S11.2 Pharmacology of Airway Control

Question 1

Outline the pathophysiology of asthma

Answer 1

TH2 cells release cytokines, these activate inflammatory cells e.g eosinophil. Causes a type 1 hypersensitivity reaction, leading to airway narrowing as smooth muscle contracts, mucus is produced.

Question 2

What is the step 1 management for asthma?

Answer 2

For mild intermittent asthma; SABA
This relaxes smooth muscle and reverses bronchoconstriction.
E.g salbutamol, terbutaline.

Question 3

What is the step 2 management for asthma?

Answer 3

Inhaled corticosteroids
They improve symptoms and lung function.
Mechanism: transactivation occurs which upregulates B2 receptors. Also transrepression occurs which inhibits production of inflammatory molecules.
E.g beclomethasone, prednisolone

Question 4

What is the step 3 management for asthma?

Answer 4

Add on therapy: LABA
Improve asthma symptoms and lung function, slower onset of action so not for acute attack
E.g salmeterol. Also formoterol (fast onset, long duration).

Question 5

What is the step 4 management for asthma?

Answer 5

Alternative add on therapies:
High dose ICS
Leukotriene Receptor Antagonists
Methylxanthines
Long acting anticholinergics (LAMAs)

Question 6

Describe the features of Leukotriene Receptor Antagonists

Answer 6

E.g montelukast
Block the effect of cysteinyl leukotrienes in the airways (which usually cause bronchoconstriction and mucus secretion etc)
ADRs; angioedema, dry mouth

Question 7

Describe the features of methylxanthines

Answer 7

E.g theophylline, aminophylline
Antagonise adenosine receptors, inhibit phosphodiesterase, increase cAMP.
ADRs; nausea, headache
Levels increased by CYP450 inhibitors

Question 8

Describe the features of long acting anticholinergics (LAMAs)

Answer 8

E.g tiotropium bromide, ipratropium bromide.
Bind to M3 muscarinic receptor and block it’s action (prevent bronchoconstriction)
ADRs: dry mouth, urinary retention

Question 9

What is the treatment for acute-severe asthma?

Answer 9

High flow O2, nebulised salbutamol, prednisolone.

If life threatening or no improvement, consider ipratropium bromide or aminophylline.