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NU 600

Exam 6 - Alpha/Beta Adrenergic Agonists and Antagonists

QuestionAnswer
What type of receptor is the alpha-1 adrenergic receptor? G-protein coupled receptor
What is the primary effect of alpha-1 stimulation? Vasoconstriction of smooth muscle
What types of effects occur with stimulation of alpha-1 stimulation? Arterial and venous vasoconstriction; decreased GI motility
Where are the catecholamines epinephrine, norepinephrine, and dopamine produced? Adrenal medulla **norepi also produced from sympathetic nerve fibers**
Fibers that run from the ganglion to the effector organ are called ______. post-ganglionic fibers
The neurotransmitters of post-ganglionic nerve fibers are divided into what two divisions? Sympathetic and parasympathetic
Postganglionic fibers of the parasympathetic division are primarily________. Cholinergic
What is the primary neurotransmitter of the parasympathetic nervous system? acetylcholine
The sympathetic neurons of the ANS are mostly _______. adrenergic
What are the primary neurotransmitters of the SNS? epinephrine, norepinephrine, dopamine
Fibers that run from the CNS to the ganglion are known as _______. pre-ganglionic nerve fibers
Which pre-ganglionic fibers are closer to the ganglia: sympathetic or parasympathetic? sympathetic
Identify the 4 steps of agonist binding with the alpha-1 receptor. 1)binding activates phospholipase C 2)2nd messengers are generated 3)2nd messengers cause phosphorylation of Ca++ ion channels 4) Ca++ ions facilitate the release of bound intracellular calcium at the end organ (vasoconstriction)
What effect does alpha-1 agonism have on the lungs? May result in bronchospasm
Alpha-1 receptors are found primarily in what 4 areas of the body? Heart, blood vessels, glands, gut
Identify the 4 steps of agonist binding with the alpha-2 receptor. 1)stimulation inhibits adenylate cyclase activity 2)decreased adenylate cyclase decreases cAMP levels in neurons 3)presynaptic release of neurotransmitters is blocked 4)decrease sympathetic or adrenergic outflow
What 6 things does alpha-2 agonism inhibit? Pancreatic insulin release, lipolysis, norepinephrine, Ach, contraction of sphincters of the GI tract, norepinephrine in the brain
What benefit does alpha 2 stimulation have in anesthesia? Sedation, skeletal muscle relaxation, analgesia
How does alpha-2 agonism affect platelets? Stimulates aggregation
How does alpha-2 agonism affect the GI tract and salivary glands? Relaxes GIT and decreases salivary secretions
In what two ways is the pancreas affected by alpha-2 agonism? Increased glucagon and decreased insulin release
Describe the consequences of alpha blockade of catecholamines and sympathomimetics? The heart and peripheral vasculature (alpha receptors) become relaxed, leading to orthostatic hypotension, baroreceptor mediated reflex tachy, impotence
T/F: Alpha blockers are effective in the treatment of essential HTN. False - d/t hypotensive and tachycardic (reflexive) effects
What is the difference b/w direct and indirect sympathomimetics and give examples of each. Direct: act on the alpha/beta receptors (neo, albuterol); Indirect: release endogenous catecholamines from sympathetic nerve endings (amphetamines), inhibit reuptake of catecholamines (cocaine),& inhibit enzymes that metabolize catecholamines (entacapone)
Which alpha receptors are presynaptic and which are postsynaptic? alpha1 = post; alpha2 = pre
Both phentolamine and phenoxybenzamine have both been used in the treatment of what disease? pheochromocytoma
What type of tissue is affected by phentolamine? vascular smooth muscle
What two conditions is phentolamine indicated for? pheochromocytoma and autonomic hyperreflexia
What alpha blocker can be used to reverse dental local anesthetic effects? phentolamine
What are the bolus and infusion doses of phentolamine? Bolus=30-70mcg/kg (generally 5mg bolus); Infusion=10-20mcg/kg/min (ceiling effect over 20mcg/kg/min)
Extravasation from a peripherally injected vasoconstrictor can be treated with ______ at a dose of _______. phentolamine; 2.5-5mg
What effects does phentolamine have on the heart? Increases HR, CO, may precipitate dysrhythmias
T/F: Phentolamine is useful in anginal patients. False
