Adrenergic Agonists II And Antgagonists Flashcards
Affects of alpha 2 agonists on the vascular system
When give orally they accumulate int he CNS and reduce sympathetic outflow and blood pressure
Reflex tachycardia
B2 agonists effect on the vascular system
Vasodilate, decrease blood pressure
Reflex tachycardia
Effects of low doses of dopamine on the vascular system
Vasodilation of renal vessels
D1
W
What is considered the renal dose of dopamine
Low dose
Medium doses of dopamine on the vascular system
Works on B1 receptors
Stimulates HR and force
What is considered the cardiac dose of dopamine
Medium dose
High dose of dopamine on the vascular system
Acts on alpha 1
Increases BP
What are the direct acting adrenergic agonists
NE Epi Isoproterenol Phenylephrine Albuterol Mirabegron
What receptors do NE target
A1, a2, b1 agonist
Main action of NE
Increases TPR and BP, initial tachycardia followed by long term bradycardia (reflex)
What receptors do epi work on
A1,a2,b1,b2 agonist
Low dose of epi
Activate beta receptors
-lowers BP and increases HR
High doses of epi
Activate alpha receptors
-increases BP, initial tachycardia followed by lone term bradycardia
Between epi and NE, which one can increases blood pressure?
Both
Between NE and epi, which one can decrease blood pressure
Epi in low doses
What is the difference between NE and epi
epi can stimulate B2 receptors
-B2 receptors are not innervated, so NE cannot get to them, but since Epi is in the blood, it can stimulate them that way.
What receptors get targeted in low dose NE
All receptors
At what dose does epi look like NE
High doses
How do NE and epi both increases BP
Alpha one receptors
Adrenergic receptor sensitivity
B>a at low doses
A effects dominant at high doses
Dopamine receptor sensitivity
D1>B1>a1
What kind of agonist is isoproterenol
B1B2
What does isoproterenol do
Lower BP and increases HR
- looks like low dose epi
- not used clinically bc it causes arrhymias
What kind of agonist is phenylephirine
A1
What does pehnylephrine do
Increased BP but causes reflex bradycardia; mydriasis
What kind of agonist is albuteral
B2 agonist
What kind of agonist is mirabegron
B3 agonist for unirnary incontinence, some B1 effects that may increases BP
-relaxes detrusor muscle
What are the indirect acting adrenergic agonists
Amphetamine
Tyramine
Cocaine
These dont act on alpha or beta receptors but rather are taken up into the presynaptic neuron where they enhance the release of NE from synaptic vesicles
Indirect acting adrenergic agonists
-kinda do the same work as achase inhibitors but on different NT
Amphetamine
- indirect acting adrenergic agonist
- enhances NE release from adrenergic nerve terminals
- stimulates the CNS
- stimulant
Tyramine
- indirect-acting adrenergic agonist
- not a drug
- found in wine, ripe cheese, and soy sauce
- oxidized by MAO, normally has no effect on person
- if pt taking MAOIs, then these could result in hypertensive crisis
- stimulant
If someone is on an MOAI antidepressant, why should they avoid red wine, ripe cheese, and soy sauce?
These foods contain tyramine which is metabolized by MAO. If you inhibit the MAO, you wont metabolize tyramines and you will get a NE agonist effect that could cause a hypertensive crisis
-rare but fatal
Cocaine
- indirect acting adrenergic agonist
- blocks the reuptake of NE
- increased NE at synapse causes stimulant effect
- a1 and B1 agonist specifically
Why is there nasal ischemia in someone who snorts cocaine
Tons of alpha1 being stimulated by NE, causing vasoncsontriction
What is the mixed action adrenergic agonist
Ephedrine
Ephedrine
- mixed-action adrenergic agonist
- enhances release of NE from nerve terminals
- can also directly stimulate the a and B receptors
- acts like amphetamine AND epi
Characterized by being able to enhance the release of NE and stimulate the a and b receptors
Mixed action adrenergic agonists like ephedrine
Why was pseudoephredrine replaced with phenylephrine
Because people were making meth with it
What do we use for anaphylaxis
Adrenergic agonist
Epinephrine is the drug of choice
Adrenergic agonist on the eye
Alpha1 agonists like phenylephrine used topically to produce mydriasis for eye exams
Adrenergic agonist and the bronchi
B2 agonists are the drug of choice for acute asthmatic bronchoconsriction (allbuterol)
Adrenergic agonist and nasal decongestion
A1 agonists cause vasoconstriction and decrease nasal secretions (phenylephrine)
-used to be ephedrine
Using epinephrine for an anaphylactic reaction has what kind of binding?
Physiologic binding with histamine. They both bind different receptors
What are the two categories of adrenergic antagonists
B blockers
A blockers
Phenoxybenzamine
Alpha adrenergic blocker
Irreversible, long acting
Long half life bc irreversible
Non selective
Why does phenoxybenzamine have a long half life
Because it is irreversible
Which alpha adrenergic blocker as a covalent bond with a1 and a2 receptors
Phenoxybenzamine
What are the reversible, shorter acting, alpha adrenergic agonists that are selective for a1?
