Antitussives: Mechanism of Action and Examples

Antitussives

• Used in cases when coughing is harmful
• Examples: Codeine, Hydrocodone
• Mechanism of action: Opioids suppress the cough reflex by direct action on the cough center in the medulla
• Also, they have analgesic and drying effects on the mucosa of the respiratory tract, increase viscosity of respiratory secretions, and reduce runny nose and postnasal drip

Non-Opioid Antitussives

• Examples: Dextromethorphan, Benzonatate
• Mechanism of action: Dextromethorphan works in the same way as opioids but has no analgesic properties and no CNS depression
• Benzonatate suppresses the cough reflex by numbing the stretch receptors in the respiratory tract and preventing reflex stimulation of the medullary cough center

Antitussives Indications

• Used to stop the cough reflex when the cough is nonproductive or harmful

Antitussives Contraindications

• Drug allergy
• Opioid dependency
• Respiratory depression

Antitussives Adverse Effects

• Benzonatate: Dizziness, headache, sedation, nausea, and others
• Dextromethorphan: Dizziness, drowsiness, nausea
• Opioids: Sedation, nausea, vomiting, lightheadedness, constipation

Antitussives Nursing Implications

• Perform respiratory and cough assessment and assess for allergies
• Instruct patients to avoid driving or operating heavy equipment due to possible sedation, drowsiness, or dizziness
• Report any of the following symptoms to the caregiver: Cough that lasts more than 1 week, persistent headache, fever, rash

Expectorants

• Aid in the expectoration (removal) of mucus
• Reduce the viscosity of secretions
• Disintegrate and thin secretions
• Example: Guaifenesin

Expectorants Mechanisms of Action

• Reflex stimulation: Drug causes irritation of the GI tract, leading to loosening and thinning of respiratory tract secretions
• Direct stimulation: The secretory glands are stimulated directly to increase their production of respiratory tract fluids

Expectorants Drug Effects

• By loosening and thinning sputum and bronchial secretions, the tendency to cough is indirectly diminished

Expectorants Indications

• Used for the relief of productive coughs associated with:
  • Common cold
  • Bronchitis
  • Laryngitis
  • Pharyngitis
  • Coughs caused by chronic paranasal sinusitis
  • Pertussis
  • Influenza
  • Measles

Expectorants Nursing Implications

• Increase fluids, if permitted, to help loosen and liquefy secretions
• Report a fever, cough, or other symptoms lasting longer than 1 week
• Monitor for intended therapeutic effects

Monoamine Oxidase Inhibitors and Sympathomimetic Nasal Decongestants

• Raise blood pressure

Nasal Decongestants Nursing Implications

• Patients should avoid caffeine and caffeine-containing products
• Patients should report a fever, cough, or other symptoms lasting longer than 1 week
• Monitor for intended therapeutic effects

Cough Physiology

• Respiratory secretions and foreign objects are naturally removed by the cough reflex
• Induces coughing and expectoration initiated by irritation of sensory receptors in the respiratory tract

Types of Cough

• Productive cough: Congested, removes excessive secretions
• Nonproductive cough: Dry cough, most of the time, coughing is beneficial, removes excessive secretions and potentially harmful foreign substances