Adrenergics Flashcards
What is an a1 specific adrenergic agonist?
phenylephrine
What is an a2 specific adrenergic agonist?
clonidine
What are the four b2 specific agonists?
(STARs for asthma)
- salmeterol
- terbutaline
- albuterol
- ritodrine
What are the b1 specific agonists?
dobutamine
What are the beta adrenergic agonists (not specific for 1 or 2)?
isoproterenol
What receptors do dopamine stimulate?
D1>b1>a1
What are the four INDIRECTLY acting adrenergic agonists?
(indirect drugs are TAME)
- tyramine
- amphetamine
- ephedrine
- methylphenidate
What are the inhibitors of neuronal uptake of biogenic amines (NE specifically)?
cocaine and tricyclic antidepressants
What are the agents that interfere with adrenergic nerve function?
methyldopa and reserpine
What are the alpha-adrenergic ANTAGONISTs?
Do they have specificity to specific a receptors?
phenoxybenzamine (a1, a2)
prazosin (a1)
tamsulosin (a1)
What are the beta-adrenergic ANTAGONISTs?
What is their specificity to b1 or b2?
propanolol (b2,b1)
metoprolol (b1)
atenolol (b1)
What adrenergic antagonist effects b and a1 receptors?
carvedilol
- What are the locations of a1 receptors?
- What is their function?
- What type of G protein?
- Agonist?
- Antagonist?
1. vasculature- contract smooth muscle- contract liver- glycogenolysis glands-secrete 3. Gq (increased Ca) 4. phenylephrine 5. prazosin
- What are the locations of a2 receptors?
- What is their function?
- What type of G protein?
- Agonist?
- Antagonist?
- presynaptic terminal- inhibit further release
pancreatic islets- inhibition of secretion - Gi/o (decrease cAMP, CA and increase K)
- clonidine
- n/a
- What are the locations of b1 receptors?
- What is their function?
- What type of G protein?
- Agonist?
- Antagonist?
- heart- increase contractility and HR
- Gs (increase AC)
- dobutamine
- metoprolol
- What are the locations of b2 receptors?
- What is their function?
- What type of G protein?
- Agonist?
- Antagonist?
1. smooth muscle- relax skeletal muscle- relax liver- glycogenolysis 3. Gs (increase AC) 4. albuterol, terbutaline 5. Experimental (propanolol, metoprolol, atenolol)
For the cardiovascular system, the most important receptors are ______for the vessels and ______ for the heart.
a1 and b2 for the vessels
b1 for the heart
What is the effect of NE on: 1. BP 2. Femoral blood flow 3. renal blood flow 4. PVR 5. myocardial contractile force 6. HR 7. CO Include a brief reason why.
- Increase (a1)
- decrease (a1)
- decrease (a1)
- increase
- increase (b1)
- brief increase (b1) then decrease (reflex)
- no change
What is the effect of epi on: 1. BP 2. Femoral blood flow 3. renal blood flow 4. PVR 5. myocardial contractile force 6. HR 7. CO Include a brief reason why.
- increase (a1) but not as much as NE because there is b2 relaxation component too
- increase because of the large b2 component
- decrease (largely a1)
- increase but not as much as NE
- increase (b1)
- increase (b1)
- increase
What is the effect of isoproterenol on: 1. BP 2. Femoral blood flow 3. renal blood flow 4. PVR 5. myocardial contractile force 6. HR 7. CO Include a brief reason why.
- decrease (b2)
- increase (b2)
- increase (b2)
- decrease
- increase (b1)
- increase (b1)
- increase to compensate for low BP
What is the effect of phenylephrine on: 1. BP 2. Femoral blood flow 3. renal blood flow 4. PVR 5. myocardial contractile force 6. HR 7. CO Include a brief reason why.
- increase (a1)
- decrease (a1)
- decrease (a1)
- increase
- same/slight decrease (no b1 stimulation)
- decrease as reflex to increased PVR
- decreased
What type of drug is phenylephrine? What are the results of giving it intravenously?
It is an a1 specific agonist. If given by IV it will vasoconstrict, increasing PVR with a rise in systolic and diastolic pressure.
The rise in pressure leads to baroreceptor reflex which will decrease HR due to increased vagal tone.
What type of drug is clonidine? What is its mode of action?
What three substances does clonodine reduce from plasma concentration?
It is an a2 specific agonist. It acts on receptors in the brainstem to turn down sympathetic signals. This results in decreased PVR in the standing position and decreased HR and stroke volume in the supine position.
