Adrenergic Agonists And Antagonists Flashcards
Low doses of atropine cause ________
↑ secretion of acetylcholine because it blocks the pre synaptic M2 receptor which normally inhibits the release of acetylcholine
NE does not cause bronchodilation because the ____ receptors are mainly found in bronchial smooth muscle respond to _____
β2; epinephrine
_________ express almost exclusively α1 receptors and thus NE and epinephrine cause ______
Skin blood vessels; constriction
________ and _______ receptors are found in smooth muscles of blood vessels in skeletal muscle
β2 and α1
β2 is a vasodilator
α1 is a vasoconstrictor
Low concentration of epinephrine will cause ________ in the blood vessels supplying skeletal muscle
Vasodilation; β2 are more sensitive to epinephrine than α1 receptors are
What do you expect to see in the vessels supplying skeletal muscle when giving a high dose of epinephrine?
Vasoconstriction: both α1 and β2 receptors will be activated but the α1 response is stronger than β2
What are the classes of adrenergic agonists?
- direct acting: endogenous catecholamines, β and α agonists
- indirect acting: releasing agents, uptake inhibitors
- mixed acting
At low concentrations of epinephrine, it will activate mainly ____ and_____
β1 (found in the heart) and β2
Large doses of epinephrine cause an ↑ in BP due to:
- ↑ ventricular contraction (β1 effect)
- ↑ HR (β1 effect)
- vasoconstriction (α1 effect)
What is the effect on blood pressure (diastolic and systolic) when given a low dose of epinephrine
- diastolic pressure ↓ because: ↓ in peripheral resistance because β2 receptors are more sensitive
- systolic pressure ↑ because: ↑ cardiac contractile force (β1 effect)
- HR ↑ (β1 effect)
NO CHANGE IN MEAN BLOOD PRESSURE
The effects of epinephrine on blood pressure depends on the dose and ratio of the _____ and____ response in various vascular beds
α1; β2
Epinephrine is the drug of choice for _______
Anaphylactic shock
NE has little action on _____ receptors
β2
What are the cardiovascular effects due to NE?
- peripheral vasoconstriction (α1)
- ↑ cardiac contractility (β1)
- ↑ systolic AND diastolic pressure → ↑ BP
- baroreceptor reflex will kick in an cause BRADYCARDIA
- CO is unchanged or ↓
What is the effect of NE on cardiac output?
Unchanged or ↓ :
CO = HR x SV (SV ↑ and HR ↓)
NE is used to treat _____
Shock because it ↑ blood pressure
If atropine is given before NE, then NE will cause ___________
Tachycardia
Atropine will block the M2 receptors in the heart (↓ HR) so then no baroreceptor reflex response → ↑ HR
What receptors can dopamine activate
Dose dependent but can activate: dopamine receptors, β and α receptors
Dopamine 1 receptors > β1 receptors > α1 receptors
What is the CVS effect on LOW rate of infusion of dopamine?
Activates D1 receptors in the renal and other vascular beds:
- vasodilation
- ↑ GFR
- ↑ in renal blood flow
- ↑ in sodium excretion
With intermediate rates of infusion of dopamine, it will activate _______ receptors in the heart causing ________ and also causes release of NE from nerve terminals
β1 receptors (NE does not effect β2 receptors);
↑ cardiac output
Intermediate rate of infusion of dopamine on:
Systolic pressure
Diastolic pressure
MAP
PVR
SBP: ↑
DBP: not changed significantly because only β1 is activated
MAP: ↑
PVR: unchanged
What is the effect of HIGH rates of dopamine infusion?
- with high rates will also activate vascular α1 receptors → vasoconstriction → ↑ BP and TPR
High rates of dopamine infusion also activates _______ receptors
α1 receptors in the vasculature
For treating shock, _______ to _______ rates of dopamine infusion are used
Intermediate to high
What are some clinical uses for dopamine?
