asthma and drugs used in treatment Flashcards
what is asthma?
an condition associated with:
- airway hyperresponsiveness
- reversible airflow limitation
- bronchial inflammation
what are the symptoms of asthma?
- wheezing
- shortness of breath
- cough
- worse at night
what are the triggers for asthma?
- emotion
- diet
- cold air/ exercise
- pollutants (cigerette smoke, dust, fumes)
- exposure to allergens
- drugs (asiprin, beta blockers)
what are the long term aims of asthma treatment?
- abolish symptoms
- maintain optimal lung function
- prevent permenant lung damage
- prevent death from acute attack
- avoid unnecessary side effects
what are the differences between reliever and preventer medication for asthma?
reliever - bronchodilator → relax smooth muscle / widens airway (works rapidly and directly to reverse bronchoconstriction)
preventer - anti-inflammatory → stops response to allergen
give four examples of reliever medication used in asthma
- salbutamol (ventalin) - ß2 adrenoceptor agonist
- salmeterol
- ipratropium
- theophylline
give three examples of preventer medication used in asthma
- beclometasone
- sodium cromoglicate
- montelukast
which target is most appropriate to treating asthma?
ß2 receptors as these are found in:
- lungs
- blood vessels
- muscle spindles
what does salbutamol have a similar structure to?
adrenaline
how can ß2 agonists be given?
inhaled or orally
name two short acting ß2 agonists and explain when they would be given
salbutamol
terbutaline
*inhaled beefore exertion to reduce exercise induced asthma - duration of action 3-5hrs
name two long-acting ß2 agonists and explain when they would be given
salmeterol
formoterol
* only used in patients taking inhaled steriods - can be taken 1-2 times daily - duration of actio 12hrs
what are the side effects of ß2 agonists? explain why these occur
- tremor - ß2 receptors in muscles activated
- increased HR - stimulation of cells in SA node
- reduced K+ (hypokalaemia) - stimulation of sodium/potassium pump
- nervous tension/ headache - activation of ß2 receptors in CNS
how can the systemic effects of ß2 agonists be reduced?
by inhaling drug
what are the doses give for oral and inhaled salbutamol?
oral - 4mg
inhaled - 100-200microgram
name three devices used to deliver asthma drugs
- metered dose inhaler (MDI) - coordination needed
- spacer - more efficient at getting drug into lungs and lower airway
- breath activated inhaler - breath enough to activate
describe the distribution of drug using an MDI device
- 50% initially impacts in mouth
- 10% reaches lungs (target)
- 90% eventually swallowed (explains systemic side effects)
what are the benefits of using an accuhaler?
- less coordination needed to deliver drug
- counter indicates drug doses remaining
describe what a turbohaler is
- dry powder inhaler
- powder stored with a desiccant to keep powder dry
- contains no lactose so no taste
what is a nebuliser and what is it commonly used for?
- air/oxygen blows through drug solution creating a fine mist which is inhaled
- mask used
- commonly used in severe asthma attacks and with children
when would a glucocorticosteroid be used in asthma?
as a preventer
name five glucovorticosteroids that are used via an inhaler to prevent asthma attacks
bedometasone - oral inhalant or nasal spray
fluticasone
mometasone
budesonide - relief begins within 10hrs
ciclesonide
* relief from symptoms can take 3-7 days
why are the systemic effects of inhaled glucocorticosteroids reduced?
poor bioavailablity
what can glucocorticosteroids often be administered in combination with?
ß2 agonists
give two examples of combination inhalers which have a glucocorticosteroid and an ß2 agonist together
symbicort - budesonide / formoterol
fluticasone / salmeterol
what does SMART stand for?
Symbicort Maintance And Reliever Therapy
explain the mechanism of action of glucocorticosteroids (GCs)
- GCs are synthesised from cholesterol allowing them to cross cell membrane
- when inside the cell GCs bind to steroid receptors
- teh dry-receptor complex forms a dimer which can cross into nucleus
- in nucleus the dimer binds to specific DNA sequence inducing or supressing genes
- protein production influenced
- GCs inhibit transcription of COX-2 gene - reducing protein production and inflammation
what are the side effects of glucocorticosteroids?
- local immunosuppression - oral thrush
- local effects on vocal cords - dysphonia (hoarseness)
what is prednisolone used forn and how does it work?
- treats acute asthma attack
- short course - 7 days (high dose)
- continue with high dose inhaled steroid in chronic/severe asthma
- works by: suppressing immune system activity and release of inflammatory mediators
explain the danger of stopping glucocorticosteroids abruptly
results in acute adrenal insuffiency as patients ability to synthesise GCs has been suppressed → leads to patient being unable to maintain a stress response leading to addisonian crisis
what are antimuscarinic bronchodilators and what are they used for?
- short acting (reliever)
- used alonside high-dose inhaled glucocorticosteroids for severe asthma
what is the mechanism of action for antimuscarinic bronchodilators?
- block muscarinic receptors → inhibits bronchconstriction activated by parasympathetic nervous system
given an example of an antimuscarinic bronchodilator and explain its side effects
ipratropium - causes dry mouth and precipitates glaucoma
what are cromones and how do they work?
cromones
- inhibit release of chemicals from inflammatory cells (mast cells) → prevents bronchospasm
- reduces allergen induced responses and bronchospasm during/after exercise
name 2 cromones
- nedocromil sodium
- sodium cromoglicate
* stops mass cells releasing histamine and other chemicals - mainly used in children
what do leukotrienes cause?
- bronchoconstriction
- release of inflammatory cells
- increase in secretions in airways
what do leukotriene receptors antagonists do?
relax airways and prevent inflammation
give two examples of leukotriene receptor antagonists and explain side effects
montelukast
zafirlukast
*causes GI disturbance
when is theophylline (aminophylline) used?
orally or IV in patients with persistant symptoms / severe acute asthma
can theophylline be used with other drugs?
yes - ß agonists and/or steroids
what are the drawbacks and side effects of theophylline?
drawbacks: narrow therapetic window
side effects: increased HR, palpitations, convulsions, headache
explain the mechanism of action of theophylline
- blocks phosphodiesterase enzyme (PDE) which breaksdown into 5’AMP - therefore more cAMP is available to stimulate smooth muscle relaxation
what is omalizumab (xolair) used for and how it given?
- an antibody (given subcutaneously) every 2-4 weeks
- reduces effect of allergen induced reactions
- used in adults with severe allergic asthma not controlled by ß agonists and glucocorticosteroids
what are the side effects of omalizumab?
- bruising
- pain on injection
- small risk of anaphylaxis
what is the mechanism of action of omalizumab?
- antibody inhibits binding of IgE to receptor surface of mast cell and basophils
- prevents release of pro-inflammatory mediators and reduces allergen induced airway reactions
describe the treatment strategy for asthma from mild to severe
- inhaled short acting ß2 agonists (as needed)
- inhaled steroids
- add inhaled long acting ß2 agonists and increase dose of inhaled steroids
- short and long acting ß2 agonists and inhaled steroids and another drug (eg. LTR antagonist)
- continuous or frequent use of oral steriods (and immunosuppressants
what can be substituted for inhaled ß2 agonists in stage 1 of the asthma treatment strategy?
ipratropium
oral ß agonists
theophyllines
describe what therapy would be given in acute asthma attack
- bronchodilators given via nebuliser
- glucocorticosteroids given (oral prednislone, IV hydrocortisone) - route depends on severity
- oxygen therapy needed if O2 saturation reduced (<93%)
- in poor response aminophylline injection (severe, acute attacks)
