Adrenergic Blockers Flashcards
Phenoxybenzamine
- irreversible alpha blocker; insurmountable blockade, forms covalent bond with receptors
- non-selective alpha 1 & 2
- only therapeutic drug that has noncompetitive antagonism
- graphically will level off (flatten on y axis) rather than move to right on x axis
Reversible alpha blockers
- Phentolamine (nonselective alpha 1 & alpha 2)
- Prazosin (alpha 1 selective)
- Terazosin (alpha 1 selective)
- Doxazosin (alpha 1 selective)
- Tamsulosin (alpha 1 selective)
- Yohimbine (alpha 2 selective)
alpha 1 selective blockers
- Prazosin
- Terazosin
- Doxazosin
- Tamsulosin (specific alpha 1A antagonist)
These are all REVERSIBLE blockers
alpha 2 selective blockers
Yohimbine
this is a REVERSIBLE blocker
Irreversible alpha blocker
phenoxybenzamine; nonselective
CVS effects of alpha blockers
- decrease PVR & BP
Convert a pressor response of Epi to a depressor response. Called Epinephrine Reversal
Cause orthostatic hypotension & reflex tachycardia, esp with nonselective blockers due to increase release of NE (due to alpha2 blockade)
adverse effects of alpha blockers
Cause orthostatic hypotension & reflex tachycardia, esp with nonselective blockers due to increase release of NE (due to alpha2 blockade)
Effects of alpha blockers on urinary bladder
- alpha 1 receptors are expressed in base of bladder & prostate & blockade–>decrease resistance to flow or urine–> used to tx urinary symptoms in men with BPH
alpha 1A subtype may be the most important subtype in mediating prostate smooth muscle contraction; Tamsulosin=specific alpha 1A antagonist
specific alpha 1A antagonist
Tamsulosin
has greater potency than other alpha 1 blockers bc alpha 1A subtype may be the most important subtype in mediating prostate smooth muscle contraction
alpha blockers used to treat pheochromocytoma
phenoxybenzamine & phentolamine
Drugs used to treat hypertension
prazosin (selective alpha1 blocker)
patient presents with decreased heart rate, sweating, malignant hypertension
Dx: pheochromocytoma
increased epi bc tumor–>
alpha blocker used to treat HTN due to clonidine withdrawal, cheese reaction
phentolamine
alpha blocker used to treat peripheral vascular disease & Raynauds
Prazosin (selective alpha1 blocker)
What’s causing urinary difficulty in BPH?
in BPH activation of alpha1A receptors in bladder trigone, prostate & prostatic urethra increases smooth muscle tone
blockade of these receptors relaxes the structures–> increases urinary flow rate & allows more complete emptying of bladder.
DO NOT REVESE THE HYPERPLASIA, only provide symptomatic relief!!
Toxicity of alpha blockers
- orthostatic hypertension
- reflex tachycardia w nonselective blockers (due to increased NE by alpha2 blockade
* *tachycardia is less common with alpha1 selective blockers
- drugs with partial agonist activity or “intrinsic sympathomimetic activity
- what is this?
- pindolol & acebutolol
2. advantage of treating patients with asthma bc the drugs are less likely to cause bronchospasm
- drugs with local anesthetic activity or ‘membrane stabilizing activity
- what is this?
- propranolol
2. the result of blockade of Na channels & can be demonstrated experimentally; no clinical effect
longterm use of an agonist has what effect on receptors
down regulation of receptors
longterm use of an antagonist has what effect on receptors
up regulation of receptors
why don’t you abruptly stop beta blockers
rebound hypertension
B1 blockers safe for asthmatics
- Betaxolol
- Esmolol
- Atenolol
- Metoprolol
“a BEAM of beta blockers”
Why is Timolol the preferred beta blocker to treat glaucoma?
when used topically in the eye some beta blockers decrease protective reflexes & increase the risk of corneal ulceration. this is ABSENT in Timolol
beta blocker used to treat pheochromocytoma
Labetalol
side effects of beta blockers
- bradycardia
- bronchospasm*
- chronic use assoc w increased lipid levels (LDL & TG)
- may mask premonitory symptoms of hypoglycemia (tachycardia, tremor, anxiety)
- CNS effects: mild sedation, vivid dreams, rarely depression
Why should beta blockers be used cautiously in patients with CHF?
because beta blockers depress myocardial contractility & excitability
premonitory symptoms of hypoglycemia
tachycardia, tremor, anxiety
can be masked by beta blockers
Beta blockers used to treat heart failure
- metoprolol
- bisoprolol
- carvedilol
beta blockers used to treat cardiac arrhythmias & MOA
Sotalol works by increasing the AV nodal refractory period
has anti arrhythmic effects involving ion channel blockade in addition to its beta blocking action
how do beta blockers treat hypertension
- decreasing CO
2. decrease renin secretion
beta blocker used during surgery as an antiarrhythmic
Esmolol; half-life = 10m
Acebutolol: 1. selectivity 2. side effects 3. uses
- beta1 selective
- sedation
- Tx Angina & HTN
atenolol: 1. selectivity 2. side effects 3. uses
- beta1 selective
- increases lipid levels
- Tx Angina & HTN
Metoprolol: 1. selectivity 2. side effects 3. uses
- Beta1 selective
- sedation & increases lipid levels
- Angina, HTN, post-MI, antiarrhythmic
Pindolol: 1. selectivity 2. side effects 3. uses
- beta 1 & 2
- partial agonist–>less likely to cause bronchospasm in patients with asthma
- HTN, Angina
epinephrine reversal
alpha blockers convert a pressor response of epinephrine to a depressor response
one of the CVS effects of alpha blockers: they cause a lowering of PVR and BP.
