Asthma pharmacology Flashcards
(38 cards)
What type of respiratory disorder is asthma?
Obstructive
Signs and symptoms of asthma?
Dyspnoea, a feeling of breathlessness
A wheeze, particularly on exhalation (and sometimes heard only on exhalation)
A cough, usually dry, but sometimes productive of thin mucous threads towards the end of an attack
Palpitation or tachycardia
Light-headedness or feeling faint
In moderate to severe asthma (which is not common), you might also see:
Tiredness or drowsiness
Cyanosis
What is allergic asthma?
Acute attacks are triggered by exposure to an allergen, and the attack resolves when the allergen is removed.
In mild to moderate asthma, the airway obstruction is caused by which two factors?
Oedema of the airway walls, narrowing the lumen
Mucus in the airway lumen (both of these features result from the acute inflammatory process in the lungs that is part of an acute asthma attack).
Why does an asthmatic become alkalaemic early on?
Mucus early on is very watery, so carbon dioxide dissolves in it easily.
The patient is hyperventilating because of the asthma, and so carbon dioxide is blown off: the blood CO2 levels fall below normal, and the pH rises.
Patients are alkalaemic at this stage
What happens to mucous if the attack progresses past an acute stage? Why?
Mucus becomes more viscid and less aqueous (as a result of sympathetic stimulation, and perhaps also of dehydration caused by the earlier hyperventilation)
Why does an asthmatic become acidaemic as their attack progresses?
More viscous mucous
Carbon dioxide dissolves in it much less easily, and so the patient begins to retain CO2 and becomes acidaemic.
Why is the cause of breathlessness?
Receptors in the lungs detect the distortion of pulmonary tissue caused by the oedema, and that signal to the central nervous system, resulting in an increased ventilatory effort.
Does hypoxaemia cause breathlessness?
No, only in very late stages
What triggers allergic asthma?
Hypersensitivity reaction.
An allergen triggers a response when it binds to IgE; the bound IgE triggers activation of mast cells in the bronchial epithelium; and histamine is released to start the acute inflammatory process.
What leukocytes are activated and recruited in asthma?
Eosinophils
What T cells recruit eosinophils?
Th2
What effects to stimulated eosinophils have?
Release proteases and perforins, and can cause widespread damage to host tissues
Degranulate very easily
What cytokines may commonly trigger eosinophil activation?
IL-5, IL-13
What are two approaches to asthma treatment?
Symptomatic treatments
Disease modifying drugs
What is a common short acting sympathetic agonist?
Salbutamol
How to sympathetic agonists work?
Bind beta-2 leading to bronchodilation
What is a common long acting sympathetic agonist?
Salmeterol
Why is salmeterol used?
Useful in patients who need salbutamol often: for example, a common indication is in people who often wake in the night needing salbutamol inhalers: a long-acting agonist can offer an uninterrupted night’s sleep for such patients.
What is an alternative type of sympathetic agonist?
Aminophylline (a methylxanthine) inhibitor of phosphodiesterase type III - raises cAMP to amplify any beta-adrenergic stimulation.
How to parasympathetic antagonists work?
Muscarinic antagonists are an alternative approach to sympathomimetics
What is a short acting parasympathetic antagonist?
Ipratropium (a derivative of atropine): short-acting, given by inhaler,
What is a long acting parasympathetic antagonist?
Tiotropium long-acting, less commonly used
What are two ways to give steroids, why give them either way?
Inhaled (e.g. beclomethasone), for mild to moderate asthma and Oral, for severe asthma
