Adrenergic Bronchodilators: Overview and Practice Questions

Adrenergic bronchodilators are essential medications used to manage respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other breathing disorders.

These drugs work by stimulating beta-adrenergic receptors in the lungs, helping to relax and widen the airways. As a result, they relieve common respiratory symptoms like wheezing, shortness of breath, and chest tightness.

This article explores the mechanisms, types, and clinical uses of adrenergic bronchodilators to provide a comprehensive overview of these life-saving medications.

What are Adrenergic Bronchodilators?

Adrenergic bronchodilators are medications that relax the muscles around the airways, helping to open them and improve airflow. They work by stimulating beta-adrenergic receptors in the lungs, primarily beta-2 receptors, which trigger the relaxation of bronchial smooth muscles.

These drugs are commonly used to treat respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other obstructive airway disorders.

Adrenergic bronchodilators are classified into short-acting (SABAs) like albuterol, providing quick relief during asthma attacks, and long-acting (LABAs) like salmeterol, used for long-term management. They reduce symptoms such as wheezing, shortness of breath, and chest tightness, enhancing overall breathing efficiency.

Side Effects

While adrenergic bronchodilators are highly effective in managing respiratory conditions, they can cause side effects, especially with prolonged or excessive use.

Common side effects include:

• Tremors: Shaking or trembling of the hands due to stimulation of beta receptors in muscles.
• Increased Heart Rate (Tachycardia): These medications can cause a rapid heartbeat or palpitations.
• Nervousness or Anxiety: Some users may experience restlessness or anxiety.
• Headache: Mild to moderate headaches can occur after use.
• Dizziness: This may result from changes in blood pressure or heart rate.
• Muscle Cramps: Electrolyte imbalances can cause occasional cramping.
• Dry Mouth or Throat Irritation: Inhaler use may cause dryness or irritation in the mouth and throat.
• Chest Pain (Angina): May occur due to increased heart workload.
• High Blood Pressure: Can develop in sensitive individuals.
• Severe Allergic Reactions: Though uncommon, symptoms like rash, swelling, or difficulty breathing require immediate medical attention.

Note: Proper use and monitoring by healthcare providers help minimize side effects, ensuring safe and effective treatment.

Types of Adrenergic Bronchodilators

Adrenergic bronchodilators are classified into three main categories based on their onset of action and duration of effect. These categories are:

1. Ultrashort-Acting Agents
2. Short-Acting Agents (SABAs)
3. Long-Acting Agents (LABAs)

Each type serves specific therapeutic purposes, depending on how quickly and how long their effects last. Watch this video and keep reading to learn more about each specific type of adrenergic bronchodilator.

Ultrashort-Acting Agents

Ultrashort-acting bronchodilators provide the fastest relief, with an onset of action within 3-5 minutes. Their effects are brief, making them useful in emergency situations or specific clinical settings.

Common Example:

• Racemic Epinephrine (Asthmanefrin): This medication works by stimulating both alpha and beta receptors, causing both bronchodilation and vasoconstriction. It is often administered via nebulization.

Clinical Uses:

• Upper Airway Swelling: Treats swelling caused by croup or epiglottitis.
• Airway Bleeding: Helps manage airway bleeding during procedures like bronchoscopy or endoscopy.

Short-Acting Agents (SABAs)

Short-acting bronchodilators, commonly referred to as SABAs, have an onset of action within 5-15 minutes and are considered rescue medications. Their effects last 4-6 hours, making them ideal for relieving acute asthma symptoms or other bronchospastic conditions.

Common Examples:

• Albuterol (Proventil, Ventolin): A widely used beta-2 agonist that relaxes bronchial smooth muscles.
• Levalbuterol (Xopenex): A more selective form of albuterol with potentially fewer side effects.

Administration Methods:

• Metered-Dose Inhaler (MDI): Common for home and emergency use.
• Small-Volume Nebulizer (SVN): Often used in hospital settings for more severe cases.

Clinical Uses:

• Asthma Attacks: Provides rapid relief from wheezing, shortness of breath, and chest tightness.
• Exercise-Induced Bronchospasm: Taken before physical activity to prevent symptoms.

Long-Acting Agents (LABAs)

Long-acting bronchodilators have a delayed onset of at least 20 minutes, with effects lasting 12-24 hours. They are used as maintenance medications for chronic respiratory conditions and should not be used for acute symptom relief.

Common Examples:

• Salmeterol (Serevent Diskus): Commonly prescribed for asthma and COPD.
• Formoterol (Perforomist): Provides long-term bronchodilation for COPD management.
• Arformoterol (Brovana): A nebulized form for long-term COPD management.
• Indacaterol (Arcapta Neohaler): Approved for once-daily use in COPD.
• Olodaterol (Striverdi Respimat): A long-acting inhaler used for COPD maintenance.

