosin, Doxazosin, Tamulosin
What is Phenoxybenzamine?
Non-selective alpha antagonist
What effects does Phenoxybenzamine have?
- Nonselective a1 and a2 blockade (a1>a2)
- **only irreversible agent-> blockade lasts 14-48hrs
- Blocks NE reuptake at presynaptic terminals