- treatment of severe CHF
- cardiogenic and septic shock
Example of a non selective β adrenergic agonist
Isoproterenol
When giving _____________ the baroreceptor reflex and the direct action of the drug is the SAME DIRECTION
Isoprotenerol
↑ in HR due to the baroreceptor reflex AND the drug
Effects of isoprotenerol on:
CO PVR Diastolic pressure Systolic pressure MAP
CO: ↑ (β1) (also ↑ in HR, force of contraction) PVR: ↓ (β2) Diastolic pressure: ↓ Systolic pressure: same or slight ↑ MAP: ↓
What is the difference between the MAP in giving low dose of epinephrine and giving isoproterenol?
MAP for low dose epinephrine is unchanged while for isoprotenerol it is ↓
What would you give someone isoproterenol for?
Emergencies to stimulate HR in bradycardia or heart block
What kind of drug is dobutamine?
Predominantly a β1 agonist but on the vascular smooth muscle it is a alpha agonist or an α1 antagonist
it is a potent inotrope
Dobutamine causes a less ↑ in _____ and less ↓ in ________ compared to isoproterenol
HR; PVR
Dobutamine causes mild vasoconstriction/vasodilation
Vasodilation
Why would you give someone dobutamien?
It is used for the dobutamine stress echocardiogram for patients who cannot run or be active. It ↑ myocardial O2 consumption like if you were exercising
Management of acute heart failure and cardiogenic shock
What are the types of β2 agonists
Short acting: albuterol
Long acting: salmeterol and formoterol
Which β2 agonist would you use to manage acute asthma symptoms?
Albuterol (short acting)
What are some adverse effects of β2 adrenergic agonists?
Restlessness, tremor, apprehension, anxiety and tachycardia
__________ is an α1 selective adrenergic agonists
Phenylephrine
What are some clinical uses for phenylephrine ?
- nasal decongestant
- used to ↑ BP In hypotension from vasodilation in shock or anesthesia
- ONLY mydriasis (dilation) WITHOUT cycloplegia (muscarinic antagonists have both mydriasis and cycloplegia)
- used to ↑ BP to terminate episodes of supraventricular tachycardia
What are the α2 selective adrenergic agonists?
- clonidine
- methyldopa
- brimonidine
________ is a partial α2 agonist and acts on the ________________ and thus reduces _________ outflow and thus _________ blood pressure
Clonidine; central presynaptic α2 adrenoreceptors; sympathetic; ↓ blood pressure
What is the net effect of clonidine on blood pressure?
↓ blood pressure because it ↓ sympathetic outflow
IV infusion of clonidine can cause _______
Acute RISE in BP due to activation of α2 receptors in the vascular smooth muscle (transient vasoconstriction)
NOT SEEN ORALLY
Which of the α2 agonists is a prodrug?
Methyldopa; it is taken up by noradrenergic neurons
What is the drug of choice for treatment of hypertension during pregnancy?
Methyldopa (↓ BP)
What is the use of bromidine?
It is a highly selective α2 agonist
Given ocularly to lower intracolar pressure in glaucoma;
Reduces aqueous humor production and ↑ outflow
What α2 agonist is given to lower intraocular pressure in glaucoma patients?
Bromidine (given topically)
What are the releasing agents of indirect acting adrenergic agonists?
- amphetamine
- methylphenidate
- tyramine
_________ is the structural analog of amphetamine
Methylphenidate
What is the MOA of cocaine
It is a uptake inhibitor that blocks monoamine reuptake and so they accumulate in the synaptic space
Atomoxetine is a selective inhibitor of _______________ and is indicated for treatment of _______
NE reuptake transporter ; ADHD
Which of the uptake inhibitors is selective?
Atomoxetine (cocaine is NOT selective)
Modafinil is used for the treatment of ____________
Narcolepsy
Modafinil is an uptake inhibitor that ↑ synaptic concentrations of _____ and ↓ concentrations of ______
↑: NE, dopamine, sertonin, and glutamate
↓ : GABA levels
What are the two mixed acting adrenergic agonists?
- ephedrine
- pseudoephedrine
What are some uses for ephedrine?
Pressor agent for spinal anesthesia
Used in myasthenia gravis