Clinical Uses:

• Maintenance Therapy: Controls chronic asthma and COPD symptoms.
• Combination Therapies: Often prescribed with inhaled corticosteroids for added anti-inflammatory effects.

Note: LABAs are not rescue inhalers and should never be used during an acute asthma or COPD exacerbation. Their slower onset makes them ineffective for sudden breathing difficulties.

Adrenergic Bronchodilator Practice Questions

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

2. What happens during α-receptor stimulation?
α-Receptor stimulation causes vasoconstriction and a vasopressor effect. In the upper airway (nasal passages), this leads to decongestion.

3. What is the asthma paradox?
The asthma paradox refers to the increasing incidence of asthma-related morbidity and mortality despite advances in asthma management and the availability of effective drugs.

4. What happens during B1-receptor stimulation?
B1-receptor stimulation increases myocardial conductivity, heart rate, and the force of heart muscle contractions.

5. What happens during B2-receptor stimulation?
B2-receptor stimulation relaxes bronchial smooth muscle, inhibits the release of inflammatory mediators, and stimulates mucociliary clearance.

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

7. What are catecholamines?
Catecholamines are compounds with sympathomimetic effects that mimic epinephrine. They increase heart rate, relax bronchial smooth muscle, and dilate skeletal muscle blood vessels. They are used to manage tachycardia, elevated BP, smooth muscle relaxation, and CNS stimulation. Their duration is 1.5 to 3 hours, and they are inactivated by the gut, liver, heat, air, and light.

8. What is cyclic adenosine 3′ and 5′-monophosphate (cAMP)?
cAMP is a nucleotide produced during B2-receptor stimulation that relaxes bronchial smooth muscle and regulates various cellular functions.

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

10. What is a short-acting B2 agonist?
Short-acting B2 agonists like albuterol, levalbuterol, and metaproterenol provide quick relief from acute reversible airflow obstruction in asthma and COPD.

11. What diseases are treated with long-acting agents like salmeterol, formoterol, arformoterol, indacaterol, and olodaterol?
These agents are used for the maintenance of bronchodilation and the management of asthma, COPD, and nocturnal symptoms.

12. What is racemic epinephrine?
Racemic epinephrine is used as an inhaled aerosol or by direct lung instillation to reduce airway swelling, control bleeding during endoscopy, and manage conditions like epiglottitis, croup, and bronchiolitis.

13. What is the duration of racemic epinephrine?
Racemic epinephrine is an ultra-short-acting drug with a duration of less than 3 hours.

14. What types of drugs are albuterol, levalbuterol, and metaproterenol?
These are short-acting B2 agonists with a duration of 4 to 6 hours.

15. What types of drugs are salmeterol, formoterol, arformoterol, indacaterol, and olodaterol?
These are long-acting B2 agonists with durations of 12 to 24 hours.

16. What should be done by the respiratory therapist before a treatment?
The therapist should assess the effectiveness of drug therapy, monitor flow rates, perform a respiratory assessment, and check the patient’s pulse.

17. What should be done by the respiratory therapist during a treatment?
The therapist should monitor the patient’s subjective reaction, check arterial blood gas levels, and observe the effects of B-agonists.

18. What is a benefit of Xopenex?
Xopenex (levalbuterol) provides bronchodilation without significantly affecting heart rate.

19. What is Brovana?
Brovana (arformoterol) is a long-acting inhalation solution used for the maintenance treatment of COPD. It must be refrigerated and has a duration of up to 12 hours.

20. What is the FiO2 of room air?
The FiO2 (fraction of inspired oxygen) of room air is 21%.

21. What is Micronefrin?
Micronefrin is the brand name of racemic epinephrine.

22. What is the dose of racemic epinephrine?
The dose is 0.5 mL of 2.25% racemic epinephrine mixed with 2.5 mL of normal saline (NS).

23. What kind of adrenergic bronchodilator is racemic epinephrine?
Racemic epinephrine is an ultra-short-acting bronchodilator used for acute therapy.

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

25. What are the modes of delivery for albuterol?
Albuterol can be administered via SVN (small-volume nebulizer), MDI (metered-dose inhaler), and tablet.

26. What is the dose for SVN albuterol?
The standard dose is 0.5 mL of 0.5% albuterol mixed with 2.5 mL of normal saline (NS).

