Respiratory Pharmacology

Question 1

Note: other factors can also dilate and constrict the lower airways

What are the roles of adrenaline and acetylcholine in respiration?

Answer 1

Acetylcholine binds to muscarinic-3 receptors to cause constriction of airway smooth muscle
Adrenaline binds to Beta2-adrenoreceptors and causes broncodilation

Question 2

What are the main causes of respiratory dysfunction?

Answer 2

• Bacterial infection
• Helminth infestation
• Hypersensitivity to inhaled allergens
• Cancer
• Heart disease
  We aim to treat the underlying cause of respiratory dysfunction

Question 3

What are the therapeutic goals of respiratory drugs?

Answer 3

• Stimulate respiration
• Reduce frequency or severity of coughing
• Reduce mucus production and enhance mucocilary clearance
• Reduce bronchoconstriction
• Reduce inflammation

Question 4

How do we stimulate respiration pharmacologically?

Answer 4

Central action altering sensitivity of the respiratory centre to CO2
Central and peripheral action on chemoreceptors

Question 5

What is the role of a cough?

Answer 5

Protective reflex mechanism mediated by:
- Stimulation of irritant receptors in airways
- Stimualtion of the cough centre in the meddular

Question 6

How do we cure a cough?

Answer 6

Antitussives - opioid receptor agonists blocking receptors in the cough centre (medulla) reducing cough symptoms
Only used to treat persistent, non-productive coughing

Question 7

What does respiratory tract disease cause in regards to mucus?

Answer 7

• Excessive amounts of mucus
• Viscous mucus (difficult to clear)
• Damage to ciliated epithelium, resulting in impaired mucociliary clearance

Question 8

How do we treat problems with the mucus?

Answer 8

• Drugs that alter mucus viscosity
• Drugs that alter secretory activity of glands
• Drugs that irritate the mucus membranes causing icreased clearance of mucus
• Drugs that increase secretion of watery mucus (limited therepeutic value)
• Drugs that derease blood flow to the secretory glands (less mucus production)
• Drugs that act sympathomimetic causing release of endogenous noradrenaline from presynaptic nerve terminals

Question 9

What are the consequences of bronchoconstriction?

Answer 9

• Reduced alveolar ventilation (lower PaO2 and raised PaCO2)
• Increased resistance to airflow (in and out of the lungs)
• Chronic constriction = airway remodelling

Question 10

What are the consequences of bronchodilation?

Answer 10

• Increased alveolar ventilation
• Increased airflow due to lower resistance
• Occurs during exercise

Question 11

What are Muscarinic Receptor Antagonists and what do they do?

Answer 11

• Bronchodilators
• Non-selective
• Inhibit vagally induced contraction of airway smooth muscle
• Will not affect airway diameter in normal animals

Adverse Effects:
- inhibition if mucociliary clearance
- Inhibition of GIT function
- CNS stimulation

Question 12

What are B-adrenoreceptor Agonists and what do they do?

Answer 12

Selective Bronchodilators (B2-adrenoreceptors)
- relax the airway smooth muscle by activating B2-adrenoreeptors
Other properties include:
- inhibiton of vascular permeability and swelling
- Inhibition of cell activation
- Improved mucociliary clearance
- Dampens parasympathetic effects

Question 13

What are the adverse effects of B-adrenoreceptor agonists?

Answer 13

• Tachycardia and hypotension (vasodilation)
• Sweating
• Restlesness/excitation
• Muscle tremors
• Hypokalemia

Question 14

What are methylxantines and what do they do?

Answer 14

Bronchodilators
Mechanisms unclear but actions include:
- PDE inhibition
- Adenosine antagonism
- Anti-inflammatory effect
- Direct stimulation of respiratory centre in the CNS

Question 15

What are the adverse effects of methylxantines?

Answer 15

• Tachycardia
• Restlesness/excitation
• Vomiting

Question 16

When would we use bronchodilators?

Answer 16

In respiratory diseases that effect normal bronchodilation