How does an antitussive work?
The cough reflex is triggered when irritants activate sensory nerves in the respiratory tract, sending signals to the brain's cough center in the medulla oblongata. Antitussives interrupt this process through central or peripheral action. Centrally acting antitussives, like codeine and dextromethorphan, raise the cough threshold in the brain. Peripherally acting antitussives, such as benzonatate, numb nerve endings in the airways. This suppression of the cough reflex is beneficial for non-productive coughs that don't involve clearing mucus.
Types of antitussive medications
Antitussive drugs are categorized as opioid and non-opioid classes.
Non-opioid antitussives
These are often available over-the-counter and have a lower risk of dependence.
- Dextromethorphan (DM): Common in OTC cough and cold medicines, DM works centrally to relieve dry coughs from colds or flu. High doses can cause serious side effects and potential for abuse.
- Benzonatate (Tessalon Perles): This prescription medication acts peripherally by anesthetizing stretch receptors in the respiratory tract. Swallow capsules whole to avoid mouth numbness and choking.
- Menthol and Camphor: Found in topical products like ointments and lozenges, their vapors can soothe and suppress coughs.
Opioid antitussives
Stronger and typically requiring a prescription due to addiction potential and side effects.
- Codeine: Suppresses cough centrally but carries risks like sedation and dependency, leading to restricted use and not recommended for children under 18.
- Hydrocodone: A controlled substance used for severe coughs when other treatments fail, with a high addiction potential.
Important considerations and safety
Follow dosage instructions carefully, as overuse can cause adverse effects. Be cautious with combination products to prevent overdose. Consult a doctor before use if you have conditions like asthma or high blood pressure.
Antitussive vs. Expectorant: A comparison
Antitussives and expectorants have different functions, used for different cough types.
| Feature | Antitussive (Cough Suppressant) | Expectorant |
|---|---|---|
| Function | Suppresses the cough reflex | Thins and loosens mucus |
| Best for | Dry, non-productive coughs that don't produce phlegm | Productive, "wet" coughs where mucus needs to be cleared |
| Mechanism | Acts on the brain's cough center or numbs airway nerves | Increases fluid in the airways to make mucus easier to cough up |
| Common Examples | Dextromethorphan (DM), Codeine, Benzonatate | Guaifenesin (Mucinex, Robitussin) |
| Key Outcome | Reduces the urge to cough and allows for rest | Facilitates clearing congestion from the lungs and airways |
Drug interactions
Antitussives can interact with other medications.
- MAO Inhibitors: Dextromethorphan and MAO inhibitors can cause serotonin syndrome and should not be taken together. A two-week gap is needed after stopping an MAOI before using DM.
- CNS Depressants: Opioid antitussives with other CNS depressants increase drowsiness and respiratory depression risk.
- CYP2D6 Inhibitors: These medications can increase dextromethorphan levels, raising toxicity risk.
Conclusion
Antitussives are useful for persistent, non-productive coughs that disrupt sleep or activities. They are not for productive coughs. Choose medication based on symptoms and follow dosage guidelines. Consult a healthcare provider before using antitussives, especially for children, those with health conditions, or those taking other medications. For persistent coughs, seek medical advice to address the cause. Home remedies like honey may offer relief with fewer side effects.
For more information on managing coughs, consider consulting the National Institutes of Health.
