Respiratory Pharmacology Flashcards
what are the three pathological mechanisms of an asthma attack?
Bronchoconstriction
Inflammation
Increased secretions
What can we give to alleviate an asthma attack?
Nebulised salbutamol
Nebulised Atrovent
Hydrocortisone
Adrenaline
Nebulised Salbutamol
B2 adrenoreceptor agonist
Mimics adrenaline release from sympathetic nervous system
B2 is specific to the lungs and has minimal effect on the cardiovascular system
Also referred to as short acting beta agonist (SABA)
Relaxes smooth muscle and causes bronchodilation
Inhibits the release of bronchospasm mediators (histamine, prostaglandins, leukotrienes, cytokines and chemokines) from mast cells
Increases mucus clearance by stimulating cilia
Can occasionally ‘spill over’ into B1 receptors of the heart and cause tachycardia
IM Adrenaline
Adrenoreceptor agonist
relieves bronchospasm in acute severe asthma
Acts at many adrenoreceptor sites throughout the body = widespread effects
Acetylcholine (Ach) receptors
Acetylcholine receptors are referred to as cholinergic, which means “having to do with acetylcholine”
There are two categories of cholinergic receptors:
Nicotinic
Muscarinic
Acetylcholine (Ach) receptors:
Nicotinic receptors
Nicotinic receptors are found in the central and peripheral nervous system and muscle.
Gets its name from nicotine
A key function of nicotinic receptors is to trigger rapid neural and neuromuscular transmission
Acetylcholine (Ach) receptors:
Muscarinic receptors
Muscarinic receptors are found in the brain, heart and smooth muscle
Gets its name from a substance called muscarine
Plays an important role in the contraction of smooth muscle (especially in the airway)
Asthma and Acetylcholine
Parasympathetic nerves exerts a mild broncho-constriction effect and encourages mucous production in the background
Under normal circumstances this isn’t a problem but in an asthma attack, it’s not helpful.
Salbutamol and adrenaline use receptors relating to the sympathetic nervous system
Asthma Treatment pharmacodynamics:
Nebulised Atrovent
Muscarinic antagonist
Blocks action of Ach at muscarinic receptors
Reduces vagal tone
This causes bronchodilation
Takes longer to act than B2 agonist (30 minute onset of action lasting for 2-5 hours)
Hydrocortisone
Inhibits synthesis of asthma mediators (inhibits histamine release)
Increases number of B2 receptors
Mimics endogenous hormone cortisol
Decreases:
Bronchial hyper-responsiveness
Inflammatory reaction
Mucous production / mucosal oedema
Inflammatory cell activation / degranulation
Not a simple agonist/antagonist
Produces differing effects at various sites
Hydrocortisone can be given as a stand alone for those in adrenal crisis or Addison’s disease sufferers
Dexamethasone (oral)
Corticosteroid specifically for the management of mild to sever croup in younger children
use modified Taussig score
has an anti inflammatory effect
some improvement will be seen within the first hour
early administration reduces need for intubation by 80%
GTN in heart failure
LVF can result in pulmonary oedema
GTN is the first drug for this condition
Reduces overall BP allowing alveoli to recover and clear fluid.
