Adrenergic Agonists Flashcards
What can we do with these drugs to have a more profound effect?
Use with an anticholinergic
ex- B agonist to treat asthma (bronchodilation), anticholinergic (blocks bronchocontriction –> bronchodilation)
How are adrenergic agonists inactivated?
reuptake
What pathway is alpha-1 receptors coupled to?
Gq
Where are alpha-1 receptors located?
- radial muscles
- blood vessels in skin and splanchnic vessels
- GI/bladder (sphinctors)
- GI wall (relaxation)
- Salivary glands (incr secretion slightly)
Adrenergic agonists are useful for hypotension, but what what can overstim cause and why?
hemorrhage because of incr bp
Pure alpha-1 agonists cause incr bp and reflex bradycardia. Which drugs will block this reflex?
Ganglionic blockers like hexamethonium.
Where are alpha-2 receptors?
- presyn (autoregulatory)
- pancreas (inh insulin release)
- present post-syn where they cause vasoconstriction if given by IV
- CNS (stim of these decr symp outflow)
- ciliary body (inh aq humor production)
Where are B-1 receptors located?
- Heart (incr HR, incr FOC, incr conduction)
- Kidney (incr renin)
- Eye (incr aq humor production)
- Salivary glands (incr amylase secretion)
What are B receptors coupled to?
Gs
What are alpha-2 receptors coupled to?
Gi
Where are B-2 receptors located?
- ciliary body (relax- contract lens so sq humor can escape
- Bronchi (relax)
- Blood vessels in muscle (relax)
- GI/bladder wall- detrusor (relax)
- Liver (incr glu)
- Pancreas (incr insulin)
What are B-2 agonists used for clinically?
asthma and to prolong labor
Since B-2 agonists lead to incr cAMP, what does that lead to?
leads to phosphorylation, then inh myosin light chain kinase
What does it mean if the diastolic and systolic peaks in a HR are close together?
The heart is beating faster
What does it mean if the pulse width is increased?
increased strength of contraction
When does the stimulation of the eccrine sweat glands do? And where are eccrine glands located?
causes generalized sweating
-located all over the body but mostly palms and soles of feet
What happens when adrenergic get into the CNS?
- They don’t normally get in but they can with a high conc
- Cause adrenaline rush or feeling of disaster, and arousal, euphoria, anorexia
Why don’t we prefer to use symp drug for shock?
- the usual treatment is volume replacement via IV. The goal is to maintain tissue perfusion, not necessarily bp.
- so with symp drugs, too much vasoconstriction can hinder organ perfusion.
What are 3 drugs we can possible use for shock and why?
dopamine- when heart needs to be stim and there is low bp
dobutamine- if bp isn’t necessarily an issue. It has less effect on oxygen demand bc it works exclusively on FOC
NE- if bp is low
Acute hypotension
- best treatment is to lie patient down because that will incr bp, and also give fluids.
- don’t use vasoconstrictive agent if no immediate threat
What would you give for orthostatic hypotension?
alpha-1 agonist
What is heart block, and which drugs would and wouldn’t you use?
- heart block is when electrical signal causing heart to contract and pump blood is slowed or disrupted.
- epi has been used
- but pacemaker should be inserted ASAP
- isoproterenol NOT good because it incr cardiac work
Low dose epi
- B receptors
- incr HR, decr bp
Med dose epi
- B receptors, and moderate effect on alpha
- since alpha-1 incr bp and beta-2 dec bp it balances out to med incr in bp
high dose epi
- alpha-1
- response looks like norepi
What can epi cause?
-hyperglycemia bc incr glu (B2) and inh insulin (alpha-2)
What is epi used for clinically?
anaphylactic shock, cardiac arrest (B1), reduce bleeding during surgery, prolong actions of local anesthetics
What is the good coordinated effect of epi with glu?
first stim alpha-2 to inh insulin causing large amts of glu, the beta-2 cause modest incr in insulin to use the glucose.
Norepi
- doesn’t activate B2, activates alpha-1, alpha-2 and beta-1
- behaves like alpha agonist
- vasoconstriction (alpha1)- used for hypotension and shock if bp is low
- direct acting adrenergic agonist
Dopamine
D receptors- vasodilation in kidney
- inotropic effect on the heart
- used for cardiogenic and non cardiogenic shock
- direct acting adrenergic agonist
phenylepherine
- alpha-1 agonist
- cause vasoconstriction, incr bp and mydriasis
- used as nasal decongestant, mydriasis w/o cycloplegia (tropicamide will), terminate paroxysmal tach (baro reflex), hypotension
- cannot be converted to meth
methoxamine
- alpha-1 agonist
- used for orthostatic hypotension and paroxysmal tachy
clonidine
- alpha-2 agonist
- decr bp
- but incr bp at high doses
methyldopa
- alpha 2 agonist
- decr bp
dobutamine
- beta-1 agonist
- treats cardiogenic shock – if bp isn’t an issue, less effect on oxygen demand bc only B1 (no vasoconstriction_
- treats acute heart failure
- used in patients with low cardiac output basically because it stimulates the heart
- it’s an inotrope (incr strength of contraction)
albuterol
- b-2 agonist
- for asthma
salmeterol
- B2 agonist
- used for asthma and premature labor (bc B2 for uterine relaxation)
tertbutaline
- B2 agonist
- used for asthma and premature labor (bc B2 for uterine relaxation)
ritodrine
- B2 agonist
- used for asthma and premature labor (bc B2 for uterine relaxation)
metaproterenol
- b-2 agonist
- for asthma
Isoproterenol
- B1 and B2 agonist
- similar to low dose of epi
- has been used for asthma,bronchospasm, heart block and arrythmias
- not agent of choice for any application
mixed acting sympathomimetics
-stimulate the receptor but also causes NT release
ephedrine
- mixed acting adrenergic agonist
- causes release of NE
- component of herbal med
- degongestant (main), bronchospasm, hypotension
pseudoephedrine
-mixed acting adrenergic agonist
degongestant (main), bronchospasm, hypotension
-can be used to make meth
indirect acting sympathomimetics
-only work by causing the release of a NT, has no effect on the receptor
cocaine
- indirect acting adrenergic agonist
- blocks NE and dopamine reuptake
- analogues used for local anesthesia
amphetamine
- indirect acting adrenergic agonist
- stimulant
- treats ADHD and narcolepse
- incr NE and dopamine release
Tyramine
- indirect acting adrenergic agonist
- not a drug, component of food
- some drugs (MAOI) inh tyramine deg enzyme – causes hypertensive emergency and large amounts can enter CNS
