Airway pharmacology is a specialized field focused on the understanding and manipulation of drug actions within the respiratory system.
The drugs used, ranging from bronchodilators to anti-inflammatory agents, are instrumental in altering airway function and providing relief to patients.
As respiratory diseases continue to contribute to global morbidity and mortality, a thorough grasp of airway pharmacology is essential for healthcare professionals to effectively treat patients and improve outcomes.
Get instant access to 25+ premium quizzes, mini-courses, and downloadable cheat sheets for FREE.
What is Airway Pharmacology?
Airway pharmacology is the study of how drugs interact with the respiratory system to treat or manage airway-related diseases and conditions. This branch of pharmacology focuses on understanding the mechanisms of action, pharmacokinetics (how the body processes a drug), and pharmacodynamics (how a drug affects the body) of various medications designed to affect the airways.
Medications commonly studied within this field include bronchodilators (e.g., albuterol, salmeterol), corticosteroids (e.g., fluticasone, budesonide), and anti-inflammatory drugs (e.g., montelukast), among others.
These drugs can come in various forms, such as inhalers, oral medications, or injectables.
Airway pharmacology is not only important for the treatment of chronic conditions but also has applications in acute settings such as emergency rooms, where immediate intervention is often required for issues like acute asthma attacks or anaphylaxis affecting the airways.
Note: Understanding airway pharmacology is crucial for healthcare professionals, including physicians, respiratory therapists, and pharmacists, to prescribe the most effective treatments, manage drug interactions, and monitor side effects to improve patient outcomes in respiratory health.
Types of Orally Inhaled Aerosol Drugs
Orally inhaled aerosol drugs are commonly used in the management of respiratory diseases and conditions requiring immediate drug delivery to the lungs.
These aerosol medications can come in different forms, such as metered-dose inhalers (MDIs), dry powder inhalers (DPIs), and nebulizers
Here are some examples of the most common types of inhaled aerosol drugs:
- β-agonist bronchodilators
- Anticholinergic (anti-muscarinic) bronchodilators
- Mucolytic agents
- Nonsteroidal anti-asthma drugs
- Anti-infective agents
- Inhaled pulmonary vasodilators
β-agonist bronchodilators are a class of drugs that act on the β2-adrenergic receptors in the smooth muscles lining the airways.
Activation of these receptors leads to relaxation of the smooth muscles, resulting in bronchodilation—the widening of the airways.
This provides rapid relief from acute symptoms such as wheezing, shortness of breath, and chest tightness commonly associated with asthma and COPD.
Examples include short-acting agents like albuterol and long-acting agents like salmeterol. Despite their efficacy, overuse can lead to tachycardia, tremors, and increased risk of exacerbations.
Anticholinergic bronchodilators work by inhibiting the action of acetylcholine, a neurotransmitter that causes contraction of airway smooth muscles.
By blocking the muscarinic receptors in the airways, these drugs effectively reduce bronchoconstriction. They are often used in combination with β-agonists for conditions like COPD. Examples include ipratropium and tiotropium.
Anticholinergic bronchodilators are generally slower to act compared to β-agonists but have a longer duration of action. Side effects may include dry mouth and, in rare cases, urinary retention.
Mucolytic agents focus on breaking down the structure of mucus in the respiratory tract, making it easier to expel.
These are particularly useful for conditions where mucus build-up can exacerbate breathing problems, such as in chronic bronchitis or cystic fibrosis.
Examples include acetylcysteine and dornase alfa. These agents work by breaking disulfide bonds in the mucus, effectively reducing its viscosity.
This helps in improving mucociliary clearance, making it easier for patients to breathe. However, their use may be associated with side effects like bronchospasm or irritation of the airways.
Inhaled corticosteroids are anti-inflammatory agents that reduce the swelling and inflammation in the airways.
They are commonly used in the long-term management of chronic respiratory diseases like asthma and COPD to maintain airway patency and prevent exacerbations.
Examples include fluticasone, budesonide, and beclomethasone. These drugs act by binding to glucocorticoid receptors, which in turn modulate gene expression to produce anti-inflammatory effects.
Regular use of inhaled corticosteroids can lead to a significant reduction in the frequency and severity of symptoms, although they may also cause side effects such as oral thrush and hoarseness.
Nonsteroidal Anti-Asthma Drugs
Nonsteroidal anti-asthma drugs, also known as leukotriene modifiers, are primarily used for the prevention and chronic treatment of asthma.
Unlike corticosteroids, they do not have steroid-related side effects. Examples include montelukast and zafirlukast.
These drugs work by inhibiting the action of leukotrienes, lipid-derived compounds that induce bronchoconstriction and inflammation in the airways.