How do alpha-adrenergic receptor blockers affect arteries and veins, and how does this affect HR? Reduces arteriolar resistance and increases venous capacitance, which leads to reflex tachycardia
Phentolamine and phenoxybenzamine are (selective/non-selective) alpha-adrenergic blocking agents. non-selective
Which alpha-adrenergic antagonist has irreversible binding with alpha receptors? phenoxybenzamine
What type of bond is created between phenoxybenzamine and the affected alpha receptor? covalent bond
What is the major use of phenoxybenzamine? Pre-op preparation of patients w/pheochromocytoma
Why does the IV peak effect of phenoxybenzamine take up to 60min? Requires structural modification for effect
Phenoxybenzamine has a (long/short) half life of _______. long; 24hr
Phenoxybenzamine is an alpha antagonist that is a non-selective ________. haloalkylamine
Why should patients who receive phenoxybenzamine remain supine? Rx alters normal vasoconstrictive response
What should the anesthetist be prepared for after resection of a pheochromocytoma? Drop in BP
What is the PO dose of phenoxybenzamine? 0.5-1mg/kg
Prazosin causes (selective/nonselective) and (reversible/irreversible) inhibition of (alpha1/alpha2) receptors. selective; reversible; alpha1
Prazosin works (pre-synaptically/post-synaptically). post-synaptically on arterial and venous vessels
What is another indication for prazosin besides HTN? BPH
Which two alpha blockers are used to improve erectile dysfxn? phentolamine and yohimbine
Which alpha blocker is used to manage HTN from clonidine w/d? phentolamine
Alpha2 agonism results in the (inhibition/release) of norepinephrine from presynaptic vesicles. inhibition
Yohimbine is selective for what type of receptor? alpha2
Which medication was used to treat impotence 2/t diabetic and vascular issues? yohimbine (selective alpha2 blocker)
Which alpha blocker improves symptoms in asthmatics? phentolamine
Which two alpha blockers can cross the BBB? Which causes sedation/depression and which increases motor activity/anxiety? phenoxybenzamine (sedation/depression) and yohimbine (motor activity/anxiety)
Which alpha blocker is beneficial for decreasing cholesterol/LDL/triglyceride levels? prazosin
Alpha2 agonism initiates the release of the neurotransmitter ________. norepinephrine
What is the basic structure of catecholamines? Hydroxyl groups on the 3 & 4 carbon position of the organic compound catechol
Catecholamines contain an _________ ring attached to the _________ group. aromatic; amine
Where are catecholamines stored? Chromafin vesicles in the adrenal medulla
Which electrolyte is essential for the release of norepi? calcium
Alpha and beta receptors belong to what receptor family? G-protein coupled receptors
What is the function of monoamine oxidase? Metabolism of catecholamines by deamination
Where is MAO found? Sympathetic nerve fibers just outside the mitochondrial membrane
Identify the 2 types of MAO and the neurotransmitters they deaminate. MAO type A (epi and norepi); MAO type B (dopamine)
What is the end-product of norepi/epi metabolism? Of dopamine metabolism? Norepi/epi=vanylyllmandelic acid; dopamine=homovanillic acid
Besides MAO, what other enzyme metabolizes catecholamines? Catechol-O-Methyl transferase (COMT)
Where does COMT function? Methylates catecholamines in the extraneural tissue
What are epi and norepi reduced to in the COMT pathway? epi=metanephrine; norepi=normetinephrine
List the order of synthesis of catecholamines. Phenylalanine, tyrosine, dopa, dopamine, noradrenaline, adrenaline
Which second messenger is increased by beta receptor stim? cAMP
Describe the chain of events known as the "beta1 effect". cAMP stimulates protein kinase > inward Ca++ ion flux is enhanced > incr. cytoplasmic reticulum Ca++ [] > actin-myosin interaction incr. > forceful myocardial contraction
Beta2 agonism results in the relaxation of what parts of the body? bronchial, vascular, smooth muscle
How does beta2 achieve the effect of relaxation? Hyperpolarization of the cell membrane, decreasing inward Ca++ ion flux
How do competitive antagonists affect to the Dose-Response curve? Cause rightward shift
How will long-term administration of beta blockers affect beta receptors? Causes upregulation and increased numbers of beta receptors
T/F: Beta blockers increase the slope of the Dose-Response curve. False = shifts it right
