Respiratory drugs

Question 1

Doxapram is and used for

Answer 1

Resp stimulants
Emergency drug
Brain stimulant
Stimulates breathing if apnea (stopped) or bradypnea (very slow)
Reverses respiratory depression caused by CNS depressants (e.g., premeds and anesthetics)
Can use with opioid-induced respiratory depression if antagonists not available*
1 drop under tongue of C-Sec. puppies

Question 2

Side effects of Doxapram

Answer 2

S/e: due to non-specific brain stimulation (aggression, tremors, seizure; also ↑BP, arrhythmia)

Question 3

When to use doxapram and how

Answer 3

1 drop under tongue of C-Sec. puppies
Doxapram is 2nd choice to true reversal
Naloxone if opioid pre-med
Yohimbine, Antisedan if alpha-2 premed

Question 4

Antitussives are and when to use

Answer 4

Used to treat non-productive (dry) coughs
E.g. Collapsing trachea; tracheitis from kennel cough, heart enlargement (heart pushes on trachea)
Stops cough by blocking the cough reflex

Question 5

How do antitussives work

Answer 5

Centrally acting – act on the cough center located in the brainstem
Local acting – soothe and coat the mucus lining where there is inflammation/trauma/irritation so signals not sent to cough center

Question 6

Locally acting antitussives are and ex

Answer 6

Not as common in veterinary patients.
Buckley’s Zev OTC for horses and dogs.
-May have some herbs that test positive at competition.
-Label advised stop use 4 days prior to competition.

Question 7

Centrally active antitussives are

Answer 7

Stop cough by blocking the cough center in the brainstem

Question 8

Examples of centrally acting antitussives

Answer 8

Dextromethorphan (DM)
Opiods

Question 9

Dextromethorphan (DM) as an centrally active antitussive

Answer 9

Not controlled. Easily found OTC
Benylin®-DM, Robitussin®-DM
Often mixed with other drugs incl. acetaminophen, ibuprofen (must read labels)

Question 10

Opioids as a centrally acting antitussives

Answer 10

Excellent cough suppression. More effective then DM. Controlled. Can be addictive; risk of owner abuse
Antitussive dose has no respiratory depression, minimal analgesia, possible constipation with chronic use, may see mild sedation
Butorphanol (“Torb”), Hydrocodone (Hycodan®), Codeine

Question 11

Expectorants and mucolytics are and used for

Answer 11

For productive cough - Increase fluid secretion in airways or reduce viscosity of airway mucus= mucus easier to remove
Keep patient hydrated, inhaled steam helps too

Question 12

Guaifenesin is and used for

Answer 12

Expectorants and mucolytics
expectorant in human OTC cough meds.
Mostly used for anesthesia in veterinary patients.

Question 13

Sodium iodide is and used for

Answer 13

Expectorants and mucolytics
Cattle and horses given IV
Not in pregnant or hyperthyroid patients

Question 14

Dembrexine (Sputolysin) is and used for

Answer 14

Expectorants and mucolytics
oral powder for horses
Mucolytic and some antitussive properties

Question 15

Acetylcysteine (Mucomyst®) is and how to use

Answer 15

Expectorants and mucolytics
Human product
Oral, IV, nebulized
More commonly used to treat acetaminophen toxicity in cats.

Question 16

Decongestants work for what receptors

Answer 16

α1 receptor agonists = vasoconstriction of vessels in mucus membranes =↓edema and secreons
BUT, most have some β1 receptor activity therefore cause ↑HR as a side effect.
Commonly found in human cough/cold medications

Question 17

How to treat asthma

Answer 17

Remove any allergic triggers and dust
Anti-histamines; used more as a prevention than treatment
Dilate airways - bronchodilators
Very mild effect with anti-histamines
Reduce inflammation
Steroids- fluticasone (Flovent®), prednisolone, dexamethasone

Question 18

Anti-histamines (H1-blockers) are

Answer 18

Diphenyhydramine (Benadryl®) OTC human label, oral and injectable
Pyrilamine– powder labelled for horses (with ephedrine)
Histamine released by mast cells triggers acute inflammation & bronchoconstriction
Drugs block histamine binding to receptors
Better for long-term prevention than treatment; used in COPD, allergy, asthma

