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Chapter 9
Respiratory System Drugs
Copyright © 2011 Delmar, Cengage Learning
Basic Anatomy and Physiology
• The respiratory system is the body system
that brings oxygen from the air into the
body for delivery via the blood to cells
• Respiration is the exchange of gases
between the atmosphere and the cells of
the body
• Ventilation is the bringing in of fresh air
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Basic Anatomy and Physiology
Copyright © 2011 Delmar, Cengage Learning
Respiratory Conditions
• Respiratory conditions are categorized into
upper and lower respiratory conditions
– Upper respiratory conditions in animals are mainly
caused by infectious agents that produce clinical
signs such as congestion and coughs
– Lower respiratory conditions in animals include
asthma, bronchitis, pneumonia, and chronic
obstructive pulmonary disease (COPD)
• COPD in horses is commonly called “heaves”
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Respiratory Drugs
• Expectorants
– Increase the flow of respiratory secretions to
allow material to be coughed up from the
lungs
– Increase the fluidity of mucus
– An example is guaifenesin
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Respiratory Drugs
• Mucolytics
– Decrease the viscosity or thickness of
respiratory secretions
– An example is acetylcysteine
(also used to treat acetaminophen toxicity)
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Respiratory Drugs
• Antitussives
– Suppress coughs
– May be centrally acting or locally acting
– Centrally acting antitussives include
butorphanol, hydrocodone, codeine,
dextromethorphan, and trimeprazine (in a
combination product)
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Respiratory Drugs
• Decongestants
– Decrease the congestion of nasal passages
by reducing swelling
– Examples include phenylephrine and
pseudoephedrine
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Respiratory Drugs
• Bronchodilators
– Widen the lumen of the bronchi and counteract
bronchoconstriction
– Examples include cholinergic blocking agents
(anticholinergics such as aminopentamide, atropine,
and glycopyrrolate), beta-2-adrenergic agonists (such
as epinephrine, isoproterenol, terbutaline, and
albuterol), and methylxanthines (such as
aminophylline and theophylline)
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Respiratory Drugs
• Antihistamines
– Block the effects of histamine
– Antihistamine drug names usually end with –
amine
– Side effects include CNS depression and
anticholinergic effects such as dry mouth
– Examples include diphenhydramine and
chlorpheniramine
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Respiratory Drugs
• Respiratory stimulants
– Stimulate the animal to increase its
respirations
– Examples include naloxone (usually used to
stimulate respiration following narcotic
overdose) and yohimbine (used to reverse
xylazine administration or overdose)
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Asthma Drugs
• Glucocorticoids:
– anti-inflammatory drugs administered orally or by inhalation
– Orally used to treat feline asthma
– Inhaled used to decrease swollen and narrowed airways by
decreasing inflammation
– There are fewer side effects with inhaled glucocorticoids than
with oral ones
• Bronchodilators:
– Used in addition to glucocorticoids in the treatment of feline
asthma
– Side effects include tracheal or bronchial irritation
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Asthma Drugs
• Methylxanthines:
– Another group of bronchodilators used in the
treatment of feline asthma
– Have a narrow therapeutic index
• Cyclosporin:
– A fungal derived protein useful in the allergic
response in feline asthma
– Side effects include nephrotoxicity and vomiting
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Chronic Obstructive Pulmonary
Disease (COPD) Drugs
• Is treated by using some forms of medication
and keeping good management practices:
–
–
–
–
Keeping horses outside as much as possible
Reducing dust
Storing hay in a dry place
Improving ventilation in horse stables
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Chronic Obstructive Pulmonary
Disease (COPD) Drugs
• Glucocorticoids help decrease smooth muscle
contraction, suppress inflammation, and reduce
mucus production
• Inhaled glucocorticoids are used to decrease
swollen and narrow airways
• Bronchodilators relax the smooth muscles of the
airways
– Can also be combined with other anti-inflammatory
drugs
Copyright © 2011 Delmar, Cengage Learning