ZOSINS! Prazosin Doxazosin Terazosin Alfuzosin
What is ther reversible, shorter acting, nonselective adrenergic agonist?
Phentolamine
What is the reversible, shorter acting adrenergic antagonist that is selective for a2?
Mirtazapine
What happens when you block alpha 2 receptors
Can be done with mirtazapine
Increases NE, blocking negative feedback
Effects of alpha 1 blockers
ZOSINs Vasodilate Decrease BP Reflex tachycardia -this is limited because the negative feedback from the alpha2 receptors is still working
Effects of an alpha adrenergic blocker such as phentolamine
Blocks a1 and a2
Decrease BP
Reflex tachycardia
-increased tachycardia because the negative feedback from a2 is knocked out
Which will have a more severe tachycardia, phentolamine or prazosin?
Phenylalanine
A catecholamine secreting tumor of cells from the adrenal medulla
Pheochromocytoma
What does pheochromocytoma do to epi and NE
Increases both, which increases BP
Treatment for pheochromocytoma
Phenoxybezamine is useful as treatment prior to surgery or for maintenance therapy if surgery is not desired
- want to give them thsis drug because it blocks a1 (and a2 but that does not matter here).
- a zosin could be used, but we just dont do it
Primary benefit of using phenoxybenzamine for pheochromocytoma
Block of peripheral alpha 1 receptors (even though this drug also blocks a2 receptors)
How do you remember that phenoxybexamine is a treatment for pheochomocytoma?
They both have the same amount of letters and they both start with PHE
A condition caused by enlargement of the prostate gland; the urethra beceoms compressed and causes urinary obstruction
Benign prostatic hyperplasia
What is benign prostatic hyperplasia treated with
Doxazosin, tamsulosin
Why are doxazosin and tamsulosin good for treating benign prostatic hyperplasia?
Block a1 receptors in the lower urinary tract and prostate
What is the BEST drug for benign prostatic hyperplasia and why?
Tamsulosin, it targets alpha1A receptors, the predominant subtype of alpha receptor found in the prostate
What is the predominant alpha receptor in the prostate
Alpha1A
What drugs should someone with benign prostatic hyperplasia avoid
Alpha1 agonists
If someone has benign prostatic hyperplasia and hypertension, what is a good treatment plan for them
Normally we treat with tamsulosin because it targets the exact receptor we need it to (alpah1A), but if they have hypertension, and we give them any zosin, it will take care of both problems.
What drugs do we use to react hypertension
Prazosin, doxazosin (alpha blockers)
Really any zosin
What is the mechanism of zosins treating HTN
Block of peripheral a1 receptors vasodilate and lowers TPR and BP
Toxicity of alpha blockers
- ortho static (postural) hypotension
- reflex tachycardia
Orthostatic hypotension from alpha blocker toxicity
The a1 selective blockers are associated with an exaggerated orthostatic hypotensive response to the first dose, therefore the first dose is usually small
How do you avoid getting orthostatic hypotension with an alpha blocker
Take a smaller dose to begin with and work your way up
Reflex tachycardia as a slide effect of alpha blockers
More with nonsense to explain alpha blockers, could cause an angina attack
What do the names of all B blockers end in
Olol
What are the exceptions of B blockers names not ending in olol
Labetalol
Carvedilol
What are the nonspecific B blockers?
Propranolol Nadolol Timolol Pindolol Penbutolol
ALL IN 2ND HALF OF ALPHABET (N-Z)
N=NONSPECIFIC
BLOCK B1 and B2
What are the B1 specific blockers
Atenolol Betaxolol Bisoprolol Esmolol Acebutolol Metoprolol
ALL IN THE FIRST HALF OF THE ALPHABET(A-M)
Which drugs are alpha1 and B blockers?
Labetalol
Carvedilol
They are a1 and B blockers if ending in alol or ilol
Beta blockers and local anesthetic
Certain B blockers can have a local anesthetic action, except in the eye, these drugs are never used topically in the eye where anesthesi of the cornea is highly undesirable
Why do we never use topical beta blockers in the eye
Because they have local anesthetic effects, we do not want to anesthetize the cornea
Cardiovascular effects of B blockers
Block of B1 receptors on the heart causing decreased HR
Block of B2 receptor prevents vasodilation
Renal effects of B blockers
Block of B1 receptors inhibits the release of renin
Bronchoconstircion with B blockers
Block of B2 receptors on the lungs causes bronchoconstriction (problems with asthma or COPD)
Glucose metabolism and B blockers
Block of B2 receptors causes decreased glycogenolysis and lowers blood glucose
Glaucoma and B blockers
Decreases IOP by decreases aqueous humor production by the ciliary body (beta-2 block)
Adverse effects of B blockers
- hypotension, bradycardia, fatigue, drowsiness
- bronchoconstriction
- CNS depression
- increased lipids (unknown why)
Chronic presence of B blocker
Will cause the up regulation of B1 receptors on the heart and abrupt discontinuation could cause angina, HTN or arrhythmia
-always taper