What does beta adrenergic stimulation result in? Positive chronotropic, inotropic and dromotropic effects
What does a dromotropic agent affect? Speed of conduction in the AV node
75% of beta receptors in the myocardium are (beta1/beta2) and 20% are (beta1/beta2). beta1; beta2
Where are beta3 receptors primarily located and what is their role? Located in adipose tissue and involved in lipolysis and thermogenesis
What determines the agonist-antagonist activity of a beta receptor agent? Benzene ring substituents
What form is more potent for beta blockers and agonists: levorotary or dextrorotary? levorotary
Name the 4 beta blockers that affect the entire family of beta receptors. Pindolol, Inderal, Nadolol, Timolol
Name the 2 selective beta blockers for beta1 receptors. Metoprolol & atenolol
T/F: Metoprolol, atenolol, and esmolol only block beta1 receptors. False = large enough dose of esmolol can block beta2 receptors (lungs->bronchoconstriction)
Which receptors does labetalol affect? At what ratio? beta & alpha at a ratio of 7(b):1(a)
Which receptors does carvedilol antagonize? Beta1, beta2, alpha1
What is the T1/2 of carvedilol and which patients is it indicated for? T1/2=10h; CHF & HTN
Non-selective beta blockers are contraindicated in which patients? Ventricular failure, conduction abnormalities, bronchospastic dz, vasospastic angina
Agents that exhibit intrinsic sympathomimetic activity have what types of properties? Have beta antagonism and partial agonism -- better tolerated in CHF
What is the best beta blocker for patients where airway resistance is an issue and why? Acebutolol b/c it is B1 specific w/partial agonism (intrinsic sympathomimetic activity)
Which beta blocker is efficient at treating HTN in patients with bronchospastic Dz? Acebutolol
Which 4 beta blockers exhibit partial agonism? Cartelol, oxprenolol, pindolol, acebutolol
Beta blockers exhibit membrane effects that are similar to what other class of agents? Class IA antiarrhythmics (block fast Na channels)
In what ways do beta blockers mimic class IA antiarrhythmics? Prolong the action potential duration and slow conduction
Name a class IA antiarrhythmic. Quinidine
How can beta blockers benefit performers and musicians? Makes the myocardium less susceptible to endogenous and exogenous catecholamines that cause tachycardia as a result of anxiety
What important metabolic functions does Inderal interfere with? Glycogenolysis and gluconeogenesis
Which beta receptors are important contributors to glycogenolysis? beta2
(Tachycardia/Bradycardia) is a warning sign of hypoglycemia. Tachycardia
Why are non-selective beta blockers not recommended for diabetics at risk for hypoglycemia? Blunts the tachycardic warning sign of hypoglycemia and interferes w/the metabolism of glycogen
Glycogenolysis ordinarily occurs in response to what neurotransmitter? epinephrine
Beta2 stim facilitates potassium to move (into/out of) the cell. into
How does beta blockade affect potassium? Inhibits uptake of potassium into skeletal muscle (increasing plasma [])
How much can K []'s rise after giving succ in the presence of beta blockers? 0.5-1meq
Which beta blockers result in less muscle uptake of potassium? Selective B1 blockers
Which beta blocker is associated w/profound bradycardia in the presence of anesthetic gas? Timolol
Which inhaled agents are not associated w/significant additive effects of BB? Iso, sevo, des
What two things can unmask the negative inotropic effects of concomitantly administered agents? Ketamine and/or hypercarbia
What is the T1/2 of esmolol? Inderal? Nadolol? 10min; 2hr; 24hr
Which BB is highly protein bound? Inderal
How are BB primarily eliminated? via hepatorenal pathways
How long will it take for rebound effects to occur after abrupt discontinuation of chronic BB therapy? 24-48
What is the dose for an Inderal infusion? 2-3mg/hr
What does beta agonism stimulate the release of by the kidneys? Stimulates renin release from juxtaglomerulus
What is the function of renin? Convert angiotensinogen to angiotensin I
Why are BB given with vasodilating agents? The decrease in blood pressure simulates release of renin, which ultimately leads to retention of sodium and water as a compensatory mechanism. Beta blockers prevent this release of renin.
