Pharmacology 3 - COPD and Rhinitis Flashcards
Is airflow obstruction reversible in COPD?
Little or no reversibility (compared to reversible airway obstruction in asthma)
What is the pathogenesis of COPD?
Cigarette smoke and other noxious chemicals stimulate resident alveolar macrophages (possibly also influenced by CD8+ lymphocytes)This causes the release of neutrophilic chemotactic factor, IL-8, LTB4 and O2 radicalsThese cause the activation of neutrophils, and more macrophages and CD8 T cells These release proteases (matrix metalloproteinases) and free radicalsThis leads to chronic bronchitis and emphysema
What do matrix metalloprotineases cause in terms of bronchitis? (symptoms of chronic bronchitis)
They causes inflammation of bronchi and bronchioles, cough, clear mucoid sputum, infections with purulent sputum
What do matrix metalloprotineases cause in terms of emphysema? (symptoms of emphysema)
Distension and damage to alveolarDestruction of acinial pouching in alveolar sacs
What 3 different types of muscarinic acetylcholine receptors do human airways contain?
M1, m2, m3
What nerve is the preganglionic neurone that supplies the bronchial smooth muscle?
Vagus nerve (No sympathetic innervation_
What receptors are located in the ganglia of the parasympathetic branch which is supplying the airways? (2)
nAChR (nicotinic receptors)M1 receptors (mediate a slow excitatory post synaptic potential that increases action potential frequency resulting from nicotinic receptor stimulation)
Where is M2 located and what does it do (in terms of parasympathetic supply to airways)?
Located on the postganglionic neurone terminals (acts as inhibitory auto receptors reaching release of ACh)
Where is M3 located and what does it do (in terms of parasympathetic supply to smooth muscle)?
Present on smooth muscle and mucus-secreting cellsmediates contraction and increased secretion
Apart from the drugs in the guidelines, what do drug do doctors sometimes prescribe patients who have difficult to control asthma?
Muscarinic antagonists
What happens when ACh activates M3 muscarinic receptors on airway smooth muscle cells?
Through Gq, PLC (phosopholipase C) is activated which converts PIP2 to IP3 IP3 binds to the IP3 receptor on the sacroplasmic reticulum (basically a ligand gated ion channel)This causes calcium to diffuse into the cytoplasm leading to contraction
How do muscarcinic acetylcholine receptor antagonists work?
They are block the M3 muscarinic receptor, meaning ACh cannot bind leading to contraction of the smooth muscle (bronchoconstriction)
Are muscarcinic acetylcholine receptor antagonists currently used competitive or non-competitive?
Competitive
What are the 2 categories of competitive muscarinic receptor antagonists current licensed?
Short acting muscarinic antagonists (SAMAs)Long active muscarinic antagonists (LAMAs)
What are the 2 SAMAs currently licensed?
IpratropiumOxitropium
What are the 2 LAMAs currently licensed?
TiotropiumAclidinium
How are all the muscarcinic receptor antagonists given?
Inhalation
What feature of muscarinic receptor antagonists reduces absorption and system exposure avoiding multiple potential adverse effects?
Quaternary ammonium group
How long is the onset of action of muscarinic ACh receptor antagonists roughly?
Delayed (grater than 30 mins)
What effect do using macaroni ACh receptor antagonists have? (3)
Relax bronchospasm caused by irritant stimuli (irritants initiate a vagal reflex that liberates ACh) Also block Ach-mediated basal toneDecrease mucus secretion
Do muscarinic ACh receptor antagonists have any effect on the development of COPD?
Only have a little effect - their effect is mainly palliative
Why do muscarinic ACh recepto antagonists have few adverse effects?
Due to the possession of a quaternary ammonium grou
What is the main disadvantage of ipratropium?
It is a non-selective blocker of M1, M2 and M3 receptors
Why is Tiotropium functionally selective for M2 muscarinic receptors?
It has a greatly longer half life at the M3 muscarinic receptor - Aclidinium works in the sam way
Why is block of M2 by muscarinic antagonists not desirable?
Release of ACh from parasympathetic post-ganglionic neurones is increased (M2 acts as a pre junctional inhibitory auto receptor - activaiton by ACh inhibits further ACh release)
Are b2-adrenoceptor agonists used to treat COPD?
Yes - they provide some bronchodilation although have no effect on underlying inflammation (both LABAs and SABAs)
What is indaceterol?
A recently licensed “ultra-LABA” that has rapid onset of action (unlike salmeterol)
What is superior to using either a LABA or a LAMA along?
A combination of a LABA and a LAMA (e.g. salmeterol/ tiotropium) - superior to either drug separately in increasing FEV1 - recommended for moderate COPD
What are MABAs?Advantage of these?
Muscarinic antagonist B2-agonistsLABA/ LAMA combinations are likely to be most effective when both drugs are deposited in the same location in the airways - MABAs are a novel approach that are attempting to develop ligands that possess both LABA and LAMA activity within the same molecule