Adrenergic bronchodilators are a class of drugs used to treat bronchospasm and reversible airflow obstruction. They are often administered to patients with conditions such as asthma, emphysema, chronic bronchitis, and bronchiectasis.

In this article, we will provide an overview of adrenergic bronchodilators, including the different types, indications, and side effects.

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What are Adrenergic Bronchodilators?

Adrenergic bronchodilators are the most common aerosolized drugs that are administered in the field of respiratory care. They are used to treat bronchospasm and improve flow rates, thereby making it easier for the patient to breathe.

They work by stimulating alpha, beta-1, and beta-2 receptors. Alpha-receptor stimulation causes vasoconstriction, which could result in increased blood pressure.

B1-receptor stimulation causes an increased heart rate, which explains why tachycardia is one of the most common side effects of adrenergic agents.

B2-receptor stimulation cause relaxation of the bronchial smooth muscle tissue, which helps the airways open up so that air can flow more easily.

Side Effects

The most common side effects of adrenergic bronchodilators include the following:

  • Tachycardia
  • Shakiness
  • Tremors
  • Palpitations
  • Excessive sweating
  • Anxiety
  • Insomnia

Each patient reacts differently to adrenergic bronchodilators, and some may experience more side effects than others.

However, it’s important to monitor the patient’s heart rate closely while administering a beta-2 agonist. Tachycardia is the most common side effect and can occur even at therapeutic doses.

Therefore, adrenergic bronchodilators may be contraindicated in patients with cardiovascular conditions such as arrhythmias and hypertension.

Types of Adrenergic Bronchodilators

The types of adrenergic bronchodilators are classified according to the time of onset, which includes:

  1. Ultrashort-acting agents
  2. Short-acting agents
  3. Long-acting agents

There are several different types of drugs that fall into one of these three categories depending on how fast their effects take place.

Ultrashort-Acting Agents

Ultrashort-acting bronchodilators have the quickest onset, which occurs in 3-5 minutes.

The most common type is racemic epinephrine (Asthmanefrina), which is typically administered for its vasoconstriction effects.

Therefore, it can be used to treat upper airway swelling that occurs in patients with croup and epiglottitis. It can also be used to treat airway bleeding that occurs during an endoscopy.

Short-Acting Agents

Short-acting bronchodilators have an onset of 5-15 minutes and are the most common type of bronchodilator used for the treatment of asthma. Some examples include:

  • Albuterol (Proventil)
  • Levalbuterol (Xopenex)

Albuterol and levalbuterol are both beta-2 agonists that are used to treat bronchospasm. They are inhaled aerosol drugs that can be administered with a metered-dose inhaler (MDI) or small-volume nebulizer (SVN).

Long-Acting Agents

Long-acting bronchodilators have an onset of 20 minutes or more. They are typically used for the maintenance of bronchospasm and asthma symptoms. Therefore, they should not be administered during an acute exacerbation.

Some examples of long-acting bronchodilators include:

  • Salmeterol (Serevent Diskus)
  • Formoterol (Perforomist)
  • Arformoterol (Brovana)
  • Indacaterol (Arcapta Neohaler)
  • Olodaterol (Stiverdi Respimat)

Again, long-acting bronchodilators have a slower time to peak effect, which makes them ineffective during an acute exacerbation.

Adrenergic Bronchodilators Practice Questions:

1. What is an adrenergic bronchodilator?
It is an agent that stimulates sympathetic nervous fibers, which allows relaxation of smooth muscle in the airway. It is also known as a sympathomimetic bronchodilator or B2 agonist.

2. What happens during a-receptor stimulation?
It causes vasoconstriction and vasopressor effect; in the upper airway (nasal passages), this can provide decongestion.

3. What is the asthma paradox?
Refers to the increasing incidence of asthma morbidity, and especially asthma mortality, despite advances in the understanding of asthma and availability of improved drugs to treat asthma.

4. What happens during B1-receptor stimulation?
Causes increased myocardial conductivity, heart rate, and contract force.

