Asthma Flashcards
Pathogenesis of asthma Inflammatory cells Structural cells Mediators Effects
Inflammatory cells - mast cells - eosinophils - Th2 cells - basophils - neutrophils - platelets Structural cells - epithelial cells - smooth mm cells - endothelial cells - fibroblasts - nerves
Mediators
- histamines
- leukotrienes
- prostanoids
- PAF
- kinins
- adenosine
- endothelins
- nitric oxide
- cytokines
- chemokines
- growth factors
Effects
- bronchospasm
- plasma exudation
- mucus secretion
- AHR
- structural changes
Guideline goals for successful asthma management
Current control - control of symptoms - maintain normal activity levels - maintain pulmonary function Future risk - avoid adverse treatment effects - prevent asthma exacerbation - prevent asthma mortality
M3 receptor under stimulation by the agonist Ach mimics what effect?
Bronchoconstriction
Increased bronchial gland secretions
Increased mediator release
Beta 2 receptor under stimulation by the agonist NA mimics what effect?
Bronchodilatation
Mast cell stabilization
Increased mucocilliary clearance
Decreased microvascular permeability
Alpha 1, Alpha 2 receptor under stimulation by the agonist NA mimics what effect?
Bronchoconstriction
Decreased gland secretions
H1 receptor under stimulation by the agonist histamine mimics what effect?
Bronchoconstriction
Inflammatory reaction
5-HT3 receptor under stimulation by the agonist serotonin mimics what effect?
Bronchoconstriction
Beta 2 receptor under stimulation by the agonist bradykinin mimics what effect?
Bronchoconstriction
Pharmaceutical options for asthma treatment
Corticosteroids Leukotriene antagonists Mast cell stabilizers Anticholinergic drugs Theophylline Selective beta 2 adrenergic agonists
Which drug class of asthma pharmacotherapy results in reduced bronchial hyper-reactivity?
Mast cell stabilizers
Which drug class of asthma pharmacotherapy results in decreased response to allergens?
Leukotriene antagonists
Which drug class of asthma pharmacotherapy results aids in prevention of progression of chronic asthma, rescue course in rapidly deteriorating conditions and IV for acute exacerbations?
Corticosteroids
Which drug class of asthma pharmacotherapy results in relief of acute exacerbation and control/prevention of chronic asthma?
Anticholinergic drugs
Theophylline
Selective beta 2 adrenergic agonists
Definition of severe asthma
Asthma that requires treatment w/ high dose inhaled corticosteroids + a second controller and/or systemic corticosteroids to prevent it from becoming uncontrolled or that remains uncontrolled despite this therapy
To qualify:
Asthma diagnosis should be confirmed
Comorbidities should be address
Definition of uncontrolled asthma
At least 1 of the following
- poor symptom control (ACQ consistently >1.5, ACT<20)
- frequent severe exacerbations (>2 burts of systemic corticosteroids in the prev year)
- serious exacerbations (> hospitalization or ICU stay in prev year)
- airflow limitation (FEV1 <80% predicted after withholding bronchodilators
What should you check for in uncontrolled asthma before changing the treatment?
Incorrect diagnosis Significant comorbidities Poor compliance Poor inhaler technique Environmental factors (allergen exposure, occupation, smoking)
Management of refractory asthma
Life-threatening
Most commonly precipitated by URTIs
Hydrocortisone 100 – 200 mg 4 – 8hourly infusion
Nebulised salbutamol 2.5 – 5mg with ipratropium bromide 0.5 mg driven by O2
High flow humidified O2
Intubation & mechanical ventilation prn
Antibiotic treatment of respiratory tract infection
Correct dehydrationand acidosis
Saline + sodium bicarbonate infusion
Inhaled + local corticosteroid options
Beclometasone (Beclate)
Budesonide (Pulmicort)
Ciclesonide (Alvesco)
Fluticasone (Flixotide)
Systemic (oral/IV) corticosteroid options
Prednisone (Meticorten) Methylprednisolone (Medrol) Betamethasone (Celestone) Dexamethasone (Decasone) Hydrocortisone (Solucortef) Triamcinolone (Kenalog)
Indication for corticosteroid use in asthma treatment?
Most effective controller therapy available for asthma
ICS not systemic (severe S/E)
Mechanism of action of corticosteroids in asthma treatment
- Decrease formation of cytokines (esp Th2), eosinophils, macrophages and T lymphocytes - Th2 recruit and activate eosinophils and are responsible for promoting the production of IgE and the expression of IgE receptors)
- Reversing mucosal oedema
- Inhibit the generation of PGE2 and PGI2 by inhibiting induction of COX-2
- Decreases down-regulation of B-receptors
- Decrease permeability of capillaries
- Decrease release of leukotrienes and histamine which cause bronchoconstriction
- Decrease hyperresponsiveness of airway smooth muscle to
sensitive stimuli such as cold, irritants, allergens etc
What is the pathophysiology of cysteinyl leukotrienes in asthma?
Constriction of bronchiolar smooth muscle Airway hyperresponsiveness Plasma exudation Eosinophilic inflammation Increased endothelial permeability Promotion of mucous secretion
Mechanism of action of anti-leukotrienes in asthma treatment?
Selective reversible inhibitors of cysteinyl
leukotrine-1 receptor, thus blocking the effects of cysteinyl leukotrines (LTC4, LTD4, LTE4) (Montelukast, Zafirlukast)
Inhibitor of 5-lipoxygenase pathway (Zileuton)
Anti-leukotriene options for asthma treatment?
Montelukast (Singulair)
Zafirlukast (Accolate)
Zileuton (not available in SA)
Pharmacokinetics of anti-leukotrienes in asthma treatment?
Good oral absorption
90% plasma protein bound
Undergo biliary excretion
Pharmacological response within 24hrs
What are adverse effects of anti-leukotrienes?
Abdominal pain Headache Rash Anaphylaxis Eosinophilia, vasculitis (Churg Strauss Syndrome) Liver dysfunction (rare)
Drug interactions of anti-leukotriene options?
Zafirlukast extensively metabolized by liver (inhibitor of CYP3A4 and
CYP2C9)
Enhances anticoagulant effect of warfarin
Erythromycin + terfenadine combination reduces zafirlukast levels
Theophylline reduces zafirlukast levels
Name options in the short acting beta 2 agonist drug class
Salbutamol (Ventolin) Fenoterol (Berotec) Terbutaline (Bricanyl) Hexoprenaline (Ipradol) Orsiprenaline /Metaproterenol
Name options in the long acting beta 2 agonist drug class
Salmeterol (Serevent)
Formoterol (Foradil)
Indacaterol (Onbrez)
Adverse effects of beta 2 agonists?
Muscle tremors Palpitations Restlessness Nervousness Throat irritation Ankle oedema
Name anti-cholinergic options for asthma treatment and their half life
M3 receptor antagonists
- Ipratropium bromide (t1/2 = 4 - 6 hours)
- Tiotropium bromide (t1/2 = 24 hours)
Slower response than beta 2 agonists
Adverse effects of anticholinergics
Mostly elderly affected Sedation Confusion Hallucination Mydriasis + blurred vision Sinus tachycardia Urinary retention Constipation Dry mouth Parotitis
Name methylxanthine options for asthma treatment
Theophylline
Aminophylline
Caffeine
Oxtryphyline