27. What is the dose for MDI albuterol?
The dose for MDI albuterol is 90 mcg per puff.

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

29. What are the modes of delivery for levalbuterol?
Levalbuterol can be delivered via SVN and MDI.

30. What is the dose for SVN levalbuterol?
The standard doses are 0.63 mg/3 mL NS and 1.25 mg/3 mL NS.

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

32. What kind of adrenergic bronchodilators are levalbuterol and albuterol?
They are short-acting bronchodilators used for acute therapy.

33. What is the mode of delivery for arformoterol?
SVN (Small Volume Nebulizer)

34. What is the SVN dose for arformoterol?
15 mcg/2 mL NS

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

36. What are the modes of delivery for formoterol?
SVN and DPI (Dry Powder Inhaler).

37. What is the SVN dose for formoterol?
20 mcg/2 mL NS

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

39. What is the brand name for salmeterol?
Serevent

40. What is the mode of delivery for salmeterol?
DPI (Dry Powder Inhaler)

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

42. What type of adrenergic bronchodilators are arformoterol, formoterol, and salmeterol?
They are long-acting bronchodilators used for maintenance therapy.

43. What are the indications for adrenergic bronchodilators?
Treatment of asthma, bronchitis, emphysema, bronchiectasis, and other obstructive airway diseases.

44. What are the indications for short-acting agents?
Relief of 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 of bronchospasm, and management of nocturnal symptoms.

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

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

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

50. What is an ultra-short acting drug?
An ultra-short-acting drug has a duration of less than 3 hours. An example is racemic epinephrine.

51. What is a short-acting drug?
A short-acting drug has a duration of 4 to 6 hours. Examples include albuterol, levalbuterol, and metaproterenol.

52. What is a long-acting drug?
A long-acting drug has a duration of 12 to 24 hours. Examples include salmeterol, formoterol, arformoterol, indacaterol, and olodaterol.

53. What is epinephrine?
Epinephrine is a potent catecholamine bronchodilator that stimulates alpha and beta receptors, causing vasoconstriction of peripheral blood vessels and bronchodilation.

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

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

56. What is Perforomist/Foradil?
Perforomist/Foradil is a B2-selective agonist available as SVN and DPI. It has a short peak effect of 3 minutes, a duration of up to 12 hours, and is used to treat asthma, exercise-induced bronchospasm (for ages 5 and older), and COPD.

57. What are the safety concerns of long-acting B2 agonists?
Long-acting B2 agonists should not be used without a controller medication. They should be prescribed only to patients already on low- or medium-dose inhaled corticosteroids (ICS) and used for short-term symptom management.

58. What does an α-receptor do?
It causes vasoconstriction, leading to reduced swelling and increased blood pressure.

59. What does a B1-receptor do?
It increases heart rate and contractile force of the heart.

60. What does a B2-receptor do?
It causes relaxation of bronchial smooth muscle, resulting in bronchodilation.

61. What is the purpose of continuous nebulization of albuterol?
Continuous nebulization of albuterol is used to manage severe asthma, reducing the need for frequent therapist intervention. The typical dose is 10-15 mg/hour.

62. What are the complications of continuous nebulization of albuterol?
Complications include cardiac arrhythmias, hypokalemia, hyperglycemia, and tremors.

63. What is good about oral delivery?
Oral delivery is easy to use, has a short administration time, provides reproducibility, and offers controlled dosing. However, it has a longer onset of action, systemic side effects, and some drug loss due to first-pass metabolism in the liver.

64. What are the side effects of albuterol?
Side effects include tremors, cardiac effects, tolerance to bronchodilator effects, loss of broncho-protection, CNS stimulation, reduced PaO2, metabolic disturbances, propellant toxicity, and sensitivity to additives.

65. What are the two types of ultra-short-acting drugs used as 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 minutes; Peak: 5-20 minutes; 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 minutes; Peak: 5-20 minutes; Duration: 0.5-2 hours.

70. What are the dosages when prescribing racemic epinephrine?
2.25% solution, 0.25-0.5 mL, or 5.63-11.25 mg, administered 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 Metaprel.

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 for albuterol sulfate?
SVN: 0.5% solution, 2.5 mg QID; (10 mg for K+ treatment). MDI: 90 mcg/puff QID.

75. What are the onset, peak, and duration of albuterol sulfate?
Onset: 15 minutes; Peak: 30-60 minutes; 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 levalbuterol?
Xopenex HFA and Xopenex.

