Chapter 13 Drugs Affecting Adrenergic Function

1. Chapter 13Drugs Affecting Adrenergic Function

2. Question • The sympathetic nervous system produces what type of response? • A. Adrenergic • B. Antiadrenergic • C. Cholinergic • D. Anticholinergic

3. Answer • The sympathetic nervous system produces what type of response? • A. Adrenergic • The sympathetic nervous system produces an adrenergic response, and the parasympathetic nervous system produces a cholinergic response.

4. Chapter Summary • The nervous system is divided into two main branches, the central nervous system (CNS) and the peripheral nervous system (PNS). • The efferent division has neurons that carry signals away from the brain and spinal cord to the periphery. • The afferent division contains neurons that carry impulses from the periphery to the CNS. • The autonomic nervous system (ANS) is in turn subdivided into the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNS).

5. Function of the Autonomic Nervous System • The ANS has been identified as an involuntary system responsible for the control of smooth muscle. • The actual connection between neurons and effector organs or tissues relies on neurotransmitters and synaptic transmission. • The neurotransmitters in the ANS include acetylcholine (ACh), norepinephrine (NE), and epinephrine (Epi). • Synaptic transmission initially involves the synthesis of neurotransmitters in the nerve terminal. • In the SNS, preganglionic transmission is mediated by ACh, whereas postganglionic transmission is mediated by NE.

6. SNS and PSNS Effects on the Body

7. Adrenergic Receptors • In the SNS, there are several types of adrenergic receptors, including alpha-adrenergic and beta-adrenergic receptors. • Another type of receptor, the dopaminergic receptor, is related to adrenergic receptors in that dopamine is the precursor to NE. • Alpha and beta receptors are located throughtout the body. • Alpha-1 and beta-1 receptors respond to epinephrine, NE, and dopamine. • Alpha-2 receptors respond to epinephrine and NE. • Beta-2 receptors respond only to epinephrine.

8. Pathophysiology • The therapeutic uses of sympathetic drugs are related to providing extra-adrenergic stimulation or blockade of normal ANS functioning. • One of the most frequent indications for adrenergic agonist drugs is shock. • Shock is the result of inadequate tissue perfusion, leaving the cells without the oxygen and nutrients they need to function normally and survive.

9. Adrenergic Agonists • Adrenergic agonists are drugs that mimic the action of the SNS. • They exert their effects by direct or indirect stimulation of adrenergic receptors. • These drugs are generally divided into two groups: catecholamines and noncatecholamines. • Adrenergic agonists are also classified according to their selectivity. • Nonselective adrenergic agonists stimulate both alpha and beta receptors. • Prototype drug nonselective adrenergic agonist: epinephrine.

10. Epinephrine: Core Drug Knowledge • Pharmacotherapeutics • Wide variety of indications: asthma, shock, etc. • Pharmacokinetics • Administered: parenterally, topically, or by inhalation. Metabolism: liver. Absorption: into the tissues. Excreted: kidneys. Duration: 1-4 hours. • Pharmacodynamics • It stimulates all adrenergic receptors and causes adverse effects in the cardiovascular system and CNS.

11. Epinephrine: Core Drug Knowledge • Contraindications and precautions • Absolute contraindications to epinephrine include hypersensitivity, sulfite sensitivity, closed-angle glaucoma, and its use during labor. • Adverse effects • Severe adverse effects include hypertensive crisis, angina, cerebral hemorrhage, and cardiac arrhythmias. • Drug interactions • Tricyclic antidepressants, oxytocics, halogenated anesthetics, and beta blockers

12. Epinephrine: Core Patient Variables • Health status • Document preadministration vital signs. Review health history. • Life span and gender • Pregnancy risk category C • Lifestyle, diet, and habits • Document the patient’s occupation and daily activities. • Environment • IV administration only by trained personnel

13. Epinephrine: Nursing Diagnoses and Outcomes • Imbalanced Nutrition: Less Than Body Requirements related to drug-induced anorexia or nausea • Desired outcome: the patient will maintain adequate nutrition. • Disturbed Sleep Pattern, Insomnia, related to CNS excitation • Desired outcome: the patient will learn about and practice sleep hygiene. • Disturbed Sensory Perception related to impaired vision • Desired outcome: the patient will notify the provider if vision changes occur. • Ineffective Tissue Perfusion (Cardiopulmonary) related to cardiovascular effects of epinephrine • Desired outcome: the patient will notify the provider if tachycardia, chest pain, or palpitations occur.

