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Chapter 17

Chapter 17. Adrenergic Agonists. Adrenergic Agonists. Produce their effects by activating adrenergic receptors Sympathomimetic Broad spectrum of applications Congestive heart failure (CHF) Asthma Preterm labor. Mechanisms of Adrenergic Receptor Activation. Direct receptor binding

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Chapter 17

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  1. Chapter 17 Adrenergic Agonists

  2. Adrenergic Agonists • Produce their effects by activating adrenergic receptors • Sympathomimetic • Broad spectrum of applications • Congestive heart failure (CHF) • Asthma • Preterm labor

  3. Mechanisms of Adrenergic Receptor Activation • Direct receptor binding • Promotion of norepinephrine (NE) release • Inhibition of NE reuptake • Inhibition of NE inactivation

  4. Overview of Adrenergic Agonists • Therapeutic applications and adverse effects of adrenergic receptor activation • Properties of representative adrenergic agonists • Discussion of adrenergic agonists in other chapters

  5. Overview of the Adrenergic Agonists COMT = catechol-O-methyltransferase, MAO = monoamine oxidase.

  6. Fig. 17–1.  Structures of representative catecholamines and noncatecholamines.

  7. Receptor Specificity

  8. Therapeutic Applications and Adverse Effects of Adrenergic Receptor Activation • Clinical applications of alpha1 • Two responses for therapeutic use • Vasoconstriction (most common use) • Blood vessels • Skin • Viscera • Mucous membranes • Mydriasis

  9. Therapeutic Applications and Adverse Effects of Adrenergic Receptor Activation • Drugs capable of activating alpha1 receptors • Epinephrine • Norepinephrine • Phenylephrine • Dopamine

  10. Therapeutic Applications and Adverse Effects of Adrenergic Receptor Activation • Therapeutic applications of alpha1 activation • Hemostasis • Arrests bleeding via vasoconstriction • Nasal decongestion • Mucosal vasoconstriction • Adjunct to local anesthesia • Delays absorption of local anesthetic • Elevation of blood pressure • Vasoconstriction • Mydriasis • Radial muscle of the iris

  11. Therapeutic Applications and Adverse Effects of Adrenergic Receptor Activation • Adverse effects of alpha1 activation • Hypertension • Widespread vasoconstriction • Necrosis • Treatment with alpha1-blocking agent • Bradycardia • Response to vasoconstriction and elevated blood pressure (BP)

  12. Clinical Consequences of Alpha2 Activation • Alpha2 receptors in periphery • Located presynaptic ally • Activation inhibits NE release • Alpha2 in CNS • Reduction of sympathetic outflow to heart and blood vessels • Relief of severe pain

  13. Clinical Consequences of Beta1 Activation • Therapeutic applications of beta1 activation • Cardiac arrest • Not preferred drug of choice • Heart failure • Positive inotropic effect • Shock • Positive inotropic effect; increases heart rate • Atrioventricular heart block • Enhances impulse conduction through atrioventricular (AV) node

  14. Clinical Consequences of Beta1 Activation • Adverse effects of beta1 activation • Altered heart rate or rhythm • Tachycardias or dysrhythmias • Angina pectoris • Increased cardiac oxygen demand

  15. Clinical Consequences of Beta2 Activation • Therapeutic applications of beta2 activation • Asthma • Delay of preterm labor • Adverse effects of beta2 activation • Hyperglycemia • Tremor

  16. Clinical Consequences of Dopamine Receptor Activation • Activation of peripheral dopamine receptors causes dilation of the vasculature of the kidneys.

  17. Multiple Receptor Activation: Treatment of Anaphylactic Shock • Pathophysiology of anaphylaxis • Severe allergic response • Hypotension, bronchoconstriction, edema of the glottis • Treatment • Epinephrine, injected IM, is the treatment of choice for anaphylactic shock.

