Pharmacy and Pharmacology Lecture 5 - Drugs Affecting the Respiratory System

Review the anatomy of the respiratory system!

Review the anatomy of the respiratory system!

• Nasal filtration, sneezing, and mucoid exudate

• Gag, cough, and laryngeal spasm

• Mucociliary apparatus

• Bronchoconstriction under control of PSN

Identify the protective measures associated with the respiratory system

Produce gag, cough, and laryngeal spasm

How do the pharynx/larynx act as a protective mechanism of the respiratory system?

Acts as a mucociliary apparatus

How do the trachea/bronchi act as a protective mechanism of the respiratory system?

Bronchoconstriction

How do the lower airways act as a protective mechanism of the respiratory system?

Famciclovir

Antiviral medication that impairs viral replication to treat feline herpes

Arginine synthesis

A necessary amino acid for viral replication

L-Lysine

Antagonizes arginine synthesis to treat feline herpes

Antiviral

Suffix -vir refers to a medication that is

Cough

Suffix -tussive refers to

Antitussive

A drug that prevents coughing

Eupnea

Normal breathing

Antitussives used in pets are only centrally acting because pets cannot use locally acting medications such as cough drops or throat lozenges

Centrally acting medications stimulate receptors in the brain. Are antitussives used in pets centrally acting or locally acting?

Inspissated

Dry secretions that can affect respiration

It is better to encourage productive coughing to expel mucus

Why should antitussives be avoided when treating productive coughs?

• Non-productive cough

• Infectious tracheobronchitis (kennel cough)

• Tracheobronchomalacia (collapsing trachea)

Identify indications for antitussives

Collapsing trachea

Tracheobronchomalacia is also known as

Kennel cough

Infectious tracheobronchitis is also known as

Butorphanol (Torbutrol)

Schedule IV weak mu but strong kappa agonist antitussive drug

Hydrocodone (Hycodan or Tussigon)

Schedule II strong mu agonist antitussive drug

Codeine

Schedule II-III weak mu agonist that is inconsistently absorbed

Stimulate opioid receptors at the respiratory center and cough center which results in a decreased cough

How do opioids such as butorphanol, hydrocodone, and codeine work as antitussives?

First pass effect will render it useless unless given in a large amount

Oral butorphanol is given at 10x the IV dosage because

Dextromethorphan

Non-narcotic antitussive that is poorly absorbed in dogs

Mucolytic

A drug that aids in the breakdown of mucus

Lyse mucous and reduce viscosity so cilia can more easily remove it from the respiratory tract

How do mucolytic drugs work?

Acetylcysteine (Mucomyst)

A drug that can be used orally, IV, or by nebulization as a mucolytic, or used in cats with Tylenol intoxication

Acetaminophen intoxication

Other than being used as a mucolytic, Acetylcysteine (Mucomyst) is known as the antidote to

Cats are deficient in an enzyme called glucuronyl transferase manufactured in the liver and cannot eliminate the drug efficiently

Why are cats so susceptible to acetaminophen intoxication?

Methemoglobinemia

Diminution of the oxygen-carrying capacity of circulating hemoglobin that results in muddy brown mucous membranes and cyanosis

• Methemoglobinemia/uria

• Cyanosis

• Heinz body anemia

• Jaundice secondary to hepatocyte damage

• Swollen face and paws

Acetaminophen intoxication in cats can result in

Heinz bodies

Denatured oxidized hemoglobin associated with intravascular hemolysis

• Induce vomiting if ingestion was recent

• Oxygen therapy if severe cyanosis

• Blood transfusion

• Vitamin K

• Acetylcysteine IV or oral given q 4h for 4-6 treatments

• Vitamin C q 6h PRN for methemoglobinemia

• General supportive care including IV fluids

What is the treatment protocol for acetaminophen intoxication?