What type of BB is Inderal? Non-selective w/o agonism
True/False: Inderal blocks b1 and b2 receptors equally. True
How does inderal affect HR, contractility, and CO? Decreases all measures
What 2 things does b2 blockade increase? Peripheral and coronary vascular resistance
What effect does the prolonged systole from Inderal have on myocardial O2 demand? Increases demand but effect is offset w/lower HR
What is the PO and IV dosing of Inderal? PO 40-800mg qd; IV 0.5-1mg q5min to 0.05mg/kg
Which BB has an active metabolite? Inderal w/IV dosing
Identify 3 key points of the metabolism of Inderal. Highly protein bound; extensive 1st pass hepatic metabolism leading to unpredictable plasma []; hepatic clearance
How may Inderal influence its own clearance? It decreases CO and hepatic blood flow, therefore decreasing its clearance
True/False: Renal failure also alters the elimination 1/2 time of Inderal. False = but accumulation of metabolites may occur
What effect does Inderal have on the clearance of aminoamide local anesthetics? Decreases their clearance by decreasing hepatic blood flow, and inhibits hepatic amide metabolism
Name two amide local anesthetics whose metabolism is decreased with Inderal. Lidocaine, bupivicaine
What influence does Inderal have on the pharmacokinetics of fentanyl? What does this result in? Decreases 1st pass pulmonary uptake; results in 2-4x more fentanyl in systemic circulation after IV bolus
Nadolol has a (long/short) duration of action with a T1/2 of ______ hr. Long; 20-40
Nadolol is (selective/nonselective). nonselective
How much of nadolol is excreted unchanged in urine and bile? What implication does this have? 75%; safe to give in patients with hepatic issues but must have good renal function for clearance
What type of BB is metoprolol? Selective B1 antagonist
Metoprolol is indicated for what patient populations? HTN with chronic obstructive airway dz, PVD, hypoglycemia
How is the feature of selectivity removed from a BB? Giving large doses
Metoprolol exhibits (high/low) protein binding. low
What is the T1/2 of metoprolol? 3-4hr
Which BB is the most selective? Atenolol
Hypoglycemia is exacerbated with the administration of (selective/nonselective) BB. nonselective
What is the T1/2 of atenolol? 6hr
How is atenolol primarily metabolized? renal elimination
What type of BB is esmolol? rapid and short acting B1 selective
What is the bolus dose of esmolol? 0.5mg/kg
What is the peak and duration for esmolol? Peak=5min, Duration=10min
How is esmolol beneficial in anesthesia? Blunts SNS response to intubation and emergence
What are diseases where esmolol could be used? What is the infusion rate? Pheochromocytoma, thyrotoxicosis, cocaine intox., pregnancy induced HTN; 500mcg/kg/min
Which BB utilizes non-organ dependent pathways of metabolism? Esmolol
T/F: Succinylcholine administration prolongs the duration of action of esmolol d/t competitive metabolism with plasma cholinesterase. False = succ is plasma cholinesterase while esmolol is metabolized w/plasma esterase
What are 3 medications that can treat excess myocardial depression? Atropine, isoproterenol, dobutamine
What is the dose of atropine? 7mcg/kg IV
What Rx is used if atropine is not effective for myocardial depression? What is the dose? Isopreterenol; 2-25mcg/min
Between isoproterenol and dobutamine, which is a selective beta agonist and which is nonselective? Isopreterenol=nonselective; dobutamine=selective
What is the drug of choice for life-threatening beta blocker induced bradycardia? Glucagon
How does glucagon work to reverse myocardial depression from BB? Stimulates cAMP []'s independent of beta receptors
What benefit does CaCl serve in the treatment of excess myocardial depression 2/t BB? Reverses myocardial depression and stabilizes cell membranes
Dopamine mediates the activation of what enzyme? What does this enzyme do? Adenylate cyclase increases intracellular [] of cAMP
What second messenger is responsible for renal artery dilatation and activation of dopamine1 receptors? cAMP
Adenylate cyclase is an example of a (first/second) messenger. first
cAMP is an example of a (first/second) messenger. second
What happens to receptors with sequestration? Receptors are uncoupled and removed from the sarcolemma (down-regulation)
