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RS Pharmacology
Respiratory System Pharmacology-Treatment of Bronchial Asthma
Question | Answer |
---|---|
Late asthmatic response is prevented by: | Corticosteroids |
Which factors trigger asthma? | Exercise / cold air Smoking Stress/anxiety Animal dander Allergens (grass, trees, molds, cockroach) Pollutants (sulfur dioxide, ozone, etc) Fumes/toxic substances Medications (ASA, NSAID’s, others) |
Diagnosis of asthma is done by: | Cough,dysnpea, past and family history- subjectively Reduced FEV1/FVC ratio, FEFR, reversibility with bronchodilators, increase in expired NO - objectively |
Asthma is | A chronic disease Possibly fatal |
Asthma medications are: | NOT addictive DO NOT become ineffective |
How is asthma generally treated? | Oxygen Hydration: Oral or Intravenous Expectorants Antimicrobials |
Examples of Quick relief asthma medications: | Inhaled Short acting Beta-2 Agonists Inhaled Anticholinergics Systemic Corticosteroids |
Examples of Long-term control medications: | Inhaled Corticosteroids Inhaled Cromolyn Na and Nedocromil Oral Methylxanthines (Theophyllines) Inhaled Long-acting Beta-2 Agonists (LABA) Oral Leukotriene modifiers (LTRA) |
Pharmacological actions of Beta 2 adrenergic receptors: | Bronchodilation Tremor Tachycardia Fall in blood pressure Slight fall in plasma potassium |
What is the DOC for acute exacerbations? | Beta 2-Adrenergic Agonists |
Function of Beta 2 adrenergic receptors: | Relax airway smooth muscle Inhibit release of mediators Enhance muco-cilliary activity Decrease vascular permeability Inhibit eosinophil activation |
General characteristics of epinephrine: | Not selective, can stimulate α, β1 receptors Not effective orally Inhalation Subcutaneous( in status asthmaticus) |
General characteristics of isopretenol: | Stimulates β1 and β2 receptors Convenient, pocket- sized multidose inhaler Considerable tachycardia and pounding |
Examples of Short Acting Beta 2-Adrenergic Agonists: | Albuterol Terbutaline Pirbuterol Metaproterenol Isoetharine Ancient Tyrants Pursued Mysterious Iodine |
General characteristic of short acting beta 2 adrenergic agonists: | Beta 2 selective |
Onset of short acting beta 2 adrenergic agonists: | 3-5 minutes. |
Maximal effect of short acting beta 2 adrenergic agonists: | 30-60 minutes |
DOA of short acting beta 2 adrenergic agonists: | 4-6 hours |
Examples of Long Acting Beta 2-Adrenergic Agonists(LABA) | Salmeterol Formeterol |
DOA of long acting beta 2 adrenergic agonists: | 12 hours |
General characteristics of LABA: | Suppress nighttime attacks Controllors with steroids No tachyphylaxis. |
Problems of Metered Dose Inhalers(MDI) | Cap not removed prior to use in some patients Timing of canister actuation to inspiration is critical - only first air gets into the right place. Inspiration too rapid - should take 4 - 5 seconds Nasal inspiration contains no medication |
Short-acting formulations are to be used only | In necessary situations Regular use is associated with tachyphylaxis and diminished control |
Toxicity of beta 2 adrenergic agonists cause: | Nervousness and Anxiety Tremor Tachycardia Increased mortality due to cardiac toxicity |
Pharmacogenetics of Beta 2-Adrenergic Agonists | Patients homozygous for glycine at the B-16 locus of the β receptor improved with regular use of albuterol or salmeterol. Patients homozygous for arginine at the B-16 locus of the β receptor deteriorated with regular use of albuterol or salmeterol |
Examples of Methylxanthines: | Theophylline Aminophylline |
Which drugs were the mainstay treatment for asthma? | Methylxanthines |
How are Methylxanthines administered? | Oral IV |
Methylxanthines are classified as: | CNS stimulants: active ingredients in coffee, tea, and cocoa Cardiovascular stimulants: arrhythmias, Nausea, GIT irritation, diarrhea |
MOA of Methylxanthines: | Phosphodiesterase inhibition Adenosine receptor stimulation Antiinflammatory activity |
Problems with Methylxanthines: | Toxic: CNS, Cardiac, GIT Optimal dosing is difficult Wide inter-individual variation in hepatic metabolism Subject for food and drug interactions (erythromycins and ciprofloxacin) Blood monitoring-required |
What is the half life of Methylxanthines? | 3-16 hours |
Use of low dose theophylline significantly inhibits | Late Asthmatic Reaction (LAR) Airway inflammatory infiltration |
Examples of anti-cholinergic agents: | 1) Atropine 2) Ipratropium Bromide |
Function of atropine: | Reduces secretions and impairs mucociliary clearance leading to impaired clearance of airway secretions |
Ipatropium bromide doesn't: | Impair clearance of airway secretions |
How is ipatropium bromide administered? | As metered dose inhaler and as a solution for nebulization |
Main uses of ipatropium bromide: | Mainly useful for COPD Might be very useful only in special conditions of asthma( beta blocker- induced asthma, resistant attacks, cardiac patients) |
Onset and potency of ipatropium bromide: | Slow onset (10-15 minutes) and low potency |
Examples of Anti-inflammatory Agents and Alternative Therapy: | Coricosteroids Inhibitors of Mast Cell Degranulation Leukotriene Pathway Modifiers Immunomodulatory Agents |
Functions of corticosteroids: | Inhibit the synthesis and release of histamine, PGs and cytokines Suppress the inflammatory process Relax bronchial smooth muscle Enhance beta-adrenergic responsiveness Decrease quantity of secretion Inhibit IgE |
MOA of corticosteroids: | Highly lipophilic Bind to cytosolic receptors Drug-receptor complex enters the nucleus Influence transcription of target genes Decrease transcription of genes coding for pro inflammatory cytokines |
How long do corticosteroids need to work? | Several hours to days |
How are corticosteroids administered? | Orally Injected |
Examples of corticosteroids (oral/injectable) | Cortisone, Prednisolone, Dexamethasone |
When are corticosteroids administered? | Short term use indicated in severe refractory attacks Long term use indicated in ”Steroid Dependant” asthma |
What is the most effective way to avoid systemic adverse effects? | Aerosol treatment |
Examples of corticosteroids administered by inhalation: | Beclomethasone Triamcinolone Flunisolide Budesonide Fluticasone Toxic Boys Brew Furious Fathers |
Local side effects of corticosteroids: | Hoarsness of voice (dysphonia) Sore throat and cough Candida infection |
Systemic side effects of corticosteroids: | Osteoporosis, cataract, glaucoma, growth retardation, adrenal suppression, CNS effects and behavioral disturbances, increased susceptibility to infections, and teratogenicity |
Examples of Inhibitors of Mast Cell Degranulation: | Cromolyn Na and Nedocromil Na |
Functions of IMCGs: | Inhibit the release of inflammatory mediators from mast cells (Mast Cell Stabilizers) Prophylactic for mild to moderate asthma |
How often are IMCGs used? | Regular use ( 4 times daily) |
In what case can IMCGs not be used? | Acute asthma |
MOA of IMCGs: | Phosphorylate a cell membrane protein, so, mediator release is inhibited despite antigen-IgE interaction Might decrease Ca++ Might decrease neural pathways, plasma exudation and inflammation, in general |
Side effects of IMCGs: | None related to the drug |
Leukotrienes are synthesized by: | Mast cells and eosinophils |