Expectorants

Increase fluidity of mucous by watery secretion

• Guaifenesin (glyceryl guaiacolate)

• Saline expectorants such as ammonium chloride or sodium citrate

• Volatile oils (pine or eucalyptus oil) directly stimulate watery respiratory secretions

List examples of expectorants that stimulate coughing as fluid moves up from the lower airway

Gastric irritation stimulates the PSN resulting in increased respiratory secretions

How do saline expectorants such as ammonium chloride or sodium citrate work?

Decongestants that cause both alpha-1 and beta-1 stimulation

Pseudoephedrine and phenylephrine are examples of

Adrenergic

Receptors acted on by norepinephrine

Cholinergic

Receptors acted on by acetylcholine

Mydriasis, and vasoconstriction of precapillary arterioles in skin and abdominal organs

Stimulation of alpha-1 adrenergic receptors cause

Inhibition of release further epinephrine from nerve terminal

Stimulation of alpha-2 adrenergic receptors cause

Increased heart rate and and force of contraction

Stimulation of beta-1 adrenergic receptors cause

Bronchodilation, and dilation of blood vessels in skeletal muscle

Stimulation of beta-2 adrenergic receptors cause

• Increased secretions

• Increased motility of GI tract

• Slower heart rate

• Stimulates urination

• Stimulates bronchoconstriction

• Miosis

A cholinergic muscarinic stimulates

Cholinergic nicotinic

Stimulates voluntary skeletal muscle contraction at the neuromuscular junction between the nerve and skeletal muscle

Constriction of lower respiratory bronchioles prevents foreign material from entering alveoli

How is bronchoconstriction a defensive mechanism of the respiratory system?

Bronchiolar constriction which may produce dyspnea

Toxins or drugs stimulating cholinergic receptors that mimic acetylcholine cause

B2

Agonists that produce bronchodilation, and stabilize mast cells

Histamine

Receptor that causes bronchoconstriction secondary to allergies and inflammation

Serotonin

Receptor that plays a big role in pathogenesis of feline asthma

Epinephrine

Drug used in severe, life threatening feline asthma

D) Dopamine

Which of the following does not play a role in bronchoconstriction?

A) Serotonin

B) Prostaglandin

C) Leukotrienes

D) Dopamine

Beta blockers cause bronchoconstriction

Why should beta blockers never be used in asthmatic cats?

Organophosphate

An insecticide that results in salivation, lacrimation, vomiting, and dyspnea if ingested by household pets

Salivation, lacrimation, urination, defecation, dyspnea, and emesis (SLUDDE)

Identify the signs of organophosphate toxicity

• Oxygen therapy

• General supportive care

• Atropine

• Pralidoxime (2-PAM)

What is the treatment protocol for organophosphate toxicity?

Pralidoxime (2-PAM)

Treatment for organophosphate toxicity that works by attaching to receptors on acetylcholinesterase and blocking the binding of the toxin

Aerokat

An aerosol chamber that helps deliver medication to asthmatic cats

Fluticasone (Flovent)

An inhaled corticosteroid, and the treatment of choice for asthmatic cats

Inhibits cells of the allergic and inflammatory process

(Mast cells, eosinophils, lymphocytes, neutrophils, and macrophages)

How does fluticasone (Flovent) work for treatment of asthma?

Methylxanthines and beta-2 agonists

Identify the two categories of bronchodilators

• Terbutaline (Brethine)

• Metaproterenol

• Albuterol (Ventolin)

List examples of beta-2 agonists used as bronchodilators

Albuterol (Ventolin)

The drug of choice used as a metered dose inhaler to promote bronchodilation

All beta-2 agonists are susceptible to down regulation and first pass effect

Why are bronchodilators more effective when used IV or as an inhaler compared to tablet forms?

Aminophylline (not used anymore)

Methylxanthine bronchodilator that causes smooth muscle relaxation by inhibiting phosphodiesterase

Theophylline (can cause GI signs and cardiac stimulation)

Methylxanthine bronchodilator used primarily in dogs to relax smooth muscle and provide anti-inflammatory effects

Macrolide and fluoroquinolone antibiotics, and phenobarbital

The metabolism of theophylline can be inhibited by