They are generally taken orally and are useful for patients who either cannot tolerate inhaled corticosteroids or require additional control of symptoms.
Possible side effects may include liver dysfunction and neuropsychiatric symptoms such as agitation or depression.
Anti-infective agents for inhalation include antibiotics, antifungals, and antivirals that target respiratory infections directly at the site.
These are particularly useful for treating localized infections in the lungs without subjecting the whole body to the drug, thereby reducing systemic side effects.
For example, tobramycin and aztreonam are antibiotics used in the management of chronic Pseudomonas aeruginosa infections in cystic fibrosis patients.
Inhaled anti-infective agents are administered via nebulizers or dry powder inhalers, allowing for high concentrations of the drug to reach the infected areas.
However, the risk of developing drug-resistant strains exists and must be carefully managed.
Inhaled Pulmonary Vasodilators
Inhaled pulmonary vasodilators, such as nitric oxide or iloprost, act directly on the pulmonary arteries to dilate them, thereby reducing pulmonary vascular resistance.
These agents are primarily used in the treatment of pulmonary arterial hypertension (PAH) and acute hypoxemic respiratory failure, including conditions like acute respiratory distress syndrome (ARDS).
Unlike systemic vasodilators, the inhaled form of these drugs targets the lung vasculature specifically, minimizing systemic side effects like hypotension.
However, their use can be limited by the need for specialized delivery systems and close monitoring to manage potential complications like rebound pulmonary hypertension upon discontinuation.
Summary: Each of these types of orally inhaled aerosol drugs plays a vital role in the management of various respiratory conditions. They operate via different mechanisms, have distinct pharmacokinetic profiles, and come with their own sets of advantages and limitations.
Airway Pharmacology Practice Questions
1. What are the adverse effects of inhaled corticosteroids?
Systemic adverse effects: adrenal Insufficiency, extrapulmonary allergies, acute asthma, HPA suppression, growth retardation, and osteoporosis. Local adverse effects: oropharyngeal fungal infections, dysphonia, cough, and bronchoconstriction.
2. What are the common inhaled corticosteroid brand names?
Azmacort, Flovent, Pulmicort, Advair, and Symbicort
3. What are the side effects of nonsteroidal anti-asthma drugs?
Cromolyn-like: none; Antileukotrienes: headache, dyspepsia, and liver enzyme elevation; Monoclonal Antibodies: injection site reaction and viral infections
4. What are some adverse effects of using adrenergic bronchodilators?
CFC-induced bronchospasm, dizziness, hypokalemia, loss of bronchoprotection, nausea, tachyphylaxis, worsening ventilation/perfusion ratio, and a decrease in PaO2
5. What are some common side effects of using adrenergic bronchodilators?
Tremor, headache, insomnia, and nervousness
6. What are the adverse effects of Spiriva and Atrovent?
Almost none because they are fully ionized
7. What are some examples of inhaled anti-infective agents?
Pentamidine isethionate (Nebupent), ribavirin (Virazole), tobramycin (TOBI), and zanamivir (Relenza)
8. What are the four advantages of using inhaled aerosols?
(1) Aerosol doses are smaller than systemic doses, (2) The onset of drug action is rapid, (3) Delivery is targeted to the organ requiring treatment, and (4) Systemic effects are often fewer and less severe
9. What are the indications for dornase alfa?
It is used to treat patients with cystic fibrosis and aims to reduce the frequency of infections while improving pulmonary function.
10. What are the indications for inhaled corticosteroids?
They are used for the anti-inflammatory maintenance of asthma and COPD.
11. What are the indications for long-acting (maintenance) agents?
They are used for the maintenance and control of bronchospasm and other symptoms of asthma and COPD.
12. What are the indications for nonsteroidal anti-asthma drugs?
They are used to manage mild to severe persistent asthma and as an alternative to steroidal treatments. They do not provide any benefits for acute asthma episodes.
13. What are the indications for racemic epinephrine?
It is recommended for strong α-adrenergic vasoconstriction effects and is used after extubation. It can also be used to treat epiglottitis, croup, or bronchiolitis, and it is administered to help control airway bleeding during an endoscopy.
14. What are the indications for short-acting (rescue) agents?
They are used for immediate relief of acute reversible airflow obstruction caused by asthma or other obstructive airway diseases.
15. What are the indications for using anticholinergic drugs?
They are used for the maintenance of COPD.
16. What are the indications for using combined anticholinergic and β-agonist bronchodilator drugs?
They are used for COPD patients to provide relief for an airflow obstruction. They are also useful in patients with severe asthma who have not responded well to β-agonist drugs.