5. What happens during B2-receptor stimulation?
Causes relaxation of bronchial smooth muscle, with some inhibition of inflammatory mediator release and stimulation of mucociliary clearance.

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6. What is bronchospasm?
Narrowing of the bronchial airways caused by contraction of smooth muscles.

7. What are catecholamines?
Group of similar compounds having sympathomimetic action and they mimic the actions of epinephrine causing increase HR, smooth muscle relaxation of bronchioles and skeletal muscle blood vessels. It is used for tachycardia, elevated BP, smooth muscle relaxation, glycogenolysis, skeletal muscle tremor and CNS stimulation. Duration is 1.5 to 3 hours and inactivated by gut/liver, heat, air and light.

8. What is cyclic adenosine 3′ and 5′-monophosphate cAMP?
Nucleotide produced by B2-receptor stimulation. It affects many cells, but causes relaxation of bronchial smooth muscle.

9. What is a sympathomimetic?
It produces effects similar to those of the sympathetic nervous system.

10. What is a short-acting B2 agonist?
Albuterol, levalbuterol, or metaproterenol are indicated for relief of acute reversible airflow obstruction in asthma or other obstructive airway diseases like COPD.

11. What diseases are treated with long-acting agents such as salmeterol, formoterol, arformoterol, indacaterol, and olodaterol?
The maintenance of bronchodilation and control of bronchospasm and nocturnal symptoms in asthma or other obstructive diseases like COPD.

12. What is racemic epinephrine?
Used as in inhaled aerosol or by direct lung instillation and control airway bleeding during endoscopy to reduce airway swelling. It is used for the strong a-adrenergic vasoconstriction effect and for reducing airway swelling after extubation. It is also done during epiglottitis, croup, or bronchiolitis and to control airway bleeding during endoscopy.

13. What is the duration of racemic epinephrine?
It is an ultra-short acting drug (duration less than 3 hours).

14. What types of drugs are albuterol, levalbuterol, and metaproterenol?
Short-acting (duration 4 to 6 hours).

15. What types of drugs are salmeterol, formoterol, arformoterol, indacatferol, olodaterol?
Long-acting (duration 12 to 24 hours).

16. What should be done by the respiratory therapist before a treatment?
Assess the effectiveness of drug therapy b, monitor flow rates, perform a respiratory assessment, and assess pulse.

17. What should be done by the respiratory therapist during a treatment?
Assess patient subjective reaction, assess arterial blood gases sat, and note the effect of B agonists.

18. What is a benefit of Xopenex?
Does not affect heart rate.

19. What is Brovana?
It is a long-acting inhalation solution given for COPD and has to be refrigerated. Arformoterol (nebulizer solution), duration: up to 12 hours, use: maintenance treatment of COPD and asthma not controlled by corticosteroids.

20. What is the FiO2 of room air?
21%.

21. What is Micronefrin?
The brand name of Racemic Epinephrine

22. What is the dose of Racemic Epinephrine?
0.5ml of 2.25%/2.5ml NS.

23. What kind of adrenergic bronchodilator is racemic and epinephrine?
Ultra-short-acting (acute therapy).

24. What are the brand names of albuterol?
Accuneb, Ventolin, Proventil, ProAir, and Vospire.

25. What are the modes of delivery for albuterol?
SVN, MDI, and tablet.

26. What is the dose for SVN albuterol?
0.5ml of 0.5%/2.5ml NS.

27. What is the dose for MDI albuterol?
90 ug/puff.

28. What is the brand name of levalbuterol?
Xopenex.

29. What are the modes of delivery for levalbuterol?
SVN and MDI.

30. What is the dose for SVN levalbuterol?
0.63mg/3ml NS and 1.25mg/3ml NS.

31. What is the dose for MDI levalbuterol?
45ug/puff.

32. What kind of adrenergic bronchodilator are levalbuterol and albuterol?
Short-acting (acute therapy).

33. What is the mode of delivery for arformoterol?
SVN

34. What is the SVN dose for arformoterol?
15 ug/2ml NS

35. What are the brand names for formoterol?
Perforomist and foradil.

36. What are the modes of delivery for formoterol?
SVN and DPI.

37. What is the SVN dose for formoterol?
20 ug/2ml NS.

38. What is the DPI dose for formoterol?
12 ug/inhalation.

39. What is the Brand name for salmeterol?
Serevent.

40. What is the mode of delivery for salmeterol?
DPI.

41. What is the DPI dose of salmeterol?
50 ug/inhalation.

42. What type of adrenergic bronchodilator are arformoterol, formoterol, and salmeterol?
Long-acting (Maintenance Therapy).

