Cough Treatment Overview

Cough Treatment Overview

• Cough is a forceful expulsion of air from the lungs, often an involuntary, protective reflex.
• Coughs can be caused by the expulsion of respiratory secretions, foreign particles, irritants, or excessive mucus in the airways.
• Coughs can also be symptoms of underlying respiratory or cardiovascular conditions.

Cough Mechanism

• Coughs are initiated by stimulation of mechanoreceptors or chemoreceptors in the throat, respiratory passages, or stretch receptors in the lungs.
• Impulses are sent to the cough center in the medulla.
• Efferent impulses travel through parasympathetic and motor nerves to the diaphragm, intercostal muscles, and lungs, increasing their contraction to cause the cough.

Types of Cough

• Acute cough: Lasts less than 3 weeks.
• Chronic cough: Lasts more than 8 weeks.
• Cough can be productive (with sputum) or unproductive (dry).

Common Causes of Cough

• Common cold
• Upper/lower respiratory tract infection
• Allergic rhinitis
• Smoking
• Chronic bronchitis
• Tuberculosis
• Asthma
• Gastroesophageal reflux
• Pneumonia
• Congestive heart failure
• Drug use (e.g., ACE inhibitors)

Treatment of Cough

• Antitussives (cough suppressants):

  • Suppress the cough center in the medulla (central and peripheral effects).
  • Examples: Codeine, pholcodeine, noscapine, dextromethorphan.
  • Codeine: prodrug metabolized to morphine; less addictive; useful antitussive at low doses (<15mg); can cause drowsiness, thickened sputum, and constipation.
  • Noscapine & Pholcodeine: related to papaverine; lack addictive, analgesic, and constipating properties; do not interfere with mucociliary movement.
  • Dextromethorphan: NMDA receptor antagonist; temporary cough relief, especially for minor throat and bronchial irritations. Can cause nausea, vomiting, drowsiness, dizziness, and blurred vision.

• Expectorants:

  • Act peripherally to increase bronchial secretions or decrease mucus viscosity to facilitate removal by coughing.
  • Classified into directly acting (e.g., guaifenesin, sodium/potassium citrate or acetate) and reflexly acting (e.g., ammonium salts).
  • Guaifenesin: increases secretion volume and reduces its viscosity in the trachea and bronchi.
  • Ammonium salts: gastric irritants that reflexively increase bronchial secretions and sweating.

• Mucolytics:

  • Help in expectoration by liquefying viscous tracheobronchial secretions.
  • Examples: Bromhexine, Acetyl cysteine.
  • Bromhexine: thins and fragments mucopolysaccharide fibers; increases sputum volume and decreases sputum viscosity.
  • Acetylcysteine: directly given into the respiratory tract, opens disulfide bonds in mucoproteins of sputum, reducing viscosity. Helpful in cystic fibrosis.

• Antihistamines:

  • Added to antitussive/expectorant formulations, provide symptomatic relief in coughs, but lack selectivity for the cough center, reducing secretions (anticholinergic effect).
  • Suitable for allergic coughs (not asthma).
  • Examples: Chlorpheniramine, diphenhydramine, promethazine.

• Bronchodilators:

  • Example: β2-agonists (salbutamol, terbutaline).
  • Increase the velocity of airflow during a cough; clear secretions.
  • Used when bronchoconstriction is present.

• Pharyngeal Demulcents:

  • Soothe the throat and promote salivation to provide symptomatic relief for dry coughs arising from the throat.
  • Examples: lozenges, cough drops, glycerin, licorice, and honey.

Specific Treatment for Cough

• Etiology (cause) dictates treatment approach.
• Underlying infections require antibiotics, cessation of smoking for smoking/chronic bronchitis related coughs.
  • Further, pulmonary tuberculosis requires antibiotics, while inhaled β2-agonists/ipratropium/corticosteroids, along with antibiotics, nasal decongestants, and antihistamines are effective in addressing asthma and postnasal drip.