17. What are the most common devices used to administer respiratory drugs?
MDI (metered-dose inhaler), SVN (small volume nebulizer), and DPI (dry powder inhaler)
18. What are the three phases of drug action?
Drug administration, pharmacokinetic, and pharmacodynamic
19. What are the three types of nonsteroidal anti-asthma drugs?
Cromolyn-like agents (Cromolyn sodium, Nedocromil sodium), antiLeukotrienes (Zarfirlukast, Zileuton), monoclonal antibodies or anti-IgE agents (Omalizumab).
20. What are the two inhaled vasodilators?
(1) Nitric Oxide (INOmax), which is used for the treatment of neonates with hypoxemic respiratory failure, and (2) Iloprost (Ventavis), which is used for the treatment of pulmonary hypertension
21. What does an α-receptor do?
It causes vasoconstriction and has vasopressor effects, such as increased blood pressure.
22. What does a β1-receptor do?
It causes an increased heart rate and myocardial contractility.
23. What does a β2-receptor do?
It relaxes bronchial smooth muscle, stimulates mucociliary activity, and has some inhibitory action on the release of inflammatory mediators.
24. What is a fully ionized drug?
A drug that is not absorbed across a lipid membrane (e.g., Atrovent)
25. What is a muscarinic drug?
A drug that stimulates ACh receptors, specifically at the parasympathetic nerve-ending sites
26. What is the difference between an agonist and an antagonist?
Agonists are the stimulating agents, while antagonists are the blocking agents.
27. What is an isomer?
Isomers are compounds with the same molecular formula but different structural formulas that compare to the structures of albuterol and levalbuterol.
28. What are sympathetic and parasympathetic receptors?
Sympathetic = adrenergic; Parasympathetic = cholinergic
29. What is a prodrug?
A drug that is not active until it is metabolized
30. What is Combivent?
A medication combination of ipratropium bromide and albuterol
31. What is DuoNeb, and what is its proper dose?
Ipratropium Bromide 0.5 mg and Albuterol 2.5 mg, administered with an SVN
32. When should an inhaled corticosteroid be administered during an asthma attack?
This drug class should not be given during an acute asthma attack because it does not provide short-term relief. Inhaled corticosteroids are maintenance medications.
33. What is the brand name for acetylcysteine?
34. What is the brand name for Dornase Alfa?
35. What is the brand name for ipratropium bromide?
36. What is the brand name for tiotropium bromide?
37. What is the drug administration phase?
It describes the method by which a drug dose is made available to the body.
38. What is the mode of action for cromolyn sodium?
It inhibits the degranulation of mast cells, which prevents the release of histamine and other mediators of inflammation.
39. What is the mode of action for inhaled corticosteroids?
They are lipid-soluble drugs that act on intracellular receptors. The full effect takes multiple hours; therefore, they do not provide instant relief.
40. What is the pharmacodynamic phase?
Describes the mechanism by which a drug molecule causes its effects
41. What is the pharmacokinetic phase?
It describes the time, course, and disposition of a drug in the body.
42. What should a patient know about inhaled corticosteroids?
They are not to be used as a rescue drug.
43. Why is it recommended to administer albuterol with Mucomyst?
Mucomyst is known to cause bronchospasm; therefore, a bronchodilator is needed.
44. What is the most common route of drug administration for a pulmonary patient?
45. What are the advantages of inhaled aerosols?
You can use smaller doses compared to the systemic route; the onset of the drug is rapid; the delivery is targeted to the specific organ needing treatment; and there are fewer systemic side effects
46. What are the disadvantages of inhaled aerosols?
There are more variables that can affect the delivered dose, and there is often a lack of knowledge of device performance by the patient and caregiver.
47. Inhaled bronchoactive aerosols are intended for local effects in the airway, but some undesired systemic effects can result from what?
From the absorption and distribution throughout the body
48. What is the difference between a fully ionized aerosol drug and a non-ionized aerosol drug?
A fully ionized drug has little or no systemic side effects (it is not absorbed across lipid membranes). A non-ionized drug does produce systemic side effects (it is lipid-soluble and diffuses across cell membranes into the bloodstream).
49. What is the L/T ratio?
Lung availability/total systemic availability; quantifies the efficiency of an aerosol drug in the lungs
50. Using the L/T ratio, which aerosol delivery method is more efficient?
MDI (46%) works slightly better than DPI (23%)
51. What are drug effects caused by?
The combination of a drug with a matching receptor
52. What is the usual neurotransmitter in the parasympathetic system?
53. What do adrenergic drugs help directly dilate?
The bronchial tree
54. Cholinergic causes what?
55. What are the indications for short-acting adrenergic agents?
They are rescue drugs that are good for approximately four hours and are used to provide relief for an acute airflow obstruction.
