Adronergic Antagonists
Terms
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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
- Phenoxybenzamine
- 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
- Phentolamine
- 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
-
Prazosin
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
-
prazosin
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
Pheochromocytoma - 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
-
Propranolol
Nadolol
Timolol
Pindolol
Labetalol - 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 -
50%
3 to 40 hours
90% - Nadolol
- 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
- Pindolol
- a alpha and beta antagonist
- Labetalol
- Metoprolol
- 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
- Acebutolol
- beta 1 blocker with 10 min half life. used IV for critcally ill partients for rapid withdrawl if necessary.
- Esmolol
- beta 1 blocker for opthalmic uses
- Betaxolol
- used for supraventricular tachycardia
- Esmolol
-
beta 1 blocker with no intrinsive sympathomimetic activy
half life if 5=8 hours.
does not pentetrate CNS - Atenolol
- Does acebutolol have intrinsic sympathomimetic activity?
- Yes
- Two uses for betaxolol
-
opthalmic use in glaucoma
antihypertensive - Does atenolol have intrinsice sympathomimetic activity
- No
- half live of Atenolol
- 5-8 hours
- Esmolol is approved for treatment of
- Supraventricular tachycardia
- T 1/2 for acebutolol
- 3 hours