Pharmacology: Chapter 18 Adrenergic agonists

Drugs that stimulate the sympahetic nervous system are known as
Adrenergic agonists
Sympathomimetrics
Catecholamines
Substances that can produce a sympathomimetic response. They are either endogenous catecholamines (such as epinephrine, norepinephrine, and dopamine) or synthetic catecholamine drugs (such as dobutamine).
Adrenergic Receptors
-Located throughout the body
-Are receptors for the sympathetic neurotransmitters-Alpha-adrenergic, Beter-adrenergic, and dopaminergic receptors

Alpha 1 adrenergic receptors
Located on POSTsynaptic cells (the cell, muscle, or organ that the nerve stimulates)
Alpha 2 adrenergic receptors
Located on PREsynaptic nerve terminals (nerve that stimulates the effector cells) Controls the release of neurotransmitters
Alpha-adrenergic agonist responses
-Vasoconstriction
-CNS stimulation
Beta-Adrenergic Receptors
All are located on POSTsynaptic effector cells
Where are Beta 1 receptors normally found?
The heart
Where are Beta 2 receptors normally found?
Smooth muscle of the bronchioles, arterioles, and visceral organs
What’s the response of Beta-adrenergic drugs?

Bronchial, gastrointestinal, and uterine smooth muscle RELAXATION

Glycogenolysis

Cardiac STIMULATION

Dopaminergic receptors
Stimulated by dopamine
Response: dilation of renal, mesenteric, coronary, and cerebral blood vessels.
Direct-acting sympathomimetic
Binds directly to the receptor and causes a physiologic response
Indirect-acting sympathomimetic

Causes release of catecholamine from storage sites (vesicles) in nerve endings

catecholamine then binds to receptors and causes a physiologic response

Mixed-acting sympathomimetic
Directly stimulates the receptors by binding to it and indirectly stimulates the receptor by causing the release of stored neurotransmitters from vesicles in nerve endings
Drug effects of stimulation of alpha adrenergic receptors on smooth muscle results in

Vasoconstriction of blood vessels

Relaxation of GI smooth muscles (decreased
motility)

Constriction of bladder sphincter

Contraction of uterus

Male ejaculation

Contraction of pupillary muscles of the eye (dilated pupils)

Drug effects of stimulation of beta1 adrenergic receptors on the myocardium, atrioventricular node, and sinoatrial node results in

Increased force of contraction (positive inotropic effect)

Increased heart rate (positive chronotropic effect)

Increased conduction through AV node (positive dromotropic effect)

Drug effects of stimulation of beta2 adrenergic receptors on the airways results in
Bronchodilation
Uterine relaxation, glycogenolysis in liver, increased renin secretion in kidneys, relaxation of GI smooth muscle (decreased motility)

A patient has two inhalers that are due to be taken at the same time. One is a bronchodilator; the other is a corticosteroid. Which inhaler should the patient take first?

A. The bronchodilator
B. The corticosteroid
C. it does not matter which one is taken first.

A. The bronchodilator
Treatment of asthma and bronchitis

Bronchodilators that stimulate beta2 adrenergic receptors of bronchial smooth muscles causing relaxation resulting in bronchodilation

examples:
albuterol, ephedrine, epinephrine, formoterol, levarbuterol, metaproterenol, pirbuterol, salmeterol, and terbutaline

A patient is experiencing bronchospasms after running half a mile. He has several inhalers with him. Which one would be appropriate for treatment at this time?

A. albuterol
B. salmeterol
C. fluticasone
D. salmeterol and fluticasone combination (Advair Diskus)

A) albuterol

Rationale: Albuterol is a beta2 agonist that is used for acute bronchospasms

Treatment of nasal congestion
Alpha1 adrenergic receptors
intranasal (topical) application causes constriction of dilated arterioles and reduction of nasal blood flow, thus decreasing congestionexamples:
ephedrine, naphazoline, oxymetazoline, phenylephrine, and tetrahydrozoline

Temporary relief of conjunctival conjections

Alpha adrenergic receptors

Examples: epinephrine, naphazoline, phenylephrine, tetrahydrozoline

Vasoactive adrenergics

Also called cardioselective sympathomimetics

Used to support the heart during cardiac failure or shock; various alpha and beta receptors affected

Examples of vasoactive adrenergics
dobutamine dopamine
ephedrine epinephrine
fenoldopam phenylephrine
midodrine norepinephrine
Dobutamine (Dobutrex)
Beta1-selective vasoactive adrenergic drug that is structurally similar to the naturally occurring
catecholamine dopamineStimulates beta1 receptors on heart muscle (myocardium); increases cardiac output by increasing contractility (positive inotropy), which increases the stroke volume, especially in patients with heart failure.

Intravenous drug; given by continuous infusion

Dopamine (intropin)

Naturally occurring catecholamine neurotransmitter

Potent dopaminergic as well as beta1- and alpha1-adrenergic receptor activity

Low dosages: can dilate blood vessels in the brain, heart, kidneys, and mesentery, which increases blood flow to these areas (dopaminergic receptor activity).

Higher infusion rates: improve cardiac contractility and output (beta1-adrenergic receptor activity).
Highest doses: vasoconstriction (alpha1-adrenergic receptor activity).

