Respiratory Pharmacology Flashcards
How does the cough reflex work? What stimulates it?
afferent arc receives input from sensory nerves in the bronchial and tracheal airways to activate the cough center in the medulla oblongata
foreign bodies or excessive mucus on the surface of the airways
How do opioids work as antitussives? What are the main 2 used? What is the point of administering them before surgery?
directly depress the cough center in the medulla by acting on mu or kappa opiate receptors
- Butorphanol (Torbutrol) - kappa receptor agonist
- Codeine - mu receptor agonist
provides a sedative effect, analgesia, and facilitates intubation by decreasing associated laryngeal spasms and coughing
Why is Codeine only occasionally used in dogs? How does Hydrocodone compare to Codeine?
oral absorption is low and inconsistent
same mechanism of action, more potent
What 3 drugs is Hydrocodone combined with?
- Hycodan - anticholinergic
- Homatropine - discourages abuse
- Acetaminophen
Why is the oral availability of Butorphanol low? How does it compare to Codeine?
first pass metabolism —> oral doses are higher than parenteral doses
maximum effects are reached within 4 hours and persists for 10 hours —> Codeine’s effect is much shorter
What are 5 uses of β-adrenergic agonists in animals?
- airway disease
- allergic bronchitis
- feline asthma
- recurrent airway obstruction (RAO - heaves)
- inflammatory airway disease (IAD) in horses
What is the mechanism of action of β-adrenergic agonists in the respiratory system?
stimulates bronchial smooth muscle, leading to increased activity of adenylate cyclase and cAMP —> smooth muscle relaxation and bronchodilation
What 2 additional effects do β-adrenergic agonists have other than bronchodilation?
- release of inflammatory mediators on mast cells (little effect on other inflammatory cells)
- increase mucociliary clearance in the respiratory tract
What is the main clinical use of β-adrenergic agonists as bronchodilators?
short-term relief of bronchospasm
- repeated administration (several weeks) may diminish response by causing desensitization —> change the receptor!
What short-acting nonspecific bronchodilator is commonly used? What is it considered the drug of choice for?
Epinephrine
emergency treatment of life-threatening bronchoconstriction (anaphylactic reactions)
What are 3 long-acting β2-specific bronchodilators commonly used?
- Terbutaline
- Albuterol
- Clenbuterol
How does Terbutaline compare to Isoproterenol? How is it used in horses?
longer acting (6-8 hours)
treats recurrent airway obstruction (RAO) —> injectiable
What are the 2 isoforms of Albuterol? How is it administered to horses?
- R-isofomrm
- L-isoform: bronchoconstriction and proinflammatory
insertion of a nasal bulb into the horse’s nostril, which is activated when the horse inhales
What is Clenbuterol approved for use in? How does it compare to other β-agonists?
bronchodilator for horses with RAO
lower clinical efficacy —> partial agonist
What are the 2 most adverse effects of β-agonists? In what agonists is this especially common?
tachycardia and muscle tremors
- β1-agonists
- high doses of β2-agonists
What is Cromolyn? What activity does it lack? When must it be administered?
sodium cromoglycate - stabilizes mast cells in hypersensitive airways by inhibiting their release of histamines and leukotrienes
bronchodilation
before the horse is exposed to the allergen (prophylactic)