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NU 600
Exam 6 - Alpha/Beta Adrenergic Agonists and Antagonists
| Question | Answer |
|---|---|
| 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
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