43. What are the indications for adrenergic bronchodilators?
Asthma, bronchitis, emphysema, bronchiectasis, and obstructive airway diseases.

44. What are the indications for short-acting agents?
Acute reversible airflow obstruction.

45. What are examples of short-acting agents?
Albuterol, levalbuterol, and metaproterenol.

46. What are the indications for long-acting agents?
Maintenance bronchodilation, control bronchospasm, and control nocturnal symptoms.

47. What are examples of long-acting agents?
Salmeterol, formoterol, arformoterol, indacaterol, and olodaterol.

48. What is used to treat postextubation strider?
Racemic epinephrine.

49. What is used to treat epiglottitis, croup, and bronchiolitis?
Racemic epinephrine.

50. What is an ultra-short acting drug?
Duration <3 hours. Example is racemic epinephrine.

51. What is a short-acting drug?
Duration 4 to 6 hours. Examples are albuterol, levalbuterol, and metaproterenol.

52. What is a long-acting drug?
Duration 12 to 24 hours. Examples are salmeterol, formoterol, arformoterol, indacaterol, and olodarerol.

53. What is epinephrine?
Potent catecholamine bronchodilator and stimulates alpha and beta receptors. It helps in vasoconstriction of peripheral blood vessels.

54. What are the side effects of epinephrine?
Tachycardia, elevated blood pressure, tremor, headaches, and insomnia.

55. What is a characteristic of contact B-adrenergic agents?
They offer less frequent dosing and nocturnal protection.

56. What is performist/foradil?
B2-selective agonist (SVN and DPI), short peak effect 3 minutes, duration of up to 12 hours and used for: asthma, exercise induced bronchospasm (both 5yrs or older), and COPD.

57. What are the safety concerns of long-acting B2 agonists?
Not to be used with a controller medicine, only by patients on low dose or medium dose ICS and should only be used short term and if patients are not controlled by ICS.

58. What does an a-receptor do?
Vasoconstriction effect.

59. What does a B1-receptor do?
Increase HR and contractile force.

60. What does a B2-receptor do?
Relaxation of bronchial smooth muscle.

61. What is the purpose of continuous nebulization of albuterol?
Management of asthma reduces the need for frequent therapist attendance and dose: 10-15 mg/hour.

62. What are the complications of continuous nebulization of albuterol?
Cardiac arrhythmias, hypokalemia, hyperglycemia, and tremor.

63. What is good about oral delivery?
Easy to use/short admin time/reproducibility and controlled dosage. The longer onset of action, systematic side effects, and loss due to the first pass of the liver.

64. What are the side effects of albuterol?
Tremor, cardiac effects, tolerance to bronchodilator effect, loss of Broncho protection, CNS effects, fall in PaO2, metabolic disturbances, propellant toxicity, and sensitivity to additives

65. What are the two types of ultrashort-acting drugs involved with adrenergic bronchodilators?
Epinephrine and racemic epinephrine.

66. What are the trade names for epinephrine?
Primatene mist, adrenalin chloride, asthmahaler and medihaler-epi.

67. What is the onset, peak, and duration of epinephrine?
Onset: 3-5 mins; Peak: 5-20 mins; and, duration: 1-3 hours.

68. What are the trade names of racemic epinephrine?
Micronephrine, nephron and asthmanefrin.

69. What is the onset, peak, and duration of racemic epinephrine?
Onset: 3-5 mins; Peak: 5-20 mins; and, duration: .5-2 hours.

