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Adronergic Antagonists


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Undesirable side effects of drugs that antagonize NE
1. Postural Hypotension
2. Sedation/Depression
3. Increased GI Motility
4. Sodium Retention
5. Impaired Sexual Function
Irreversible antagonist of alpha 1 and 2
Length of time for irreversible blockade to develop
60-70 minutes

Lasts 3-4 days
Effects of alpha 2 blockade in phenoxybenzamine
1. enhanced reflex tachycardia
2. Enhanced GI tone and motility
3. Blockade of epi's ability to inhibt insulin secretion
Method of delivery for phenyoxybenzamine
Irritant properties dictate parenteral (however it is lipid soluble and gets into CNS)
Reversible competitive alpha 1 and 2 antagonist
Addition mechanisms found in Phentolamine over Phenyoxybenzamine
1. Vasodilation by direct action on vascular smooth muscle
2. More intense cardiac stimulation than reflex
3. Increased GI tone, motility and secretion
Phentolamine is primarily used in the OR because?
Cardiac and GI stimulation are so strong, tolerable doses have incomplete alpha blockade.
Prototype alpha 1 anatagonist and its half life
T1/2 = 3 hours
differences between prazosin and phenoxybenzamine or phentolamine
little reflex tachy
little GI stimulation
sex side effects are rare
CNS effects of drowsiness, dissiness, fatigue
This drug may cause postural hypotension with the first dose only

Should be administered lose dose at night the first time
Difference between terazosin and prazosin
Terazosin T1/2 = 12 hours
Prazosin T1/2 = 3 hours
Three therapeutic uses for alpha blockers
Essential hypertension
Urinary Retention
Drugs for essential hypertension
Prazosin and terazosin
Drugs for urinary retnetion
terazosin helps void bladder
Drugs for pheochromocytoma surgery
Pre-op Oral phenoxybenzamine
Op IV phentolamine

Cause vasodilation and increase blood volume prior to surgery
Chronic pheyochromocytoma
oral phenyoxybenzamine
non selective beta antagonists
Cardio effects of propranolol
slows all aspects of heart
decreases systolic pressure
reflexive increases in PR leading to low blood flow
low GFR
Propranolol effects on exercise tolerance in partient with angina and in normal patients
increases tolerance with angina, but decrease tolerance in normal patients
Metabolic effects of propranolol
block insulin release and metabolism on fat and muscle
Toxicity of propranolol
Extreme case of normal actions (heart failure, bronchospasm, Na and water retention, sensitization to hypoglycemia)
First pass clearance of propranolol

Half life

% protein bound

3 to 40 hours

Propranolol with T1/2 20-24 hours
2 uses of Timolol
1. Antihypertensive

2. Reduction of aqueues humor for glaucoma
non-selective beta antagonist with partial agonist activity. less withdrawl symptoms
a alpha and beta antagonist
selective beta 1 antagonist
Effects and toxicities of metoprolol
Same and propranolol without bronchiol constriction (beta 2 mediated)
beta 1 blocker with intrinsic sympathomimetic activity. t1/2 = 3 hours
beta 1 blocker with 10 min half life. used IV for critcally ill partients for rapid withdrawl if necessary.
beta 1 blocker for opthalmic uses
used for supraventricular tachycardia
beta 1 blocker with no intrinsive sympathomimetic activy
half life if 5=8 hours.
does not pentetrate CNS
Does acebutolol have intrinsic sympathomimetic activity?
Two uses for betaxolol
opthalmic use in glaucoma

Does atenolol have intrinsice sympathomimetic activity
half live of Atenolol
5-8 hours
Esmolol is approved for treatment of
Supraventricular tachycardia
T 1/2 for acebutolol
3 hours

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