Pharmacology of Asthma Flashcards
(64 cards)
What are the goals of asthma treatment?
1) Reducing impairment → reducing symptoms, maintaining normal activities and achieving near normal pulmonary function
2) Minimising risks associated with the disease e.g. asthma exacerbations which puts patients in hospital and adverse effects of medication e.g. steroids
What are the two classifications of pharmacological treatment for asthma?
1) Reliever - short term benefit
2) Controller - long term
How are asthmatic airways blocked?
Blockage with e.g. eosinophils or narrowing by inflammation
What is the first step in asthma treatment?
As needed reliever inhaler (blue) → SABA
Describe use of only as needed SABAs
- SABAs are highly effective for relief of asthma symptoms
- However there is insufficient evidence about the safety of treating asthma with SABA alone
- This option should reserved fr patients with infrequent symptoms (less than twice a month) of short duration, with no night waking due to asthma and with no risk factors for exacerbations
What is step 2 of asthma treatment?
Low dose controller (ICS to control inflammation first line) + as needed SABA
What is step 3 of asthma treatment?
One or two controllers (ICS/LABA) + as needed SABA
What is step 4 of asthma treatment?
Two or more controllers _ as needed SABA
Why is increasing the dose of medication past step 4 not a good idea?
Bc after this, even if you increases the dose a lot, it might make no difference and just have really bad side effects
What is step 5 of asthma treatment?
Higher level care and/or add on treatment
Why are bronchodilators quick relief?
Bc they relax smooth muscle
What are the two types of bronchodilators?
1) Selective beta 2 adrenoreceptor agonists (short and long acting)
2) Anticholinergic/muscarinic receptor antagonists (short and long acting)
How are bronchodilators given?
Inhaled (but SBAA can be given IV in intensive care)
What is an example of a short acting selective beta 2 adrenoreceptor agonists (SABA)?
Salbutamol → works within half an hour but effect is gone after 4h
What are some examples of long acting selective beta 2 adrenoreceptor agonists (LABA)?
Formoterol, salmeterol → last up to 12h
Vilanterol → lasts up to 24h (72h)
What is an example of a short acting anticholinergic/muscarinic receptor antagonist?
Ipratropium (bromide)
What are 2 examples of long acting anticholinergic/muscarinic receptor antagonist?
Tiotropium, umeclidinum
How do SABAs (salbutamol) work?
1) Salbutamol stimulates beta-2 adrenergic receptors (the prominent receptors in bronchial smooth muscle)
2) Stimulation of beta-2 receptors leads to activation of adenyl cyclase leading formation of cyclic AMP from ATP
3) High levels of cyclic AMP relaxes bronchial smooth muscle and also inhibits the release fo bronchoconstrictor mediators e.g. histamine and leukotrienes from mast cells in the airway
What happens to salbutamol in the body?
1) After inhalation, salbutamol reaches the lungs directly and acts within 3-5 minutes with a peak at 15-20 minutes
2) After oral administration, ~50% of salbutamol is absorbed from the gut with a slower onset of action, reaching a peak at ~2 hours after intake
What is the overall duration of action of salbutamol?
4-6 hours → buys time to get to hospital/GP, doesn’t treat asthma
How do anti-cholinergic/muscarinic receptor antagonists work?
Block effects of ACh released from cholinergic parasympathetic nerve fibres to smooth muscle and mucus glands → prevents airway smooth muscle contraction and mucus hypersecretion
(Less effective than BAAs at relaxing smooth muscle)
What are side effects of anti-cholinergic/muscarinic receptor antagonists?
Unusual but can include dry mouth, palpitations (bc anti-cholinergic), headache, dizziness, blurred vision → if it doesn’t help after two weeks, stop
What are the effects of tiotropium?
Increases FEV1 and reduces the risk of severe exacerbations
How does tiotropium work?
It attenuates IL-13-induced goblet cell metaplasia and potentially reduces mucus hypersecretion
