Respiratory Pharmacology Flashcards
How much of an inhaled bronchodilator reaches the lungs
10%
What intracellular mediators result in broncodilation and constriction
Dilation cAMP
constriction cGMP
How are leukotriens produced
Which ones are spasmodic
5-lipoxygenase binds to cell membrane forming a complex with 5LP activating protein. This changes arachadronic acid into leukotrien A4 - this is then used to create any of a whole family of leukotrines of which LTC4, D4 and E4 are spasmogenic
Excretion of salbutamol
Conjugated in liver
Excreted in urine both conjugated and unchanged
Advantages of terbutaline over salbutamol
Other use
Less sympathomimetic side effects
Stimulates surfactant production in neonates
Uterine relaxants in premature labour (all beta 2 agonists)
Dose of nebulised adrenaline for croup or laryngeal oedema
0.5ml/kg of 1:1000 up to max of 5ml!
Effects of inhaled anticholinergic on lungs
Bronchodilatation
Reduced airway resistance
Increased anatomical dead space
Increased physiological dead space
Peak of ipratropium effect and duration
Excretion
2 hrs to peak
4-6 hr duration
Drug into oral tract 70% unchanged into faeces, systemically absorbed metabolism by liver
Aadvantage of tiotropium over ipratropium
Longer half life so can be given just once a day
Perferentially binds to M1 (causing broncodilation) and not M2 (which triggers further ach release) like ipratropium does
Examples of methylxanthines
Caffine, theophylline
Effects of meythlxanthines
Central stimulant effect
Phosphodiesterase inhibition
Facilitates beta 2 action
Enhanced ca release
Adenosine receptor antagonist
Clinical effect of meythlxanthenes
Bronchodilation and increased anatomical dead space
Increased respiratory work with less fatigue (increased rr and muscle work)
Increase in heart rate and cardiac contractility
Reduced pvr
Stimulate gastric acid
Stimulate diuresis
Inhibit uterine contraction
Why is theophylline unpredictable orally
Variable protein binding
Rapid elimination by liver
Difference between aminophylline and theophylline
Aminophylline is more water soluble so can be given iV
Effects of inhaled steroids on resp system
Decreased mucus secretion and oedema
Decreased pvr
Reduced inflammation
Reduced vascular permiabitlih
Stabilisation of mast cells
What is the use of sodium cromoglicate
Mechanism
Membrane stabilisation
Prevention of Bronchospasm only - not treatment
Inhibits platelet activation factor on esonophils, mast cells and platelets
Suppresses axonal simulation from irritants
Bioavailability of cromoglicate
Protein binding
Excretion
1% orally, 10% inhaled
70% bound
Unchanged in urine and bile
Effects of leukotrines on airways
Increase mucus production
Oedema
Eosinophil migration
Bronchoconstriction
Airway hyper responsiveness
Effect of leukotrine receptor antagonist
Block LT1 receptor reducing bronchoconstriction
Block leukotrine production
What sort of asthma is most effectively treated with leukotrine antagonists
Exercise induced and aspirin induced
What is doxapram
Mechanism
Respiratory centre stimulant
Stimulates centrally and at carotid sinus chemoreceptors to increase tidal vol and resp rate
Uses of doxapram
When not to use
Side effects
Useful in patients with central resp depression from resp disease or drug therapy
Not to use with resp obstruction as drive is still there
Side effects include other stimulation eg convulsions anxiety restlessness
Examples of mucolytics
Carbocisteine, Dornase alpha
Origin of surfactant treatment in neonates
Porcine, bovine or synthetic