Epinephrine (adrenalin)

Endogenous vasoactive catecholamine

Acts directly on both the alpha- and beta-adrenergic receptors of tissues innervated by the SNS

Prototypical nonselective adrenergic agonist

Administered in emergency situations
One of the primary vasoactive drugs used in many advanced cardiac life support protocols

Norepinephrine (levophea)

Stimulates alpha-adrenergic receptors

Causes vasoconstriction

Direct-stimulating beta-adrenergic effects on the heart (beta1-adrenergic receptors)

No stimulation to beta2-adrenergic receptors of the lung

Treatment of hypotension and shock

Administered by continuous infusion

Phenylephrine (Neo-synephrine)

Works almost exclusively on the alpha adrenergic receptors

used primarily for short term treatment to raise blood pressure in patients in shock

Control of supraventricular tachycardia

vasoconstriction in regional anesthesia

Topical opthalamic drug

Nasal decongestant

A patient on a dobutamine drip starts to complain that her intravenous line “hurts.” The nurse checks the insertion site and sees that the area is swollen and cool. What will the nurse do first?

A. Slow the intravenous infusion.
B. Stop the intravenous infusion.
C. Inject the area with phentolamine.
D. Notify the physician health care provider.

B) Stop the intravenous infusion

Rationale: Infiltration of an intravenous solution containing an adrenergic drug may lead to tissue necrosis from excessive vasoconstriction around the IV site.

What are the adverse effects for alpoha adrenergic drugs?
CNS
-Headache, restlessness, excitement, insomnia, euphoria
CARDIOVASCULAR
-Palpitations (dysrhythmias), tachycardia, vasoconstriction, hypertension
OTHER
-Loss of apeptite,dry mouth, nausea, vomiting, taste changes
What are the adverse effects for beta adrenergic drugs?
CNS
– MIld tremors, headaches, nervousness, dizziness
CARDIOVASCULAR
-Increased heart rate, palpitations (dysrhythmias), fluctuations in blood pressure
OTHER
-Sweating, nausea, vomiting, and muscle cramps
What are the interactions?
Anesthetic drugs, tricyclic antidepressants, MAOLs, antihistamines, thyroid preparations, adrenergic antagonists
Intravenous (IV) administration

Check IV site often for infiltration

use clear IV solutions

Use an infusion pump

Infuse drug slowly to avoid dangerous cardiovascular effects

monitor cardiac rhythm

True or False: Salmeterol is indicated for prevention of bronchospasms, not management of acute symptoms
TRUE
What can happen if you administer 2 adrenergic drugs together?
May precipitate severe cardiovascular effects such as tachycardia or hypertension

A patient on a dobutamine drip starts to complain that he feels a “tightness” in his chest that he had not felt before. What will the nurse do first?

A. Check the infusion site for possible extravasation.
B. Increase the infusion rate.
C. Check the patient’s vital signs.
D. Order an electrocardiogram.

C. Check the patient’s vital signs.

A 10-year-old child is brought to the emergency department while having an asthma attack. She is given a nebulizer treatment with albuterol. The nurse’s immediate assessment priority would be to

A. determine the time of the child’s last meal.
B. monitor Spo2 with a pulse oximeter.
C. monitor the child’s temperature.
D. provide education on asthma management.

B. monitor Spo2 with a pulse oximeter.

Rationale: During administration of albuterol, a fast-acting beta2 agonist, the nurse should monitor the patient’s respiratory status including SpO2 (with a pulse oximeter), respiratory rate, and breath sounds to ensure that the medication is having a therapeutic effect. The other items can be handled after her respiratory status is stable

direct-acting adrenergics have a greater effect on the peripheral nervous system, whereas indirect-acting adrenergics impact the central nervous system.
Which is true about the effect epinephrine has on cardiac output?
Epinephrine increases cardiac output by stimulating muscle contractions in the cardiovascular system.
Which condition is contraindicated for administration of albuterol?
Albuterol is contraindicated for patients taking MAOI therapy.
Which lab values should be documented with the administration of epinephrine?
Liver and Renal function
Epinephrine and albuterol are common sympathomimetic drugs. Epinephrine activates all four subtypes (alpha 1, alpha 2, beta 1, and beta 2) of adrenergic receptors. It is used for a variety of conditions, including anaphylaxis and cardiac arrest, and can be used for bleeding control.
Albuterol has selective action on beta 2 receptors and therefore is useful in the treatment of bronchospasm.
Which would be a casual contraindication to the use of adrenergic drugs?
When administering an alpha blocker for the first time , it is important for the nurse to assess the patient for the development of
Hypotenstion
Pheochromocytoma
A vascular adrenal gland tumor that is usually benign but secretes epinephrine and norepinephrine, this often causes CNS stimulation and substantial BP elevation
first dose phenomenon
Severe and sudden drop in BP after the administration of the first dose of an alpha adrenergic blocker

Drugs that effect the sympathetic nervous system are termed adrenergic agonists and adrenergic blockers Adrenergic agonists are also called sympathomimetics or adrenomimetics WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY TOPIC SPECIFICALLY FOR YOU FOR ONLY $13.90/PAGE Write my …

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