Treatment Of Asthma And COPD Flashcards
What is asthma
A chronic inflammatory disorder of bronchial airways that result in airway obstruction in response to external stimuli
How is airway inflammation caused
Antigens elicit the production of IgE antibodies. These antibodies attach themselves to the surface of mast cells and basophils.
Exposure to the same antigen after some time results in antigen-antibody reaction on lung mast cells which trigger the release of histamine and cysteinyl leukotrienes, agents that produce bronchoconstriction, mucus secretion and pulmonary edema.
What other chemotactic mediators are produced by mast cells
Leukotriene B4
Cytokines
Symptoms of asthma
Acute bronchoconstriction
Shortness of breath
Chest tightness
Rapid respiration
Wheezing
Cough
Two classes of anti asthmatic drugs
Bronchodilators
Anti-inflammatory agents
Classes of bronchodilators
B2- agonists
Antimuscarinics
Xanthine derivatives
Classes of anti-inflammatory agents
Corticosteroids
Mast cell stabilisers
Leukotriene antagonists
Anti-IgE monoclonal antibody
Long acting B2 agonists
Mention long acting and short acting B2 agonists
Long acting
- Salmeterol
- Formoterol
Short acting
- Albuterol
- Fenoterol
- Terbutaline
MOA of B-agonists
They bind to B-adrenergic receptors which are abundant on airway smooth muscle cells and stimulate adenyl cyclase and increase the formation of intracellular cAMP, thereby relaxing airway smooth muscles and inhibiting release of bronchoconstricting mediators from mast cells.
Difference between selective and non selective B-agonists
Non selective B-agonists activate both a and B adrenoreceptors while selective B-agonists activate B1 and B2 adrenoreceptors, having higher affinity for B2-adrenoreceptors (the predominant subtype in the airway)
Example of non selective B-agonists
Epinephrine
What is the drug of choice to treat acute anaphylaxis
Epinephrine
What is the time epinephrine takes to work and the duration of action
Within 15 mins
60-90 mins
Disadvantages of epinephrine
- Not effective orally
- Hyperglycaemia
- CVS side effects (tarchycardia, arrythmia, hypertension)
- Not suitable for patients with hypertension and heart failure
Ways to administer short acting B2 agonists
Inhalation
Orally
IV
Subcutaneous
What is the onset and duration of action for short acting B2 agonists
15 to 30 mins
4 to 6 hours
Duration of action for long acting selective B-agonists
12 hrs
Administration of long acting selective B-agonists
Inhalation
What class of drug is used to treat nocturnal asthma
Long acting selective B-agonists
What class of drugs are combined with long acting selective B2- agonists
Corticosteroids
Advantages of long acting selective B2-agonists
- Minimal CVS effects so suitable for asthmatic patients with hypertension or heart failure
What is the MOA of muscarinic receptor antagonists
Block muscarinic receptors (M2, M3)
Examples of Antimuscarinics
Ipratropium
Tiotropium
Administration of Antimuscarinics
Aerosol Inhalation
Which bronchodilators are the main choice in COPD
Antimuscarinics
Examples of xanthine derivatives
Methylxanthines
Theophylline
Adverse effects of theophylline
Gastric pain, vomiting
Tremors
Hypotension
Convulsions
Insomnia
MOA of theophylline
Raised intracellular cAMP by inhibiting phosphodiesterase
- Antagonism of adenosine (a potent bronchoconstrictor) at A2 receptors
What is the MOA of anti inflammatory agents
Reduce the number of inflammatory cells in the airways and prevent blood vessels from leaking fluid into the airway tissues
What do corticosteroids do in the airways
Reduce the number of inflammatory cells in asthmatic airways (eosinophils, T-lymphocytes, mast cells, and dendritic cells)
Achieved by
- suppressing the production of chemotactic mediators and adhesion molecules
- inhibiting the survival in the airways of inflammatory cells
How do corticosteroids perform their job
Inhibition of phospholipase A2
Upregulate B2 receptors
Routes of administration for corticosteroids
Inhalation (budesonide and fluticasone)
Orally (Prednisone)
Injection ( Hydrocortisone and dexamethasone)
Onset of action for corticosteroids
2 to 4 weeks
Maximum action duration
9 to 12 months
List mast cell stabilisers
Nedocromil
MOA of mast cell stabilisers
Stabilization of mast cell membrane
Administration of mast cell stabilisers
Inhalation
Which asthma prophylaxis is more preferred in children than adults
Mast cell stabilisers
Examples of leukotriene receptor antagonists
Zarfilukast
Montelukast
Pranlukast
Examples of anti-IgE antibodies
Omalizumab
MOA of monoclonal antibodies
Prevents IgE binding with it’s receptors on mast cells and basophils leading to decrease in release of allergic mediators
Treatment of COPD
- Inhaled bronchodilators
- Inhaled glucocorticoids
- Oxygen therapy