It decreases renin aldosterone and NE
What type of drug is dobutamine? What are the results you would expect to see upon administration?
It is a b1 agonist.
It has positive ionotropic and chronotropic actions on the heart
What effect predominates when dobutamine is given over isoproterenol?
Isoproterenol is non-selective b agonist so it will alsp have a vasodilation effect. This will cause it to have a smaller ionotropic effect due to the decreased PVR.
Dobutamine will have a predominant ionotropic effect bc PVR will remain unchanged
Any b-adrenergic agonist comes at the cost of increased ______________.
oxygen consumption because b1 will cause the heart to pump harder and faster
What type of drug is isoproterenol?
When given IV what are the results?
B1+B2 agonist
When given by IV it will increase HR and contractility and vasodilate the vessels.
This decreases PVR especially in mesenteric, renal and skeletal vessels.
As a reflex, the vessels will reinforce the ionotropic effects on the heart
What does isoproterenol do the the systolic and diastolic BP?
Because of its b1 effects, HR and contractility will increase.
Because of b2, vasodilation renally mesenterically and in skeletal muscle will cause reflex that reinforces the increase in HR and contractility.
CO will increase as a result, so systolic BP will stay the same or rise, and because of the dilation, diastolic BP will fall
What is a negative effect of using isproterenol? Patients with _________ should especially not use this drug.
It can cause arrythmia
Patients with cardiac ischemia should not use isoproterenol because the increased work of the heart will require more oxygen consumption and it is already not getting enough
At low doses, epi effects __________ receptors the most and the responses resemble what drug?
B1 and B2 the most so the response resembles that of isoproterenol
AT higher doses of epi _________ receptors come into play and the effects of ____ and _____ predominate.
a1 come into play and the effects of a1 and b1 predominate.
You see positive ionotropic and chronotropic effects and an increased CO with elevated systolic and diastolic pressure due to vessel constriction and increased CO
What at the receptors effected by NE? What cardiovascular results would you see?
a1, b1, a2 so you would see an increase in BP (a1)
CO may be unchanged because of b1 agonistic activity
When given at low doses, dopamine effects ______ recepters located in ___________ and ___________ vascular beds.
D1 receptors in renal and mesenteric vascular beds and in the CNS
What type of G protein are D1 receptors coupled to? What response would you expect from stimulation?
Gs (increased AC) so you would expect relaxation and vasodilation
Describe the changes in action of dopamine as you move to higher and higher doses.
first, D1 with vasodilation of renal, mesenteric arterial beds and CNS activity
B1 will then stimulate HR and contractility increasing CO and systolic BP with little change in PVR
a1 is then activated which increases PVR and reduces CO
What would be a clinical situation when you would use dopamine for cardiac effects?
If there is compromised renal profusion due to circulatory shock. D1 receptors would vasodilate and increase blood flow to the kidneys
Which agonists are the most powerful bronchodilators?
B2 agonists
The effects of B2 agonists in the lungs are to _____________________ and ____________________ but they do NOT reduce____________________.
they decrease airway resistance and suppress release of inflammatory mediators but they do NOT reduce hyperresponsiveness of the bronchial
What is the benefit of using a B2 specific agonist over isoproterenol or epinephrine?
When a b2 agonist is inhaled, you get relax response from the bronchi with minimal effect of cardio system
What is the difference between albuterol and salmeterol?
Salmeterol has a longer half life (12 hours or more)
In addition to respiratory effects, what else are B2 specific agonists used for?
Since they relax smooth muscle they are used to stop premature labor by reducing contractions.
Ritodrine and terbutaline are the drugs of choice.
What kind of drug is ritodrine? What does it do?
It is a b2 agonist and is used to stop premature labor
How might b2 agonists be used to treat patients with diabetes?
b2 receptors can be found on the liver and do glycogenolysis. They also can do glycogenolysis on skeletal muscle.
B2 also enhances insulin secretion on the pancreas while a2 stops secretion (a2 predominates with epi)
What are the five main situations when phenylephrine could be used?
- local vasoconstriction
- nasal decongestion
- opthalmically
- Paroxysmal atrial tachycardia
- hypotensive states
How is phenylephrine used as a vasoconstrictor?
- It is used in local anesthesia to limit the distribution and prolong the duration of the anesthetic
- controls local bleeds
Why would you use phenylephrine to treat nasal congestion?
What is the negative side effect?
Because a1 receptors would allow the shrinkage of mucus membranes in patients with acute rhinitis.
The side effect is rebound hyperemia as well as urinary retention by constriction of trigone and sphincter