Question 19

Antihistamine side effects

Answer 19

Side effects: sedation; anticholinergic effects (e.g., dry mouth)

Question 20

Options for type of bronchodilators

Answer 20

Widen the bronchi to increase airflow
Many options:
Beta-2 adrenergic agonists
-Most commonly used
Methylxanthines – ex. aminophylline, theophylline
-CNS stimulation. Think “caffeine”
Anticholinergics (atropine)
-Emergency/CPR bronchodilator
Antihistamines
-Very mild bronchodilation; inhibits the histamine response that causes the inflammation

Question 21

Beta-2 adrenergic agonists as bronchodilators are

Answer 21

Airway irritation leads to bronchoconstriction
Βeta 2-adrenergic agonists bind to and activate the beta-2 receptors in the lungs causing bronchodilation & stabilize mast cells = less histamine release.

Question 22

Salbutamol (Ventolin®), terbutaline, albuterol is what type of drug and used how

Answer 22

Beta 2 adrenergic agonists
Given with an MDI dispenser (puffer) in small animals
Local administration decreased dose and systemic side- effects

Question 23

Indications of beta 2 adrenergic agonsits

Answer 23

Indications: collapsing trachea, asthma
Side-effects: stimulation of β1-receptors in the heart = ↑HR

Question 24

Beta 2 adrenergic agonists for equine asthma are

Answer 24

Clenbuterol (Ventipulmin®) – oral syrup/injectable – equine
Caution at end of pregnancy – reduces uterine contractions.

Question 25

Methylxanthines are

Answer 25

Theophyline, aminophylline
Related to caffeine, theobromine (in chocolate)
Available in injectable and oral form

Question 26

Why are Methylxanthines used less often than B2 agonists

Answer 26

More Side effects: GI irritation (vomit, nausea), CNS stimulation (excitement, tachycardia);
Can alter liver metabolism of other drugs
Low TI so easy to overdose

Question 27

Steroids are used for what in resp

Answer 27

No bronchodilatory effect
Used to treat the inflammation component of lung disease
Feline/Equine asthma
Infection or neoplasia where edema and inflammatory are damaging lungs)
Can be given systemically (more side effects – don’t use in breeding horses) or as an inhaler

Question 28

Side effects of steroids for resp

Answer 28

Side-effects depend on dose and chronicity (see previous notes). Inhaler has fewest side effects, but can increase risk of secondary airway infection.

Question 29

Fluticasone is used for

Answer 29

available as an inhaler (Flovent®)
$$$$
Can be used chronically along with a β2-adrenergic agonist. Always give the β2-agonist first

Question 30

Why is local delivery of airway drugs preferred

Answer 30

Increased concentration at site of action
Decreased systemic side effects
Faster onset of action
Local delivery is preferred route of delivery of beta-2 adrenergic agonists and steroids for treatment of asthma/COPD
Goal is to inhale into bronchi and bronchioles (i.e., lower airways)

Question 31

How to deliver airways drugs locally

Answer 31

Nebulizer
Measured-dose inhaler (MDI)

Question 32

Metered dose inhalers are

Answer 32

“Puffers”
Drug is placed in a pressurized container that delivers a set quantity per dose ie. mcg/activation
Need a SPACER for animals

Question 33

How to use a spacer on a metered dose inhaler

Answer 33

Dose is aerosolized into chamber with one way valve which animal inhales over a few breathes
Mask must be fitted to animal for tight-seal
Cats cover entire nose
Horses one nostril
Hold spacer to nose for 10 sec afterwards/or count breaths.

Question 34

How to use a metered dose inhaler for horses to stop them from getting spoked

Answer 34

Squeeze puffer first away from the horse then apply to their nose.

Question 35

Nebulizers are and how are they used

Answer 35

solutions/suspensions are transformed into fine mists → inhaled through mouth or nose → deposited onto surface of bronchiolar epithelium
Chamber, mask or ETT (if heavy sedation of GA)
Don’t forget diuretics can also help move fluid out of the lungs