70. What are the dosages needed when prescribing racemic epinephrine (solutions, mL, and mg)?
2.25% solution, .025-0.5 mL and 5.63-11.25 mg, QID.

71. What are the seven short-acting drugs associated with adrenergic bronchodilators?
Albuterol sulfate, pirbuterol, levalbuterol, isoproterenol, terbutaline, isoetharine and bitolterol.

72. What are the two trade names associated with metaproterenol?
Alupent and metraprel.

73. What are the trade names associated with albuterol sulfate?
Ventolin, Ventolin HFA, Proventil HFA, Proventil, volmax, ProAir HFA, Vospire ER, AccuNeb and Airet.

74. What are the dosages needed when distributing albuterol sulfate?
SNV: 0.5% solution; 2.5 mg QID; (10 mg for K+tx) and MDI: 90 micrograms/puff QID.

75. What are the onset, duration, and peak of albuterol sulfate?
Onset: 15 mins; peak: 30-60 mins; and, duration: 5-8 hours.

76. What are the two trade names associated with pirbuterol?
Maxair and maxair autohaler.

77. What are the two trade names associated with levabuterol?
Xopenex HFA and Xopenex.

78. What is the dosage amount of Xopenex HFA?
MDI: 45 micrograms/puffs and TID/QID.

79. What are the onset, peak, and duration of Xopenex HFA?
Onset: 15 minutes; Peak: 30-60 minutes; and, duration: 5-8 hours.

80. What is the dosage amount of Xopenex?
Adult: 1.25 mg; Ped: 0.63 mg; and, TID.

81. What are the three trade names associated with isoproterenol?
Isuprel, isuprel mistometer, and medihaler-iso.

82. What are the two trade names associated with isoetharine?
Bronkometer and bronkosol.

83. What is the trade name associated with bitolterol?
Tornalate.

84. What are the three long-acting drugs associated with adrenergic bronchodilators?
Salmeterol, formoterol, and arformoterol.

85. What is the trade name associated with salmeterol?
Serevent diskus.

86. What is the dosage amount of salmeterol?
DPI: 50 micrograms BID.

87. What are the onset, peak, and duration of salmeterol/Serevent Diskus?
Onset: 20 mins; peak: 3-5 hours; and, duration: 12 hours.

88. What are the trade names associated with arformoterol?
Brovana and fortadil certihaler.

89. Where are alpha-adrenergic receptors usually found when they are stimulated by epinephrine or non-epinephrine?
The smooth muscle membranes.

90. Where are beta-adrenergic receptors found?
On cardiac muscles and some smooth muscle.

91. What does Beta 1 – (cardiac muscles) do when stimulated by epinephrine or norepinephrine?
They increase the heart rate and strength of contraction.

92. What causes Beta 2- (smooth muscle in the lungs) when stimulated by epinephrine?
Vasodilatation of certain vessels and bronchodilation of the bronchial smooth muscles.

93. What are the two main types of classifications that affect the sympathetic system?
Sympathomimetic and sympatholytic.

94. What do sympathomimetics do to the body?
Increase BP, increase HR and Broncho dilate.

95. How do drugs, including epinephrine and norepinephrine, produce contractions of the smooth muscle?
They do so by stimulating the alpha receptors.

96. What happens when using drugs containing epinephrine stimulate both the alpha and the beta receptors?
Relaxation of the bronchial smooth muscle Beta 2 along with the alpha stimulation effects and the Beta.

97. What do sympatholytic drugs do?
They block the sympathothetic system, decrease in BP, and decrease in HR. They are used for: hypertension, angina, and certain cardiac arrhythmias.

98. What is the function of alpha receptors?
Generally excite, with the exception of the intestine and CNS receptors, where inhibition or relaxation occur.

99. Where are alpha sympathetic receptors found?
On peripheral blood vessels.

100. What does the stimulation of alpha sympathetic receptors cause?
Vasoconstriction.

101. What is the function of beta receptors?
Generally inhibit or relax, with the exception of the heart where stimulation occurs.

