Respiratory Pharmacology Flashcards
List the structures of the upper and lower respiratory system:
Upper resp
- everything above the larynx
Lower resp
- conducting system (trachea/bronchi) - mucociliary apparatus
- transitional system (bronchioles) - smooth muscle walls that can constrict and dialate
- exchange system (alveoli) -pneumocytes and capillary network
List 5 categories of respiratory disease
allergy/inflammation
pulmonary edema
exercise induced pulmonary hemorrhage
cough
pneumonia
What are the therapeutic goals of treating allergy or inflammatory respiratory disease? What treatments are used to reach these goals?
Goals
- reduce inflammation
- increase mucociliary clearance
- increase gas exchange
How
- steroid/cromolyn sodium
- expectorant/mucolytic
- bronchodilators
What are the therapeutic goals of treating coughing in respiratory disease? What treatments are used to reach these goals?
Goals
- reduce cough
- reduce inflammation
How
- anti-tussive
- steroid
What are the therapeutic goals of treating pulmonary edema in respiratory disease? What treatments are used to reach these goals?
Goals
- reduce fluid
- increase gas exchange
- reduce mucus
How
- expectorant/mucolytic
- diuretic
What are the therapeutic goals of treating exercise induce pulmonary hemorrhage respiratory disease? What treatments are used to reach these goals?
Goals
- reduce trans-capillary pressure
How
- diuretic
What are the therapeutic goals of treating pneumonia in respiratory disease? What treatments are used to reach these goals?
Goal
- reduce infection
- reduce inflammation
- increase gas exchange
How
- antimicrobials
- steroid/NSAID
- expectorant/mucolytic
- bronchodilator
What are 2 mechanisms that can cause pulmonary edema in horses?
cardiogenic
secondary to equine anesthesia
- nares become obstructed (flaccid) and cause increased negative pressure and edema
How is the cough reflex stimulated
stimuli from upper and/or lower respiratory tract via chemo and/or mechanoreceptors
signal the cough center in the medulla
What are the 3 phases of the cough reflex
- inspiratory
- contraction (diaphragm muscles/intercostal muscles/abdominal muscles)
- expiratory (open glottis - causes sound)
What is fluticasone used for in relation to respiratory disease?
It is an inhaled steroid
To treat allergy or inflammatory respiratory disease
How does Pousielles law impact the action of bronchodilators
Pouiselles law
- 4x impact of radius on the resistance
this means that bronchodilator effect is very impactful in reducing resistance
What is the mechanism of action of bronchodilators
It functions by stimulating PSNS receptors in the bronchioles specifically M3 receptor with also beta 2 effects
List 3 types of bronchodilators commonly used
anticholinergics
methylxanthine
beta 2 agonists
What is the mechanism of action of methylxanthine
It stimulated relaxation of smooth muscle by adenosine and phosphodiesterase inhibition
Normally, adenylate cyclase makes cAMP and adenosine inhibits adenylate cyclase. So inhibition of adenosine will increase cAMP
Normally PDE breaks down cAMP. Inhibition of PDE results in increased cAMP
Both mechanisms increase cAMP
- cAMP results in less interaction between actin and myosin
This is because normally, MLCK allow actin and myosin binding. cAMP inhibits MLCK.
It has a narrow therapeutic window
Provide examples of methylxanthine drugs
theophylline*
aminophylline/caffeine/theobromine (in chocolate)
List 2 common situations where antitussives are used in dogs
tracheal collapse or kennel cough
List a common situation in which antitussives are used in horses
BAL
In what situation should you give an antitussive
If the cough is non productive (no swallowing after and tiring to the animal or owner
or diagnostics (BAL)
What is the safest antitussive used in cats
dextromethorphan ( poorly absorbed in dogs)
What is the mechanism of action for dextromethorphan
It is an NMDA receptor antagonist
- in the CNS these receptors these are part of the pain pathway = may have some analgesic effect/improve effects of other drugs
It is an alpha 1 agonist impacting glutamate signalling in the cough center in the medulla
- reduces sensitivity to inputs
It is an opioid derivative but it doesn’t bind opioid receptors
What are the 3 main functions of expectorants
increase bronchial secretions
increase mucociliary clearance
increase productive cough
List 2 examples of expectorants
volatile oils
saline
What is the function of mucolytics
break down mucus
List 3 main mucolytics
acetlycysteine
dembrexine
guaifenesin
What 3 drugs reduce respiratory function
anesthetics
opioids
benzodiazpines
What 3 drugs increase respiratory function
Any CNS stimulant
doxaprom*
almitrine
caffeine
What situation would caffeine be utilized as a respiratory stimulant
dummy foal situation
hypercapnia associated with
- hypoxic ischemic encephalopathy
- neonatal encephalopathy
What is butorphanol used for primarily in the context of respiratory impacts
To reduce cough in horses for BAL
What is another name for acetylcysteine and what is the mechanism of action
Mucomyst
It breaks the disulfide bonds in the mucoproteins because of its free sulfydryl groups
What are 2 potential adverse effects of acetylcysteine
hypersensitivity reaction or bronchoconstriction after inhalation
What are some common uses of acetylcysteine
Infused into guttoral pouches to break up chondroids
Given as enema to foals to break up meconium impaction
break down respiratory mucus and enhance clearance
Used IV to support the liver during acetaminophen or xylitol toxicity
How is acetylcysteine administered
Either via nebulizer (inhale) or IV (to tx toxicity) or enema or infuse guttoral pouch
What is another name for dembrexine? What are its effects?
Sputolysin - a phenolic benzylamine
some antitussive effects
reduce tracheal mucus
no effect on inflammation
there is minimal research
What is dembrexine used for commonly in large and small animals
horses:
- reduce mucus in RAO/IAD/pneumonia
dog
- otitis media (infuse into ear)
How is dembrexine administered
PO
or infused into ear (dog)
What is the mechanism of action for guaifenesin
It is a CNS muscle relaxant
PSNS impact
- vagal stimulation resulting in bronchial secretions
- irritation of gastric mucosa resulting in the gastropulmonary reflex (increases secretion of submucosal glands in airway/mucus hydration)
What are the 2 main impacts of guaifenesin
increased mucociliary function
expectorant impacts
What species can guaifenesin be used in
horse
cat
dog
human
What is triple drip
guaifenesin + ketamine + xylazine
IV field anesthetic
List 3 anticholinergic drugs that can be used as bronchodilators
atropine
glycopyrrolate
hyoscine butylbromide (buscopan)
List 3 beta 2 agonists used as bronchodilators
albuterol
salbutamol
clenbuterol
What is the function of salbutamol and albuterol
short acting bronchodilators
- used for asthmatic flare ups (not chronic use)
If used chronically it can become pro-inflammatory
How is albuteral and salbutamol administered
inhaled
Asthma is most common in which animal species
cats and horses
What is another name for clenbuterol?
ventipulmin
What is clenbuterol primarily used for
Treatment of equine asthma
Use for less than 30 days - max benefit is seen after 14d
Tachyphylaxis (reduced efficacy) and sometimes rebound hypersensitivity is seen if administration occurs >21d of continuous administration
What is commonly combined with administration of clenbuterol (or even albuterol/salbutamol) to increase efficacy?
environmental change - reduce exposure to allergen
What is the mechanism of action of doxapram
CNS stimulant
stimulated chemoreceptors in the carotid artery and aorta resulting in reflex stimulation
directly stimulate respiratory centers in brain
What is the physiologic impact of doxapram administration
increased respiratory rate and volume
no impact on arterial PaO2 (potentially because the increased respiration results in increased O2 demands)
reduce arterial PaCO2