78. What is the dosage amount of Xopenex HFA?
MDI: 45 mcg/puff, administered TID/QID.

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

80. What is the dosage amount of Xopenex?
Adults: 1.25 mg; Pediatrics: 0.63 mg, administered 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 mcg BID

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

88. What are the trade names associated with arformoterol?
Brovana and Foradil Certihaler

89. Where are alpha-adrenergic receptors found when stimulated by epinephrine or norepinephrine?
They are found on smooth muscle membranes.

90. Where are beta-adrenergic receptors found?
Beta-adrenergic receptors are found on cardiac muscles and some smooth muscles.

91. What does Beta 1 (cardiac muscle) stimulation do when activated by epinephrine or norepinephrine?
It increases heart rate and the strength of heart contractions.

92. What does Beta 2 (smooth muscle in the lungs) stimulation do when activated by epinephrine?
It causes vasodilation of certain blood vessels and bronchodilation of 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?
They increase blood pressure (BP), heart rate (HR), and cause bronchodilation.

95. How do drugs like epinephrine and norepinephrine produce contractions of smooth muscle?
They stimulate alpha receptors, causing smooth muscle contractions.

96. What happens when using drugs containing epinephrine that stimulate both alpha and beta receptors?
Stimulation of beta-2 receptors causes relaxation of bronchial smooth muscle, while stimulation of alpha receptors causes vasoconstriction and other sympathetic effects.

97. What do sympatholytic drugs do?
Sympatholytic drugs block the sympathetic system, decreasing blood pressure (BP) and heart rate (HR). They are used to treat hypertension, angina, and certain cardiac arrhythmias.

98. What is the function of alpha receptors?
Alpha receptors generally cause excitation, except in the intestines and central nervous system (CNS), where they cause inhibition or relaxation.

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

100. What does stimulation of alpha sympathetic receptors cause?
Stimulation of alpha receptors causes vasoconstriction.

101. What is the function of beta receptors?
Beta receptors generally cause inhibition or relaxation, except in the heart, where they cause stimulation.

102. Where are beta-1 receptors located?
Beta-1 receptors are located in the heart, where they increase heart rate and contractile force.

103. Where are beta-2 receptors located?
Beta-2 receptors are located in the lungs, bronchial smooth muscle, vascular beds, and skeletal muscle, where they relax bronchial smooth muscle and dilate vascular beds.

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

105. What does epinephrine stimulate?
Epinephrine stimulates both alpha and beta receptors.

106. What does norepinephrine stimulate?
Norepinephrine primarily stimulates alpha receptors.

107. What do parasympathetic vagal nerves innervate?
Parasympathetic vagal nerves innervate the lungs.

108. What do vagus nerves in the lungs release?
Vagus nerves release acetylcholine (ACh).

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

110. What are indications for long-acting agents (salmeterol)?
Long-acting agents are indicated for the maintenance of bronchodilation, control of bronchospasm, management of nocturnal symptoms, and long-term asthma control.

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

112. How long do ultra-short-acting bronchodilators last?
They last less than 3 hours. Examples include epinephrine and racemic epinephrine.

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

114. How long do long-acting bronchodilators last?
They last 12 hours. An example is salmeterol.

115. What does epinephrine stimulate?
Epinephrine stimulates both alpha and beta receptors.

116. Where is epinephrine stored?
Epinephrine is stored in the adrenal medulla.

117. What is the onset of epinephrine?
The onset of epinephrine is rapid.

118. What is the duration of epinephrine?
The duration of epinephrine is short.

119. What is epinephrine typically used for?
Epinephrine is used for acute asthma, post-extubation airway edema, and anaphylactic reactions.

120. What are examples of catecholamines?
Examples of catecholamines include epinephrine, isoproterenol, isoetharine, and bitolterol.

121. What are examples of non-catecholamines?
Examples of non-catecholamines include metaproterenol, terbutaline, albuterol, pirbuterol, and salmeterol.

122. How will a patient’s sputum appear after using aerosols of catecholamines?
The patient’s sputum may appear pink-tinged due to irritation or minor airway bleeding.

123. What are resorcinol and saligenin?
They are beta-2 agonists with an increased duration of action (up to 6 hours), minimal beta-1 side effects, and can be taken orally.

124. What are the adverse side effects of adrenergic bronchodilators?
Adverse side effects include tremors, palpitations, tachycardia, headaches, insomnia, increased BP, nervousness, nausea, tolerance, decreased PaO2 due to shunting, hypokalemia, and propellant-induced bronchospasm.

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

Final Thoughts

Adrenergic bronchodilators play a vital role in managing respiratory conditions by promoting easier breathing and improving overall quality of life.

Their ability to quickly relieve airway constriction makes them indispensable in emergency and long-term treatment settings. However, proper usage, dosing, and monitoring are essential to ensure safety and effectiveness.