ANS: Adrenergic Antagonists Flashcards
Selectivity
Prazosin, terazosin, doxazosin
A1»>A2
Selectivity
Phentolamine
Yohimbine, tolazoline
A2= A1
A2»A1
Selectivity
Labetolol and carvedilol
B1=B2>A1>A2
Selectivity
Metoprolol, atenolol, esmolol
B1»>B2
Selectivity
Propranolol, Nadolol, timolol
Butoxamine
B1=B2
B2»B1
A antagonists
CV effects
A1
Decreases PVR, lowers BP
Postural hypotension d/t failure of venous vasoconstriction on standing
A antagonists
A2
Cv effects
Inc NE release from nerves
Blocks negative feedback mechanism
A antagonists
GU FX
Eye/nose fx
Blocks in prostate and bladder cause muscle relaxation and ease micturition
Miosis, nasal congestion increased
Alpha antagonists
Bind __ to __ receptors, interfere w ability of ___ to cause a response
Selectively, alpha, catecholamines
Alpha antagonists
Competitive antagonists: 3
Bind covalently/hard to overcome: 1
Phentolamine, prazosin, yohimbine
Phenoxybenzamine
Phentolamine
Class
Effects
Nonselective alpha blocker
Vasodilation, dec BP, inc HR and CO
Phentolamine
Indic
Dose
Htn emergencies (aut dysreflex or pheochrom) 30-70 mcg/kg IV. Onset 2 min Local infilt for extravasation of sympathomimetics. 2.5-5 mg in 10 ml
Phenoxybenzamine
Binding
Activity
Effects
Covalently binds
Alpha 1 > alpha 2
Dec SVR and vasodilation
Phenoxybenzamine
Onset, e 1/2t
Indic
1 hr onset (prodrug)
Long acting, 24 hrs
Preop for pts w pheochromocytoma, can be used w raynauds
Prazosin
Indic
Action
Less what
BP control in pheochromocytoma
Selective A1 blocker (minimal A2)
Less reflexive tachycardia
Yohimbine
Action
Indic
Alpha 2 selective blocker. Inc release NE from post-synaptic neuron
Orthostatic hypotension, impotence
Terazosin and tamulosin
Indic
Action
BPH. Long acting selective Alpha 1a blocker, prostatic smooth muscle relaxation
Beta adrenergic receptor antagonists
Do what to heart, airway, vessels
Prevent sympathomimetics (competitive antagonist) from provoking response. Heart (improve 02 supply and demand). Airway (can provoke bronchospasm), vasoconstriction in skel muscles and PVD symptoms increase
Beta adrenergic receptor antagonists
Action in juxtaglomerular cells and pancreas
Prevent sympathomimetic response. Dec renin release which indirectly drops BP. Decreased stim of insulin release by epi/NE at B2 then masked symptoms of hypoglycemia at B1
Beta adrenergic antagonist
MOA
Selective binding to beta receptors (inf ino/chronotropy). Competitive and reversible inhibition w/large doses of agonists (will overcome antagonist)
Beta adrenergic agonist
Chronic use does what
Up regulates number of receptors
Beta adrenergic receptor antagonist
Derivatives of what
Substitution of
Beta agonist isoproterenol, some sympathomimetic effects
Benzene ring
Beta adrenergic receptor antagonists Non selective (which they hit, which 4 drugs)
B1 and 2
Propranolol, nadalol, timolol, pindolol
Beta adrenergic receptor antagonists
Cardioselective- which b
Which 5
Large dose does what
B1. Metoprolol, atenolol, acebutolol, betaxolol, esmolol
Overcomes selectivity
Propranolol
Action
Admin to what
Non selective, lacks sympathomimetic activity (true antagonist)
B1=B2. Admin stepwise to goal of 55-60 BPM
Propranolol
Cardiac effects
Dec HR, CO, contractility. Prominent fx w/SNS and exercise. Inc PVR and coronary vascular resistance. 02 demand lowered. Na retention d/t renal response to CO drop.
Propranolol
Pharmacokinetics
90-95% 1st pass effect (mainly oral dose). 90-95% protein bound. Metab in liver, inc 1/2t in low hepatic BF states
Propranolol
Dose
E 1/2t
Decreases clearance of
0.05 mg/kg IV or 1-10 mg, give 1 mg q5min (slow)
2-3 Hrs
Amide LAs. Pulm first pass effect of fentanyl
Timolol
Action
Indic
Non selective BB. Eye gtts can drop BP and HR and inc airway resistance
Tx glaucoma, dec IOP by decreasing produc of aqueous humor
Nadolol
Action
Metab
E 1/2 t
Non selective BB
Renal/biliary
20-40 hrs, take 1x/day
Metoprolol
Action
Selectivity
Selective beta 1 blocker
Prevents ionotropy and chronotropy
Dose related
Metoprolol
First pass effect %
Dose
E 1/2t
60%. PO 50-400 mg. IV 1-15 mg. 3-4hrs.
Atenolol
Action
E 1/2t
Most selective B1 antagonist, least CNS effects
6-7 hrs
Atenolol
Metabolism, implic
Useful for whom
Excreted via renal system, 1/2t inc markedly w renal disease
Cardiac pts w CAD
Betaxolol
Action
E 1/2t
Indic
Cardioselective B1 blocker. 11-22 hrs.
1x/day for htn. Topical for glaucoma, less bronchospasm risk than timolol.
Esmolol
Action
DOA
Selective B1 antag. Effects HR without dec BP a lot in small doses
Rapid onset and short acting
Esmolol
Dose
DOA
0.5 mg/kg IV (10-180mg IV)
50-300 mcg/kg/min gtt
<15 min
Esmolol
In doses used it doesn’t what
Occupy enough beta receptors to cause negative inotropy
Esmolol
E 1/2t
Metabolism
9 minutes**
Hydrolyzed by plasma esterases. No effects on metab of sux
SE BB
CV
PVD
A/W
Dec HR/BP/contractility
Exac PVD d/t blocking B2 vasodilation
Bronchospasm
SE BB
Metabolism
Skel muscle
Alters carb and fat metab, masks hypoglycemia if tachycardic
Distribution extracellular K, inhib K uptake into muscles
SE BB
Local anesthetics
NS
GI
May decrease BP w/LA
Fatigue and lethargy
NVD
Relative contraindications to BB: 5
AV block, CV failure, reactive airway disease, DM w/o BS monitoring, hypovolemia
Clinical uses of BB
5
Tx htn, angina, dec mortality post MI/in periop/preop for MI risk pts, suppresses tachyarrhythmias, prevents excessive SNS activity
Labetolol
Action
Selective A1 and B1 and 2 blocker. IV beta to alpha 7:1
Labetolol
Metabolism
E 1/2t
Conjugation of glucuronic acid, <5% in urine.
5-8 hrs. Prolonged in liver disease.
Labetolol
CV effects
Max BP drop when
Can cause what
Drop BP, HR, SVR, CO unaffected
5-10 min after IV admin
Orthostatic hypotension, bronchospasm, heart block, CHF, bradycardia
Labetolol
Dose
0.1-0.5 mg/kg. Usually 5 mg at a time for mild hypertension in OR
