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What are the three classes of alpha receptors antagonists?
- Reversible
- irreversible
- Alpha 2 selective
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two alpha receptor blockers?
- Phentolamine: competitive, reversible
- Phenoxybenzamine: non-competitive, irreversible
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Four alpha 1 selective blockers?
- Prazosin
- Terazosin
- Doxazosin
- Tamsulosin
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What are the three classes of Beta receptor antagonists?
- Non-selective
- Beta-1 selective
- Intrinsic (partial agonist)
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What receptors do Epi and NE mainly act on ?
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Affect of alpha 2 blockage on BP?
increase sympathetic output & inc BP
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receptor constricts arterial & venous sm mm to maintain PR?
Alpha 1
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R contracts bladder, sphinctors, prostate
Alpha 1
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Adrenergic receptor causing mydriasis
Alpha 1
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Adrenergic receptor causing ejaculation
Alpha 1
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Adrenergic receptor causing nasal decongestion
Alpha 1
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Adrenergic receptor decreasing NE release
Alpha 2
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Adrenergic receptor contracting some vascular sm mm
Alpha 2
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AR increasing HR and contraction
Beta 1
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AR increasing Heart automaticity
B1
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AR increasing Renin & BP
B1
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AR relaxing bronchioles
B2
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AR dilating some blood vessels
B2
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AR increasing glyocogenolysis
B2
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AR receptor increasing lipolysis
B3
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AR increasing aqueous humor, intraocular pressure
B2
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Common ending for Alpha antagonists
-osin or -alol
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Phenoxybenzamine
only irreversible alpha antagonist, can't overcome w/ excessive NE
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What happens w/ HR after Alpha blockade?
HR and BP decrease but then there is reflex tachycardia from Baroreceptors and increased NE on B1 receptors
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What happens when you stand up and are taking an alpha blockage?
Postural hypotension = possible passing out
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What receptors does Phentolamine work on? Reversible or irreversible?
A1 & A2, reversible
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What happens if A2 is blocked?
Block NE release = harder to raise BP but baroreflex can cover
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Phentolamine side effects?
- Tachycardia
- Miosis
- Myocardial ischemia
- hyptotension
- increased urination
- stuffiness
- ** increased gastric acid (unusual)
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Althought not used often, when would you use phentolamine? (3)
- 1) Hypertensive crisis
- 2) Patients with MAO inhibition that ingest Tyramine (= large NE release)
- 3) Prevent necrosis of digits after alpha agonist or NE
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Most common use for Phenoxybenzamine?
Pheochromocytoma: tumor increasing release of NE and Epi (high HTN, tachycardia, arrhythmia)
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Prazosin receptor?
Alpha 1 blocker
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Principle functions of Prazosin?
- CO does not increase
- Less tachycardia (b/c Alpha 2 not blocked)
- baroreceptor reflex inhibited
- Hypotension
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Prazosin effect on lipids?
Decrease LDL and increase HDL
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Half life of Prazosin?
7-10 hours, problem b/c needs to be taken 2x a day
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What is the first dose phenomenon of Prazosin, Terazosin & Doxazosin?
postural hypotension = must take at bedtime so the person does not collapse
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T/F Prazosin, Terazosin & Doxazosin should be taken w/ Viagra?
F, they both decrease tone and would cause immense hypotension w/o a baro receptor effect
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Why should Terazosin and/or Doxazosin be used over Prazosin?
- Longer half life = 1 pill a day
- ** same side effects
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Drugs used to treat HTN and Benign prostatic hyperplasia?
- Prozasin
- Terazosin
- Doxazosin
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