Respiratory Medications Overview

Respiratory Medications

• Antihistamines are used to manage symptoms of respiratory conditions like the common cold, allergies, and upper respiratory infections.

Antihistamines

• Mechanism of Action: Antihistamines block histamine H1 receptors, reducing allergic reactions. Histamine, released by the immune system during an allergic response, binds to H1 receptors in various tissues (skin, respiratory tract, blood vessels). This receptor blockage reduces symptoms like sneezing, itching, nasal congestion, and runny nose.
• Common Examples: Diphenhydramine (Benadryl), loratadine (Claritin), cetirizine (Zyrtec).
• Types:
  • First-generation: Often cause sedation and drowsiness because they cross the blood-brain barrier (e.g., diphenhydramine).
  • Second-generation: Less likely to cause sedation (e.g., loratadine, cetirizine).

Decongestants

• Mechanism of Action: Decongestants stimulate alpha-adrenergic receptors (a1 receptors) on the smooth muscles of blood vessels in the nasal passages, causing vasoconstriction. This narrowing of blood vessels reduces blood flow and nasal swelling, relieving congestion and improving airflow.
• Common Examples: Pseudoephedrine (Sudafed), phenylephrine, oxymetazoline (Afrin).
• Important Considerations:
  • Oral decongestants can cause systemic side effects like increased heart rate and blood pressure.
  • Topical decongestants (e.g., nasal sprays) can cause rebound congestion if used for too long due to tolerance development.

Antitussives (Cough Suppressants)

• Mechanism of Action: Antitussives suppress the cough reflex. This is particularly helpful for dry, non-productive coughs.
• Central action: Central-acting antitussives inhibit the cough center in the brain (medulla oblongata).
• Peripheral action: Peripheral antitussives may reduce respiratory tract irritation.
• Common Examples:
  • Dextromethorphan (most common): A central-acting non-opioid antitussive.
  • Codeine: A central-acting antitussive with opioid properties.
• Important Considerations: Dextromethorphan is often available over-the-counter. Codeine is often used for more severe coughs but has potential side effects and dependency risks.

Expectorants

• Mechanism of Action: Expectorants increase mucus production and reduce mucus viscosity (stickiness) in the airways, making it easier to cough up and clear the airways.
• Common Example: Guaifenesin (Mucinex).
• Important Considerations: It's essential to stay well-hydrated while taking expectorants.

Respiratory Drugs

• Respiratory drugs address conditions including asthma, chronic obstructive pulmonary disease (COPD), allergies, and upper respiratory infections. These medications work through various mechanisms to improve lung function, reduce inflammation, and relieve symptoms.

Bronchodilators

• Bronchodilators relax airway muscles, opening airways and making breathing easier. They are frequently used to treat asthma and COPD.
• Beta-2 Adrenergic Agonists: Stimulate beta-2 adrenergic receptors in the bronchi smooth muscles, leading to bronchodilation.
  • Common Examples: Albuterol (Salbutamol), Levalbuterol (short-acting); Salmeterol, Formoterol (long-acting).
• Anticholinergics (Muscarinic Antagonists): Block muscarinic receptors in the lungs, preventing bronchoconstriction.
  • Common Examples: Ipratropium (short-acting), Tiotropium, Aclidinium (long-acting).

Corticosteroids

• Mechanism of Action: Reduce inflammation in the airways.
  • Inhaled corticosteroids: Used for long-term management of asthma and COPD.
  • Oral/Systemic corticosteroids: Used for short-term flare-ups or severe cases, but carry more side effects (e.g., weight gain, osteoporosis).
• Common Examples: Fluticasone, Budesonide, Beclometasone (inhaled); Prednisone, Methylprednisolone (oral/systemic).

Leukotriene Modifiers

• Leukotrienes are inflammatory mediators involved in asthma and allergic reactions. Modifiers prevent bronchoconstriction, inflammation, and mucus production.
• Leukotriene Receptor Antagonists (LTRAs): Block leukotriene receptors to prevent bronchoconstriction.
  • Common Example: Montelukast (Singulair), Zafirlukast (Accolate).
• 5-Lipoxygenase Inhibitors: Prevent leukotriene synthesis, reducing inflammation.
  • Common Example: Zileuton (Zyflo).

Mast Cell Stabilizers

• Mast cell stabilizers prevent the release of histamine and other inflammatory mediators from mast cells. This is used to prevent allergic reactions.
  • Common Example: Cromolyn Sodium (Intal), Nedocromil (Tilade).

PDE4 Inhibitors

• Mechanism of Action: Block the enzyme phosphodiesterase-4, increasing cyclic AMP (cAMP) levels in inflammatory cells, reducing inflammation, bronchoconstriction, and mucus production.
• Common Example: Roflumilast (Daliresp).

Immunomodulators (Biologics)

• Biologics are newer treatments for severe asthma (especially allergic or eosinophilic) by targeting specific components of the immune system.
• Monoclonal Antibodies: Target specific cytokines or immune cells involved in inflammation.
  • Common Examples: Anti-IgE (Omalizumab), Anti-IL-5 (Mepolizumab, Reslizumab), Anti-IL-4/IL-13 (Dupilumab).

Cough Suppressants (Antitussives)

• Mechanism: Suppress the cough center in the brain.
• Common Examples: Dextromethorphan, Codeine.

Peripheral Antitussives

• Reduce airway irritation from factors like irritants of allergens.

Expectorants (again)

• Increase mucus production and reduce mucus viscosity (thickness). This makes it easier to clear mucus from the airways.
• Common Example: Guaifenesin (Mucinex).

This quiz explores the role of antihistamines and decongestants in managing respiratory conditions. Participants will learn about the mechanism of action, common examples, and differences between first and second-generation antihistamines. Test your knowledge on these vital medications used for allergies and upper respiratory infections!