14. Epinephrine: Planning & Interventions • Maximizing therapeutic effects • Requires close monitoring of vital signs and careful monitoring for adverse effects. • Take as prescribed. • Minimizing adverse effects • When treating anaphylactic shock, monitor blood pressure. • Assisting the patient with menu planning may help to promote appetite and counteract the anorectic influence of epinephrine.

15. Epinephrine: Teaching, Assessment & Evaluations • Patient and family education • Acute illness: Teaching should be brief, simple, and supportive. • Explain how to administer drug properly. • Ongoing assessment and evaluation • Assess the patient for resolution of the presenting problem. • Important to remember that epinephrine is a nonselective adrenergic agonist.

16. Question • Which of the following receptors is (are) stimulated by epinephrine? • A. Alpha 1 • B. Alpha 2 • C. Beta 1 • D. Beta 2 • E. All of the above

17. Answer • Which of the following receptors is (are) stimulated by epinephrine? • E. All of the above • Epinephrine is a nonselective adrenergic agonist. This drug stimulates alpha-1, alpha-2, beta-1, and beta-2 receptors. The only adrenergic receptor subtype it does not stimulate is the dopamine receptor.

18. Alpha-1 Adrenergic Agonists • The alpha-1 adrenergic agonists are drugs that stimulate the alpha-1 receptor directly. • Prototype drug: phenylephrine (Allerest)

19. Phenylephrine: Core Drug Knowledge • Pharmacotherapeutics • Used parenterally for vascular failure in shock. • Used topically for relief of nasal mucosal congestion. • Pharmacokinetics • Administered: parenterally or topically. Metabolism: liver. Excreted: urine. Onset: 15 to 20 minutes. Duration: 1-2 hours. • Pharmacodynamics • Is structurally similar to epinephrine and is a powerful alpha-1 adrenergic agonist.

20. Phenylephrine: Core Drug Knowledge • Contraindications and precautions • Hypersensitivity, sulfite sensitivity, severe hypertension, ventricular tachycardia, and closed-angle glaucoma • Adverse effects • Headache, restlessness, excitability, and reflex bradycardia • Drug interactions • Monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants, and oxytocics

21. Phenylephrine: Core Patient Variables • Health status • Assess medical history and obtain baseline assessment • Life span and gender • Used in pregnancy only if absolutely necessary • Lifestyle, diet, and habits • Document the patient’s occupation and activities of daily living • Environment • Closely monitor during administration in acute care setting

22. Phenylephrine : Nursing Diagnoses and Outcomes • Impaired Gas Exchange related to bronchoconstriction • Desired outcome: gas exchange will remain unimpaired. • Imbalanced Nutrition: Less Than Body Requirements related to anorexia or nausea • Desired outcome: the patient will take sufficient nourishment. • Disturbed Sleep Pattern, Insomnia, related to CNS excitation secondary to phenylephrine use • Desired outcome: the patient will maintain normal sleep patterns.

23. Phenylephrine: Planning & Interventions • Maximizing therapeutic effects • Corrected any blood losses prior to administration. • To produce optimal mydriasis, instill the ophthalmic form into the conjunctival cul-de-sac. • Minimizing adverse effects • IV administration is through a large vein. • Avoid driving at night because blurred vision can be hazardous.

24. Phenylephrine : Teaching, Assessment & Evaluations • Patient and family education • Stress the hazards associated with driving and operating heavy machinery. • Teach the patient about drug interactions. • Ongoing assessment and evaluation • Completing a detailed and thorough history and physical examination is essential for any patient anticipating long-term adrenergic drug therapy.

