4.2 Respiration Pharmacology

Question 1

What receptors control respiration?

Answer 1

M3 - ACh (parasympathetic) = constriction

B2 - Adrenalin = vasodilation

NANC transmitters can dilate and constrict lower airway

Question 2

Causes of respiratory dysfunction

Answer 2

• Bacterial infection
• Helminth infestation
• Allergen hypersensitivity
• Cancer
• Heart disease

Question 3

What are respiratory depressants?

Answer 3

Some drugs depress respiration as a secondary effect (e.g., opioids, barbiturates)

Question 4

What is a cough

Answer 4

A protective reflex mechanism:
- Stimulation of irritant receptors (airways)
- Stimulation of ‘cough centre’ (medullar)

Question 5

How do antitussives (cough suppressors) work?

Answer 5

Opioid receptor agonists react with opioid receptors in medulla to decrease cough relfex (-ve feedback)

Question 6

When should antitussives be used?

Answer 6

Treat persistent, non-productive coughing

Question 7

What are mucolytics?

Answer 7

Assist removal of mucous plugs
- bromhexine: alters mucous viscosity
- Dembrexine: alters secretory activity of glands

Question 8

What are expectorants?

Answer 8

Oral - irritate mucous membranes causing increased clearance of mucous

Inhaled - increase secretion of watery mucous

Question 9

What are decongestants?

Answer 9

Nasal - for upper respiratory tract with profuse secretion

indirectly acting sympathomiemetic
directly acts on 𝛂-adrenoceptros
decreases blood flow to secretory glands, reduces mucous production

Question 10

Effects of bronchoconstriction

Answer 10

• Reduced alveolar ventilation
• Increased resistance to airflow
• Chronic = airway remodelling

Question 11

Effects of bronchodilation

Answer 11

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

Question 12

What causes constriction of airway smooth muscle?

Answer 12

Ach (parasympathetic) acts on M3 receptors

NANC (P and NK-A)

Question 13

What causes dilation of airway smooth muscle?

Answer 13

Adrenalin (circulating) acts on B2 receptors

NANC (VIP and NO)

Question 14

Describe Muscarinic receptor antagonistic bronchodilators

Answer 14

E.g. atropine, Ipratropium
- non-selective
- Inhibit vagally induced contraction

Adverse effects - inhibits mucociliary clearance, GIT function, CNS stimulation

Question 15

Describe 𝛃-adrenoceptors agonistic bronchodilators

Answer 15

E.g., Clenbuterol, Turbutaline, Salbutamol
- 𝛃2 selective
- relax airway SM by activating 𝛃2 receptors
- Inhibits vascular permeability, cell activation
- Improves mucociliary clearance
- Dampens parasympathetic effects

Adverse effects - tachycardia, sweating, restlessness, tremors, hypokalemia

Question 16

Describe Methylxantine bronchodilators

Answer 16

• Phosphodiesterase inhibition
• Adenosine antagonism
• Anti-inflammatory effects
• Direct stimulation of respiratory centre in CNS

Adverse effects - tachycardia, restlessness, vomiting

Question 17

When would bronchodilators be beneficial?

Answer 17

• Infection / inflammation of respiratory tract
• Allergic respiratory disease
• COPD