  18. Adrenergic Agonists • Epinephrine • Norepinephrine • Isoproterenol • Dopamine • Dobutamine • Phenylephrine • Albuterol

  19. Epinephrine • Therapeutic uses • Delays absorption of local anesthetic • Controls superficial bleeding • Elevates blood pressure • Mydriasis during ophthalmologic procedures • Overcomes AV block • Restores cardiac function in arrest • Bronchial dilation in asthma • Treatment of choice for anaphylactic shock

  20. Epinephrine • Pharmacokinetics • Absorption • Inactivation • Adverse effects • Hypertensive crisis • Dysrhythmias • Angina pectoris • Necrosis following extravasation • Hyperglycemia

  21. Epinephrine • Drug interactions • Monoamine oxidase (MAO) inhibitors • Tricyclic antidepressants • General anesthetics • Alpha-adrenergic blocking agents • Beta-adrenergic blocking agents

  22. Epinephrine • Preparations, dosage, and administration • EpiPen • IV (monitor closely) • IM • SubQ • Intracardiac—rarely used, only in asystole if IV not available • Intraspinal • Inhalation • Topical

  23. Norepinephrine • Receptor specificity • Alpha1 • Alpha2 • Beta1 • Chemical classification • Catecholamine • Therapeutic uses • Hypotensive states • Cardiac arrest

  24. Norepinephrine • Differs from epinephrine—does not activate beta2 receptors • Does not promote hyperglycemia • Cannot be given orally (MAO and COMT) • Necrosis with extravasation • Drug interactions • MAO inhibitors (MAOIs), tricyclic antidepressants (TCAs), general anesthetics, adrenergic blocking agents

  25. Isoproterenol • Receptor specificity: beta1 and beta2 • Chemical classification: catecholamine • Therapeutic uses • Cardiovascular • AV heart block, arrest • Asthma • Bronchodilation—not used anymore • Bronchospasm • During anesthesia

  26. Isoproterenol • Adverse effects • Fewer than those of NE or epinephrine (does not activate alpha-adrenergic receptors) • Tachydysrhythmias and angina pectoris • Hyperglycemia in diabetes patients • Drug interactions • MAOIs, TCAs, beta-adrenergic blockers • Preparations and administration • IV, IM, and intracardiac injections

  27. Dopamine • Receptor specificity • Low therapeutic dose: dopamine • Moderate therapeutic dose: dopamine and beta1 • Very high dose: apha1, beta1, and dopamine

  28. Dopamine • Therapeutic uses • Shock • Increases cardiac output • Increases renal perfusion • Heart failure • Increases myocardial contractility • Acute renal failure (ARF) • Was used to preserve renal function with ARF • Early ARF—failed to protect renal function, shorten stays, or reduce need for renal transplant

  29. Dopamine • Adverse effects • Tachycardia, dysrhythmias, anginal pain • Necrosis with extravasation • Drug interactions • MAOIs, TCAs, certain general anesthetics, diuretics • Preparations, dosage, and administration • Preparations: dispensed in aqueous solutions • Dosage: must be diluted • Administration: administered by IV

  30. Dobutamine • Receptor specificity: beta1 • Chemical classification: catecholamine • Actions and uses • CHF • Adverse effects • Tachycardia • Drug interactions • MAOIs, TCAs, certain general anesthetics • Preparations, dosage, and administration • Continuous IV infusion

  31. Phenylephrine • Receptor specificity • Alpha1 • Chemical classification • Noncatecholamine • Therapeutic uses • Reduces nasal congestion (locally) • Elevates blood pressure (parenterally) • Dilates pupils (eye drops) • Local anesthetic (delays absorption)

  32. Albuterol • Receptor specificity: beta2 • Chemical classification: noncatecholamine • Therapeutic uses • Asthma (selective for beta2) • Replaced isoproterenol in treatment • Adverse effects • Minimal at therapeutic doses • Will activate beta1 receptors at higher doses • Tremor most common; also tachycardia

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