Respiratory Drugs Flashcards
what is the pleural cavity?
potential space existing around each lung
negatively pressurized at all times
what does narrowing of airway cause?
increased airflow and more irritation and reflex bronchoconstriction
what is the main active stimulator of bronchoconstriction and secretion?
parasympathetic input
what does sympathetic input cause?
bronchodilation
beta2
what are the positives of inhalation therapy?
achieves high local concentrations
may minimize systemic exposures and hence adverse effects
what are the main disadvantages of inhalation therapy?
ensuring accurate dose is delivered
knowing what the dose should be in the first place
what class of drugs is used as antitussives?
opiates
when should you not use an antitussive?
productive cough and/or bacterial pneumonia
how do opioid antitussives reduce the cough?
decrease responsiveness of cough center to afferent stimuli and may decrease peripheral response of sensory nerve endings
mu and kappa receptors
what opioid antitussives do we use?
butorphanol
hydrocodone
codeine
diphenoxylate and atropine
what effects does butorphanol have?
weak analgesic
effective cough suppressant
what receptors does butorphanol impact?
partial mu receptor agonist and full kappa receptor agonist
is dextromethorphan an opioid?
no: structurally related to but does not bind opioid receptors
what receptors does dexstromethorphan stimulate?
sigma-1 receptors
which antitussive do we use in cats?
dextromethorphan is safest
what is the mechanism of action for mucolytics?
breakdown mucous secretions
what is the mechanism of action for expectorants?
increase bronchial secretions
enhance mucociliary clearance
promote productive cough
what is one mucolytic?
acetylcysteine
how does acetylcysteine work?
interacts with disulfide bonds on mucoproteins to break down mucous
enhances mucous clearance
increases glutathione
why is acetylcysteine used as an anti-dote for some toxicants?
increases glutathione concentrations or reacts directly with toxic metabolites
what is the predominant system for control of bronchiole tone?
parasympathetic
what is the primary adrenergic receptor for control of bronchiole tone?
beta-2
what are the actions of beta-2 agonist bronchodilators?
smooth muscle relaxation
decrease release of inflammatory mediators from mast cells
decrease and thin secretions
increase mucociliary clearance (activate cilia)
what does chronic stimulation of beta-2 receptors result in?
down-regulation and de-sensitization of receptors
what enhances response to beta-2 agonists?
corticosteroids
what does down-regulation and de-sensitization of beta-2 receptors lead to?
variable response to beta-2 agonists
what can peripheral beta-2 activation lead do?
vasodilation
hypotension
reflex tachycardia
who is clenbuterol approved in?
horses
banned in food animals: was used as tocolytic and growth promotant
which species is terbutaline preferred for?
cats
injectable
what is the mechanism of action of theophylline?
adenosine receptor antagonist
inhibits phosphodiesterase (increase cAMP)
augments release of catecholamines
what do methylxanthines cause?
airway smooth muscle relaxation
decreased release of inflammatory mediators from mast cells
increased mucociliary transport
in what can methylxanthines be used?
occasionally feline asthma
cardiogenic cough in dogs: enlarged left atrium pushes on bronchi
collapsing trachea in dogs
what are respiratory stimulants used for?
decrease respiratory depressant effects of opiates and barbituates
“dummy” foals to correct hypercapnea
what does doxapram do?
stimulates respiratory center
activates aortic/carotid chemoreceptors
what do mast cell stabilizers do?
stabilize mast cells and prevent release of inflammatory mediators
may inhibit platelet-activating factor (early and late phases of pulmonary inflammatory response)
what do glucocorticoids do?
upregulate beta-adrenergic receptors and increase their sensitivity: increase synthesis of intermediary protein in second messenger system of receptors
what is the clinical use of mast cell stabilizers?
must be administered prior to triggering exposure
the lungs are found within the ___________ cavity, not the ______________________
thoracic
pleural cavities
_____________________ can increase sensitivity to nociceptors, leading to bronchoconstriction, and increase secretions, thereby narrowing airways
inflammatory mediators
histamine, prostaglandins, leukotrienes
what are the sites of action of drugs affecting the respiratory system?
lung tissue
alveoli/bronchioles/bronchi
pleural cavity/space
membranes
autonomic nervous system
CNS: cortex and cough center
what must you use for aerosol drugs?
metered-dose inhaler products with an appropriate spacer
what do we want to do with inflammatory/allergic airway diseases?
decrease inflammation/immune response
promote air exchange by increasing bronchi and bronchiole diameter
improve mucociliary clearance
what classes of drugs do we use in inflammatory/allergic airway diseases?
anti-inflammatories
bronchodilators
what do we use in exercise-induced pulmonary hemorrhage?
diuretics
what are antitussives used for primarily in horses?
diagnostic procedures
equine asthma
what is the cough reflex?
afferent nerve endings in bronchi and trachea: irritation and stretch, vagus nerve
activate cough center in medulla oblongata
what is the response in opioid antitussives?
inconsistent
significant adverse effects
what might hydrocodone come with?
homatropine: prevent human abuse
antimuscarinic effects
which hydrocodone products should you not use?
those with acetaminophen in them
what is the detailed mechanism of action for mucolytics (acetylcysteine)?
interacts with disulfide bonds on mucoproteins to break down mucous
enhances mucous clearance
increases glutathione
with beta 2 agonists, what might non-selective agonists do?
activate beta 1 and cause tachycardia and arrhythmias
what activity does terbutaline have?
beta 2 agonist
minimal beta 1 activity
can you use terbutaline orally in horses?
no
low bioavailability
can you use the racemic mixture of albuterol chronically in cats?
no
S-isomer pro-inflammatory
what is theophylline/aminophylline?
adenosine receptor antagonist: bronchodilation, respiratory stimulation
what do methylxanthines stimulate?
respiration centrally
diaphragmatic contractions
CNS excitement/toxicity
what will happen if respiratory stimulants are over-used?
loss of stimulatory effect and loss of respiration
what is cromolyn?
mast cell stabilizer
may inhibit platelet activating factor
how long do glucocorticoids take in dogs to have an effect on upregulating beta-adrenergic receptors and increasing their sensitivity?
48 hours
