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Questions and Answers

Which of the following best describes the action of beta-2 agonists?

Inhibit cAMP levels and enhance smooth muscle contraction

Increase cAMP leading to relaxation of smooth muscle (correct)

Directly block the release of catecholamines from the adrenal medulla

Stimulate vagus nerve to induce bronchoconstriction

What is the primary therapeutic action of theophylline related to smooth muscle?

Decreases cAMP levels

Enhances PDE enzyme activity

Inhibits adenosine receptors (correct)

Directly stimulates bronchial secretions

Which of the following medications is used as a uterine relaxant?

Ritodrine (correct)

Salbutamol

Ipratropium bromide

Caffeine

What is a common side effect associated with theophylline usage?

Tachycardia Signup and view all the answers

What is the mode of action of ipratropium bromide in respiratory treatment?

Blocks vagus-mediated bronchoconstriction Signup and view all the answers

Why should theophylline be administered carefully to patients with heart failure?

It may provoke arrhythmias Signup and view all the answers

Which condition is NOT a listed use for beta-2 agonists?

Chronic bronchitis Signup and view all the answers

What characteristic distinguishes methylxanthines like theophylline from beta-2 agonists?

Methylxanthines possess a narrow therapeutic margin Signup and view all the answers

What is the primary characteristic of bronchial asthma?

Increased airway responsiveness to stimuli Signup and view all the answers

Which class of drugs is primarily used as bronchodilators in asthma treatment?

β adrenergic agonists Signup and view all the answers

Which of the following can serve as a potential trigger for asthma attacks?

Physical exercise Signup and view all the answers

What is the duration of action for short-acting β2 adrenoceptor agonists used in asthma?

4-6 hours Signup and view all the answers

Which of the following medications is classified as a mast cell stabilizer?

Nedocromil Signup and view all the answers

Which of the following side effects is commonly associated with β adrenergic agonists?

Tachycardia Signup and view all the answers

What role does immunotherapy play in the management of asthma?

Reduces airway inflammation over time Signup and view all the answers

Which of the following is NOT typically considered a supportive therapy in asthma management?

Antihistamines Signup and view all the answers

Study Notes

Drug Therapy of Bronchial Asthma

Bronchial asthma is a chronic inflammatory airway disease characterized by increased responsiveness to various stimuli. Airways narrow, causing inflammation and changes in severity.
Asthma attacks involve recurrent reversible airway obstruction triggered by different stimuli. Symptoms include coughing, wheezing, and difficulty breathing.

Pathogenesis of Asthma

Asthma involves contracted smooth muscle in the airways.
Blood vessels in the airways are infiltrated by immune cells.
Inflammation and swelling occur.
Excess mucus is produced.
Reduced airway diameter.

Management of Asthma

General Measures:
- Stop smoking
- Avoid triggers (antigens, severe exercise, stress, certain medications like aspirin)
- Treat related conditions like chest infections and use immunotherapy where appropriate
Drug Treatment:
- Bronchodilators:
  - Beta-2 adrenergic agonists (short-acting: e.g., salbutamol; long-acting: e.g., salmeterol)
  - Methylxanthines (e.g., theophylline)
  - Anticholinergics (e.g., ipratropium bromide)
- Anti-inflammatory Agents:
  - Glucocorticoids
  - Leukotriene receptor antagonists (e.g., zafirlukast, montelukast)
  - Anti-IgE monoclonal antibodies
- Supportive Therapy:
  - Expectorants and mucolytics
  - Treatment of respiratory infections
  - Sedatives and tranquilizers
  - Oxygen therapy and fluid therapy
  - Desensitization

Bronchodilators

Mechanisms of Action (Beta-2 Agonists): Beta-2 agonists increase cyclic AMP (cAMP), leading to relaxation of bronchial smooth muscle.
Mechanisms of Action (Methylxanthines): Methylxanthines (like theophylline) inhibit phosphodiesterase (PDE), increasing intracellular cAMP and relaxing smooth muscles. They also reduce the release of bronchospasm mediators.
Mechanisms of Action (Anticholinergics): Anticholinergics (like ipratropium bromide) block acetylcholine's effect on airways, preventing bronchoconstriction.

Beta-2 Agonists

Classification:
- Selective (e.g., salbutamol): Fewer side effects
- Non-selective (e.g., adrenaline, isoprenaline, ephedrine)
Short-acting (e.g., salbutamol): Effective during acute attacks. Lasts 4-6 hours.
Long-acting (e.g., salmeterol): Prophylactic for preventing future attacks; last 12 hours.
Dynamics (of Beta-2 agonists): Increased cAMP, leading to relaxation of smooth muscles, reduced mucociliary transport, reduced release of bronchospasm mediators and reduced microvascular permeability
Salbutamol: Synthetic, sympathomimetic catecholamine that works via inhalation, oral, or parenteral routes. Causes bronchodilation, reduced bronchial secretion, mast cell stabilization, and uterine relaxation.

Methylxanthines

Examples: Theophylline, theobromine, caffeine
Kinetics: Oral, sustained release, intravenous, inhalation, rectal
Dynamics: Inhibits phosphodiesterase (PDE), increasing cyclic AMP (cAMP), leading to smooth muscle relaxation. Reduced adenosine receptors, inhibition of antigen-histamine release, and increased catecholamine release from the adrenal medulla.
Narrow therapeutic index: Careful monitoring of serum levels is crucial.

Adverse Effects of Theophylline

Cardiovascular (tachycardia, arrhythmia)
Central Nervous System (convulsions, nervousness)
Gastrointestinal (heartburn, vomiting, abdominal pain, peptic ulcer)

Precautions of Theophylline

Intravenous administration should be slow to avoid cardiac arrhythmias, hypotension, and arrest.
Lower infusion rates in patients with heart failure, liver dysfunction, or elderly individuals.
Avoid a loading dose if theophylline has been taken recently.
Oral preparations should be taken with food to prevent gastric irritation.
Serum levels should be checked regularly (eg, approximately every 6-12 months).

Anticholinergic Agents

Ipratropium Bromide: A quaternary amine; fewer side effects (inhalation).
Mechanism of Action: Blocks vagal-mediated bronchoconstriction.
Use: COPD, chronic bronchitis, emphysema, psychogenic asthma, asthma induced by beta blockers.

Leukotriene Antagonists

Ziluton: Inhibits 5-lipoxygenase, preventing leukotriene synthesis.
Zafirlukast & Montelukast: Block leukotriene receptors.
Use: Effective in exercise, antigen, and aspirin-induced asthma.

Anti-IgE Monoclonal Antibodies

Mechanism of Action: Inhibits mast cell degranulation, also might inhibit IgE synthesis by B lymphocytes
Use: Decreases asthma severity and reduces corticosteroid needed by patients with moderate-to-severe asthma.