Give two examples of direct acting sympathomimetics. Phenylephrine and albuterol
Identify 3 ways in which indirect sympathomimetics function? Release endogenous catecholamine stores from sympathetic nerve endings (norepi); inhibit reuptake of catecholamines into the neuron (cocaine); inhibit catecholamine metabolizing enzymes (MAO/COMT) allowing for accumulation in the synaptic cleft
Name 2 medications that inhibit MAO and COMT. Parglyine and phenelzine
Which receptors do mixed drugs act on? What do they stimulate? Alpha and beta; stimulate release of catecholamines from storage vesicles
Identify a mixed acting sympathomimetic. Ephedrine
Ephedrine has a (small/large) therapeutic window. large
Alpha1 agonism results in smooth muscle ______ and pupillary _______. Contraction; dilatation
Which receptors does epinephrine interact with? Alpha 1+2, Beta1+2
What structure secretes epinephrine? adrenal medulla
How does epinephrine influence fatty acids and blood glucose? Stimulates glycogenolysis and lipolysis which increases blood glucose and free fatty acids; also inhibits beta cell release of insulin
Agonism of ______ receptors stimulates platelet aggregation. alpha
Name three actions of epinephrine in the body that makes it useful in the treatment of anaphylaxis. Stabilizes mast cell membranes, increases BP, dilates bronchioles
What is the most potent activator of alpha adrenergic receptors? How active is it compared to its precursor? epinephrine; 10x more active than norepi
Why does epi increase the likelihood of cardiac dysrhythmias? Accelerates rate of phase 4 depolarization
How does epinephrine affect potassium? Stimulates intracellular uptake of potassium
Where is norepi released? Postganglionic sympathetic nerve endings
Norepi is a potent stimulator of what two receptors? alpha1 and beta1
What receptors does norepi act on? alpha1+2, beta1
Norepi (does/does not) stimulate bronchodilation and hyperglycemia. Does not
Which catecholamine plays an important role in memory, attention, and neurocognitive functions? dopamine
Which receptors does dopamine act on? Alpha, beta, and dopaminergic
Dopamine1 receptors are (pre/post)synaptic and elicit _______ and ________ vasodilatation. post; renal, cerebral
Dopamine2 receptors are (pre/post)synaptic and inhibit what two actions? post; adenylate cyclase activity and norepi release
Nausea and vomiting may occur as a result of stim of which dopaminergic receptor? Dopamine2
Which catecholamine is associated w/the reward mechanism associated w/drug and ETOH dependence? Dopamine
Dopamine is metabolized (slowly/rapidly). rapidly
What enhances the stability of dopamine for IV administration? 5% glucose
Beta2 agonists cause relaxation in what areas of the body? Bronchial and uterine smooth muscle
Beta2 agonists are resistant to metabolism by ______, and therefore have a (long/short) duration of action. COMT; long
What is the key side effect of beta2 agonism? Tremors from skeletal muscle stimulation
How do beta2 agonists affect glucose and electrolytes? Causes hypokalemia, hypomagnesemia, hyperglycemia
What is the preferred beta2 selective agonist for acute bronchospasm? Albuterol
What is the dose for albuterol via MDI? 100mcg/puff; 2 puffs 1-5min apart NTE 20/qd
What is the duration of albuterol? 4-8hr
Where and which receptors does clonidine act on? Agonist of alpha2 receptors in the vasomotor center of the CNS-->this activity inhibits sympathetic vasomotor responses by lower HR, SBP+DBP
What are three high-risk surgeries that benefit from periop BB? Vascular, thoracic, intraperitoneal
What is the goal HR periop? 65-80bpm
Patients with what 3 diagnoses benefit from periop BB? CAD, DM, LVH
What is the BB of choice for patients with pulmonary issues? Acebutolol
Which 3 BB are indicated to reduce the risk of periop and postop MI? Esmolol, metoprolol, atenolol
What medication is useful in the treatment of rebound HTN associated w/clonidine w/d? What other conditions is it useful in treating? Labetalol; pheochromocytoma, cocaine w/d, ischemic episodes
What 3 medications are useful with intraoperative crisis? labetalol, esmolol (better d/t shorter duration vs. labetalol), phentolamine (alpha blocker)
What is the first step in treating pheochromocytoma? What is the second step? **Alpha blockade 1st** then BB 2nd
Created by: philip.truong