56. What are the indications for long-acting adrenergic agents?
They are drugs that will last approximately 12 hours and are used for the maintenance of obstructive lung diseases.
57. What is the most common use of adrenergic bronchodilators?
To improve the airflow in patients with asthma
58. What happens during beta-1-receptor stimulation?
It causes an increase in heart rate and myocardial contractility.
59. What happens during beta-2-receptor stimulation?
It relaxes bronchial smooth muscle tissue, stimulates mucociliary activity, and has some inhibitory action on the release of inflammatory mediators.
60. Why would you choose Xopenex over albuterol?
Xopenex is indicated over albuterol in patients with tachycardia.
61. What is the most common side effect of beta-2 selective agents?
62. How can you evaluate a patient’s response to bronchodilator therapy?
By using pre and post-bronchodilator studies; arterial blood gas (ABG) and pulse oximetry; blood glucose and potassium; and blood pressure
63. What are the two inhaled anticholinergic bronchodilators?
Ipratropium and tiotropium
64. What is combined anticholinergic and beta-agonist indicated for?
Ipratropium bromide and albuterol (DuoNeb) are indicated for the treatment of patients with COPD or asthma.
65. What are the side effects of anticholinergic aerosol agents?
Cough and dry mouth
66. What are the two mucus-controlling agents?
N-acetylcysteine (MucoMyst) and dornase alfa
67. How is N-acetylcysteine administered?
Either by nebulization or direct tracheal installation
68. How does N-acetylcysteine work?
It breaks down the disulfide bonds of the mucus so that the patient can cough it up more easily.
69. What can N-acetylcysteine cause?
It can cause bronchospasm, which is why it should never be given without a bronchodilator.
70. What type of patients are treated with dornase alfa?
71. What is the mode of action of dornase alfa?
It breaks down protein bonds.
72. What is another name for dornase alfa?
73. What is the mode of action of inhaled corticosteroids?
They act on intracellular receptors.
74. What are the three types of drugs that prevent asthma from happening?
(1) Cromolyn sodium, (2) Antileukotrienes, and (3) Monoclonal antibodies or anti-IgE agents
75. What are the indications for nonsteroidal anti-asthma drugs?
They are indicated for the prophylactic management of asthma and offer no benefit for treating an acute airway obstruction.
76. What is pentamidine isethionate?
It is used to treat pneumonia caused by pneumocystis jiroveci, which is seen in patients with AIDS.
77. What is ribavirin?
It is a drug used to treat respiratory syncytial virus (RSV) using a SPAG generator.
78. What is inhaled tobramycin?
It is a drug used to fight pseudomonas aeruginosa in patients with cystic fibrosis.
79. What is inhaled zanamivir?
It is a drug that is used to treat influenza.
80. What is nitric oxide used for?
It is used for the treatment of pulmonary hypertension.
81. The acting length of a bronchodilator refers to what?
It refers to how long the drug lasts.
82. What should be performed before and after the administration of a bronchodilator?
You should test the patient with a peak flow meter before and after administering a breathing treatment to check if the drug is effective.
83. What are the three subgroups of adrenergic bronchodilators?
(1) Ultra-short catecholamine agents, (2) Short-acting non-catecholamine agents, and (3) Long-acting adrenergic bronchodilators
84. What is the major risk of administering a bronchodilator?
The major risk is an increased heart rate. If it increases by more than 20 beats/min, you should stop the treatment and notify the physician.
85. What is the speed of onset for inhaled aerosol drugs?
The onset is rapid.
Airway pharmacology provides the scientific foundation for the treatment of respiratory diseases through targeted pharmacological interventions.
Understanding the mechanisms, pharmacokinetics, and pharmacodynamics of drugs like bronchodilators and anti-inflammatory agents is paramount for the optimized care of patients with airway disorders.
As advancements in this field continue to evolve, keeping abreast of the latest research and clinical guidelines becomes increasingly crucial for the effective management and potential mitigation of respiratory diseases worldwide.
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- Faarc, Gardenhire Douglas EdD Rrt-Nps. Rau’s Respiratory Care Pharmacology. 10th ed., Mosby, 2019.
- “Airway Pharmacology: Treatment Options and Algorithms to Treat Patients with Chronic Obstructive Pulmonary Disease.” National Center for Biotechnology Information, U.S. National Library of Medicine, 11 Oct. 2019.
- Caramori, Gaetano. “Pharmacology of Airway Inflammation in Asthma and COPD.” PubMed, 2003.