Acute Asthma Pharmacology 1 Flashcards
What factors would lead to a diagnosis of severe asthma?
- Previous near fatal asthma
- Previous admission for asthma
- Requiring three or more classes of asthma medication
- Heavy use of B2 agonist
- Repeated attendances at A&E in the last year
Brief pathophys of asthma (4)
- Airways tighten
- Smooth muscle contraction
- Associated inflammation
- Thickening airway walls
What do we want to achieve from asthma treatment?
- Relaxation of smooth muscle
- increases airway diameter
How can we reduce the constriction of the bronchial wall smooth muscle?
Activation of the B2 adrenoreceptor.
- G protein coupled receptor
- increases cyclic AMP formation
- enhances Ca2+ binding
What are adrenoreceptors?
Receptors in organs and tissues that are stimulated by the sympathetic nervous system.
Catecholamines will bind.
Examples of catecholamines
Adrenaline
Noradrenaline
Dopamine
Salbutamol
A1 Adrenoreceptor found (3)
- Acts on vascular smooth muscle.
- Pupil
- Pilomotor smooth muscle
- attached to hair follicles
A1 Adrenoreceptor action
- Vascular smooth muscle contraction.
- Pupil dilation
- Goosebumps
B1 adrenoreceptor found
Acts on heart
- stimulates rate and force
B2 adrenoreceptor found
Respiratory tissue
Somatic motor (voluntary muscle)
Roles of B2 adrenoreceptor
Bronchodilation
Tremors
Dopamine adrenoreceptors found…
Renal tissue
- relaxes arteries
Noradrenaline (4)
- Predominantly alpha agonist.
- Causes vasoconstriction.
- Increases systolic and diastolic pressure.
- Reflex bradycardia.
Isoprenaline (3)
B agonist.
Vasodilator.
Strongly increases cardiac force and rate.
Reasons why inhaled beta 2 agonist is not working
Patient has very severe asthma, cannot move air into their lungs.
Asthma resistant to drug.
Peripheral resistance
How shut down small vessels in legs and arms are
Describe some corticosteroid induced changes in inflammatory cells?
- Eosinophil numbers decrease.
- Decrease of cytokine release from T-cells.
- Mast cell numbers decrease.
- Decrease cytokine release from macrophage
- Decrease in numbers of dendritic cell
Corticosteroid induced changes in structural cells
- Decrease in cytokine mediator release from epithelial cells
- Endothelial cells leak
- Increase B2 receptor
- Decreased mucus secretion
How do corticosteroids act?
- Altering transcription of proteins.
- Has to go through cell wall.
- Binds to soluble glucocorticoid receptors in cytoplasm.
- Then transported into nucleus.
- –> bind to nuclear receptor
- –> affects transcription and translation
- –> alters protein
- –> causes effect
Why is it important to give corticosteroids immediately when patient is admitted into hospital?
Corticosteroids take time to work!
Even IV hydrocortisone - C-max, top concentration , will still take 6 hrs to see effect
State some examples of drugs commonly prescribed in asthma
Betamethasone
Dexamethasone
Pregnisolone
Describe number of Beta 2 receptors throughout life
Babies under 1 y/o will have fewer b2 receptors.
B2 receptors are not evenly expressed throughout life.
Describe Ipratropium bromide?
Parasympathetic antagonist (anti-cholingeric) - combined with beta-2-agonist, produces increased bronchodilation
Deliver via a nebuliser
If nebulised bronchodilator treatment has not helped what might we use?
IV magnesium sulphate.
DO NOT USE NEBULISED
What are other IV options available is nebulised bronchodilator has not worked?
IV salbutamol
IV aminophylline
- v.toxic tho
Describe the mechanism by which magnesium sulfate produces smooth muscle relaxation
- Thought to enhance Ca2+ uptake in SR.
- Mg co-factor regulating no. enzymatic and cellular activities in body.
- Regulates adenyl cyclase, Na/K ATP-ase