102. Where is beta 1 receptors located?
The heart as it increases the rate and contractile force.

103. Where is beta 2 receptors located?
The lungs; bronchial, vascular, and smooth muscle. It relaxes bronchial smooth muscle and vascular beds of skeletal muscle.

104. How does the sympathetic nervous system control bronchial smooth muscle tone?
By circulating epinephrine and norepinephrine.

105. What does epinephrine stimulate?
Alpha and beta receptors.

106. What does norepinephrine stimulate?
Primarily alpha receptors.

107. What do parasympathetic vagal nerves innervate?
The lungs.

108. What do vagus nerves in the lungs release?
ACh.

109. What are short-acting beta 2 agonists (levalbuterol, albuterol) indicated for?
Relief of acute reversible airflow obstruction, rescue agents or relievers, COPD and asthma.

110. What are indications for long-acting agents (salmeterol)?
Maintenance of bronchodilation, control of bronchospasm, nocturnal symptoms and controllers.

111. When is racemic epinephrine used?
To reduce airway swelling after: extubation, epiglottitis, croup, bronchiolitis, and control airway bleeding during endoscopy.

112. How long do ultrashort-acting bronchodilators last?
Less than 3 hours. These are epinephrine and racemic epinephrine.

113. How long do short-acting bronchodilators last?
4-6 hours. These are albuterol, levalbuterol, metaproterenol, and pirbuterol.

114. How long do long-acting bronchodilators last?
12 hours: Salmeterol.

115. What does epinephrine stimulate?
Alpha and beta receptors.

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116. Where is epinephrine stored?
Adrenal medulla.

117. What is the onset of epinephrine?
Rapid.

118. What is the duration of epinephrine?
Short.

119. What is epinephrine typically used for?
Acute asthma, post-extubation, and airway edema.

120. What are examples of catecholamines?
Epinephrine, Isoproterenol, Isoetharine and Bitolterol.

121. What are examples of non-catecholamines?
Metaproterenol, Terbutaline, Albuterol, Pirbuterol and Salmeterol.

122. How will patients sputum appear after using aerosols of catecholamines?
Pink-tinged.

123. What are resorcinol and saligenin?
Increased duration of action (up to 6 hours), may be taken orally and minimal beta 1 side effects.

124. What are the adverse side effects of adrenergic bronchodilators?
Tremor, palpitations, tachycardia, headache, insomnia, increased BP, nervousness, nausea, tolerance, decreased PaO2 as O2 is going to airways that are not open yet, hypokalemia and propellant induced bronchospasm.

125. What are tremors caused by?
They are caused by the stimulation of beta-2 receptors in skeletal muscle.

Final Thoughts

Adrenergic bronchodilators are a class of drugs used to treat bronchospasm in patients with asthma and COPD. They work by stimulating alpha, beta-1, and beta-2 receptors.

The most common side effects include tachycardia, shakiness, and tremors. Tachycardia is the most common side effect, which should be a major consideration in patients with cardiovascular conditions.

There are three types of adrenergic bronchodilators classified according to the time of onset, which include ultrashort-acting, short-acting, and long-acting agents.

We have a similar guide on anticholinergic bronchodilators that I think you’ll find helpful. Thanks for reading, and, as always, breathe easy, my friend.

Medical Disclaimer: This content is for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Please consult with a physician with any questions that you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you read in this article. We strive for 100% accuracy, but errors may occur, and medications, protocols, and treatment methods may change over time.

References

The following are the sources that were used while doing research for this article:

  • Faarc, Gardenhire Douglas EdD Rrt-Nps. Rau’s Respiratory Care Pharmacology. 10th ed., Mosby, 2019.
  • Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
  • Reed, C. “Adrenergic Bronchodilators: Pharmacology and Toxicology.” PubMed, Aug. 1985, pubmed.ncbi.nlm.nih.gov/2862174.
  • “Beta 2 Agonists – StatPearls – NCBI Bookshelf.” StatPearls, ncbi.nlm.nih.gov/books/NBK542249.

Medical Disclaimer: The information provided by Respiratory Therapy Zone is for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Please consult with a physician with any questions that you may have regarding a medical condition.