Asthma Flashcards
Characteristics of category 1 asthma (4)
Intermittent
Daytime symptoms <2 /week
Nocturnal <2 per month
PEFR >80%
Characteristics of category 2 asthma (4)
Mild persistent
Daytime symptoms 3-4 / week
Nocturnal 2-4 / month
PEFR >80%
Characteristics of category 3 asthma (4)
Moderate persistent
Daytime symptoms >4 / week
Nocturnal > 4 / month
PEFR 60-80%
Characteristics category 4 asthma (4)
Persistent severe
Daytime symptoms continuous
Nocturnal frequent
PEFR <60%
Name 3 examples of short acting B2 agonists.
Salbutamol!
Fenoterol
Terbutaline
Half life of salbutamol
4-6 hours
MOA B2 adrenoreceptor agonists (7-2 direct,4 indirect )
Increase cAMP by stimulating adenylyl cyclase via stimulatory G proteins. cAMP phosphorylates a cascade of enzymes which results in:
• Relaxation smooth muscle
• bronchodilation (direct effect-functional antagonists to reverse bronchoconstriction)
• inhibit release of inflammatory mediators (mast cells,TNF-alpha from monocytes ) (indirect)
• increased mucociliary clearance
• prevent microvascular leakage, therefore limit mucosal oedema
• reduce presynaptic acetylcholine release, preventing reflex cholinergic bronchoconstriction
Route of admin of ß2 agonists
Inhale mostly.
Oral: only children and people unable to use inhalers
Salbutamol can be given as nebuliser, also iv if life threatening.
3 main classes of bronchodilators
- B2 adrenergic agonists (sympathomimetics)
- Anticholinergics (muscarinic receptor antagonists)
- Methylxanthines and PDE4 inhibitors
Indications inhaled ß2 adrenoreceptor agonists
Drug of choice in management acute bronchoconstriction or spasm. Principle management of asthma and COPD.
Contraindications to B2 agonists (3)
Hyperthyroidism
Cardiovascular disease
Arrhythmia
(Caution)
Adverse effects B2 agonists (3)
- Fine tremor
- Tachycardia and palpitations
- Hypokalaemia
- Nervousness, headache (vasodilation), dizzy. ‘
Drug interactions B2 agonists (2)
Corticosteroids - increase R hypok and hyperglycemia
Digoxin and diuretics- increase risk cardiac arrhythmia
Name 2 examples of long acting B2 agonists
Salmeterol!
Formoterol
Half life of salmetorol
12 hours
Name 2 examples of methylxanthines
-Phylline.
Aminophylline!
Theophylline
Bronchodilators
MOA xanthines
Inhibit enzyme phosphodiesterase, which catalyse hydralysis of CAMP to AMP
Therefore increased CAMP - relax smooth muscle → bronchodilation
Also antagonise adenosine at A2 receptors (a potent broncoconstrictor) and has anti-inflammatory activity on t cells by decrease release platelet activating factor (PAF)
Route administration Xanthines
Oral (theophylline)
Aminophylline IV for severe attacks.
Indications methylxanthines
- Second line treatment for acute, severe and chronic persistent asthma !
- Also in children unable to use inhalers
- IV in status asthmaticus (aminophylline)
Contraindications xanthines (3)
Cardiac disease
HT
Hepatic impairment (metabolised by liver)
Adverse effects methylxanthine. 2 GIT, 5 CV, 3 CNS
GIT: nausea, vomit,
Cardiovascular: tachycardia, dysrythmias. Headache, flushing, hypotension (dilate smooth muscle)
CNS: insomnia, tremor, anxiety
What is the therapeutic index of Xanthines?
Very narrow! 10-20 mcg/ml
This causes adverse effects more easily and small increases above therapeutic dose can be toxic and even fatal.
When do methylxanthines become most effective?
6 days after starting
Drug interaction Xanthines
Macrolides. Macrolidies occupy the enzymes involved in theophylline breakdown, increasing the plasma conc. Small increases above therapeutic dose toxic/fatal.
MOA glucocorticoids in treatment asthma (4 nb, 8 total)
INHIBIT INFLAMMATORY CASCADE
• Induce formation lipocortin -1!, which inhibits phospholipase A2. This reduces free arachidonic acid and therefore decreased LEUKOTRIENE
• reduced mucosal oedema and mucous production
• inhibit generation PROSTAGLANDIN E2 and PGI2 by inhibit COX2
• decrease formation CYTOKINES (esp th2), eosinophils, macrophages, T cells, mast cell infiltration
• B2 - adreno receptor upregulation
• decrease permeability capillaries
• decrease hyper responsiveness to sensitive stimuli eg cold, allergens
Indications glucocorticosteroids in asthma (3)
- Most effective controller therapy!
- For asthma (prevent progression), usually in combination with B2 agonists, or severe frequent exacerbations COPD
- rescue course in rapidly deteriorating conditions
- iv for acute exacerbations
Contraindications glucocorticoids (2)
Caution in growing children, systemic and local resp/ear, nose, throat infections
Adverse effects glucocorticosteroids (4)
Oral candidiasis (rinse mouth)
Irritation, hoarseness voice, dysphonia
Suppression hypothalamic-pituitary-adrenal axis: Cushings, HT, diabetes
Headache, skin reactions and bruises, psych, paradoxical bronchoconstriction, hypersensitivity
Name 2 examples of Leukotriene R antagonists
Montelukast!
Zafirlukast