25. Alpha-2 & Beta-Adrenergic Agonists • Alpha-2 adrenergic agonists • Stimulation of alpha-2 receptors in the CNS decreases sympathetic outflow by inhibiting the release of norepinephrine. • Beta-adrenergic agonists • Beta-adrenergic agonists also mimic the action of the SNS. • Beta-adrenergic agonists are also labeled according to their selectivity. • Prototype: dopamine (Intropin).

26. Dopamine: Core Drug Knowledge • Pharmacotherapeutics • Used to correct the hemodynamic imbalances present in shock. • Pharmacokinetics • Distribution: throughout the tissues. Metabolism: kidney, liver, and plasma. Excreted: kidneys. Onset: 5 minutes. Duration: 10 minutes. • Pharmacodynamics • Stimulates alpha-1 and beta-1 receptors: increased cardiac output

27. Dopamine: Core Drug Knowledge • Contraindications and precautions • Pheochromocytoma, uncorrected tachyarrhythmias, and ventricular fibrillation • Adverse effects • Ectopic beats, nausea and vomiting, tachycardia, angina, palpitation, dyspnea, headache, hypotension, and vasoconstriction

28. Dopamine: Drug Interactions

29. Dopamine: Core Patient Variables • Health status • Assess medical history (chronic illness & allergies) • Life span and gender • Pregnancy category C drug • Environment • Administered only in acute care settings

30. Dopamine : Nursing Diagnoses and Outcomes • Risk for Ineffective Tissue Perfusion to Vital Organs related to drug effect • Desired outcome: the patient will maintain sufficient perfusion of vital organs to prevent serious damage. • Risk for Injury related to adverse effects of drug therapy • Desired outcome: adverse effects of drug therapy will not occur or will be minimized to prevent injury.

31. Dopamine: Planning & Interventions • Maximizing therapeutic effects • Administer using an infusion pump to regulate flow. • Titrate dose to desired effect. • Minimizing adverse effects • Follow the manufacturer’s instructions for dilution. • Monitor IV site. • Assess for disproportionate rise in diastolic blood pressure.

32. Dopamine: Teaching, Assessment & Evaluations • Patient and family education • If administered during a crisis, limited teaching occurs at that time. • Reassure the patient and family that the patient will be monitored closely during administration of the drug. • Ongoing assessment and evaluation • Treatment is effective if blood pressure stabilizes, urinary output returns to normal, and cardiac output returns to normal.

33. Question • Dopamine is administered by which route? • A. Oral • B. IM • C. IV • D. ET

34. Answer • Dopamine is administered by which route? • C. IV • Dopamine is given only via the IV route.

35. Dopaminergic Agonists • There are five types of dopamine receptors; only dopamine-1 (DA1) and dopamine-2 (DA2) receptors mediate responses in the adrenergic nervous system. • Stimulation of DA1 and DA2 receptors results in peripheral vasodilation. • Stimulating both receptors may have either complementary or opposing effects. • Prototype drug: fenoldopam (Corlopam)

36. Fenoldopam : Core Drug Knowledge • Pharmacotherapeutics • Short-term management of severe hypertension. • Pharmacokinetics • Administered: parenterally. Metabolism: by conjugation. Excreted: urine and feces. Steady state: 20 minutes. • Pharmacodynamics • It does not bind with DA2, alpha, or beta receptors. It provides rapid vasodilation to the coronary, renal, mesenteric, and peripheral arteries.

37. Fenoldopam : Core Drug Knowledge • Contraindications and precautions • Hypersensitivity to sulfites • Adverse effects • Symptomatic hypotension, tachycardia, abdominal or back pain, GI effects, sweating, and CNS effects, such as insomnia, dizziness, nervousness, or anxiety • Drug interactions • Beta blockers and diuretics

38. Fenoldopam : Core Patient Variables • Health status • Medical history and pre-administration physical assessment • Life span and gender • Pregnancy category B drug • Environment • Administered only in the acute care hospital setting

39. Fenoldopam : Nursing Diagnoses and Outcomes • Risk for Ineffective Tissue Perfusion related to hypotension, tachycardia, or increased intraocular pressure • Desired outcome: the patient will maintain adequate tissue perfusion throughout therapy. • Risk for Injury related to hypokalemia • Desired outcome: the patient will maintain a serum potassium level within normal limits throughout therapy.

40. Fenoldopam : Planning & Interventions • Maximizing therapeutic effects • Dilute with 0.9% sodium chloride or 5% dextrose. • The drug is administered using an infusion pump. • Titrate dose to effect. • Minimizing adverse effects • Visually inspect the drug ampule. • Start at low doses and titrate up to avoid reflex tachycardia. • Monitor vital signs during administration.

41. Fenoldopam : Teaching, Assessment & Evaluations • Patient and family education • Explain to the patient and family the rationale for the use. • Reassure the patient that close monitoring will be maintained throughout drug therapy. • Ongoing assessment and evaluation • Monitor vital signs throughout infusion. • Evaluate the efficacy by monitoring blood pressure.

42. Alpha-Adrenergic Antagonists • Alpha-adrenergic antagonists block the stimulation of alpha receptors. • Alpha-1a receptors mediate human prostatic smooth muscle contraction. • Alpha-1b and alpha-1d receptors are involved in vascular smooth muscle contraction. • Prototype drug: prazosin (Minipress).

43. Prazosin: Core Drug Knowledge • Pharmacotherapeutics • Used to treat congestive heart failure, Raynaud vasospasm, and prostatic outflow obstruction. • Pharmacokinetics • Administered: oral. Metabolism: liver. Excreted: bile, feces, and urine. Onset: 1 hour. Duration: 10 hours. • Pharmacodynamics • Blocks postsynaptic alpha-1 adrenergic receptors: lowers supine and standing blood pressure.

44. Prazosin: Core Drug Knowledge • Contraindications and precautions • Hypersensitivity; use caution with angina because hypotension may worsen the condition • Adverse effects • Light-headedness, dizziness, headache, drowsiness, weakness, lethargy, nausea, and palpitations • Drug interactions • Other antihypertensive medications

45. Prazosin: Core Patient Variables • Health status • Past medical history and physical assessment • Life span and gender • Pregnancy category C • Lifestyle, diet, and habits • Document the occupation and daily activities • Environment • Assess environment where drug will be given

46. Prazosin: Nursing Diagnoses and Outcomes • Ineffective Tissue Perfusion related to prazosin-induced hypotension • Desired outcome: the patient will maintain adequate tissue perfusion. • Imbalanced Nutrition: Less Than Body Requirements related to nausea secondary to prazosin use • Desired outcome: the patient will receive adequate nourishment by practicing appropriate dietary management. • Risk for Injury related to orthostatic hypotension • Desired outcome: the patient will remain free of injury.

47. Prazosin: Planning & Interventions • Maximizing therapeutic effects • Take as prescribed. • Refraining from OTC medication usage. • Minimizing adverse effects • Take the first dose just before bedtime. • Monitor weight and check for edema.

48. Prazosin: Teaching, Assessment & Evaluations • Patient and family education • Take drug as prescribed. • Adverse effects, including symptoms, to report to doctor. • Ongoing assessment and evaluation • Monitor blood pressure, heart and lung sounds, and edema. • Identify potential drug interactions.

49. Beta-Adrenergic Antagonists • Grouped according to their specificity of action at the beta-1 and beta-2 receptors. • Stimulation of beta-1 only (tachycardia, increased lipolysis, inotropy). • Stimulation of both beta-1 and beta-2 receptors (vasodilation, decreased peripheral resistance, bronchodilation). • Prototype drug: metoprolol (Lopressor, Toprol XL).

50. Metoprolol: Core Drug Knowledge • Pharmacotherapeutics • Treatment of hypertension, angina, and controlled congestive heart failure. • Pharmacokinetics • Administered: parenterally and orally. Metabolism: liver. Excreted: urine and breast milk. Onset & duration: varies with route of administration. • Pharmacodynamics • Decreased cardiac output and blood pressure. • Slowing of atrioventricular conduction and suppression of automaticity.