An over-the-counter (OTC) cough suppressant, or antitussive, is a medication formulated to quiet the body’s cough reflex. These products work by acting on the cough center in the brain to raise the threshold at which a cough is triggered. Determining the “best” suppressant requires selecting the correct type of medication for the specific kind of cough being experienced, as selecting the wrong product can be ineffective or counterproductive.
Distinguishing Between Cough Types
Coughs are categorized as productive or non-productive. A non-productive cough is commonly known as a dry cough, often described as hacking or irritating, and does not bring up mucus or phlegm. This type of cough is typically caused by irritation in the throat or airways and is the primary target for cough suppressants.
A productive cough is characterized as wet or chesty because it brings up mucus or sputum from the lungs. This wet cough is the body’s natural mechanism for clearing the respiratory tract of excess secretions or irritants. Suppressing a productive cough can hinder this necessary clearing process, which is why antitussives are only indicated for dry, non-productive coughs.
Primary OTC Suppressant Ingredients
Dextromethorphan (DXM)
The primary active ingredient classified as an antitussive available over the counter is Dextromethorphan (DXM). DXM works centrally by acting on the cough center in the brain, decreasing the sensitivity of cough receptors and interrupting the transmission of the cough impulse. This mechanism offers temporary relief from a dry, irritating cough.
DXM is structurally similar to codeine but lacks significant affinity for the mu-opioid receptor, minimizing its addictive potential at therapeutic doses. It is commonly found in products like Delsym and Robitussin CoughGels, often dosed between 10 mg to 30 mg every four to eight hours for adults. Its antitussive effect typically begins within 15 to 30 minutes and lasts up to six hours.
Diphenhydramine
Another ingredient sometimes used for cough suppression, particularly for nighttime relief, is Diphenhydramine. This first-generation antihistamine works by crossing the blood-brain barrier and suppressing the medullary cough center. Diphenhydramine’s significant side effect of drowsiness is why it is frequently included in “nighttime” formulations. While it suppresses coughs, its anticholinergic properties can dry up secretions, which may be counterproductive if mucus is involved.
When Suppression Is Not Recommended
Cough suppression is not recommended when the cough is productive, meaning it involves thick, wet mucus. The cough reflex serves a protective role, helping to expel secretions that could lead to lower respiratory tract complications. Using a suppressant inhibits the body’s ability to clear these secretions, potentially trapping mucus and creating an environment conducive to secondary bacterial infections.
For a productive cough, the appropriate treatment is an expectorant, such as Guaifenesin. Guaifenesin works by irritating the gastric mucosa, which increases the volume and reduces the viscosity of respiratory tract secretions. By thinning the mucus, Guaifenesin makes the cough more efficient at clearing the airway. Therefore, if the cough is wet and chesty, a product containing Guaifenesin (like Mucinex) should be selected instead of an antitussive.
Safe Usage and Medical Red Flags
Dosage and Interactions
Safe usage requires strict adherence to dosage instructions. Taking more than the recommended amount, especially DXM, can lead to serious side effects and potential abuse. It is advisable to avoid combination products unless all symptoms require treatment, as this reduces the risk of accidentally overdosing on a single ingredient.
Caution must be exercised regarding drug interactions with DXM, which affects serotonin reuptake. DXM should not be taken within 14 days of using a Monoamine Oxidase Inhibitor (MAOI), such as certain antidepressants, due to the risk of serotonin syndrome. Individuals taking other serotonergic agents, like Selective Serotonin Reuptake Inhibitors (SSRIs), should consult a doctor before use.
When to See a Doctor
Self-treatment with cough suppressants is intended only for temporary relief of common cold symptoms. OTC suppressants are not appropriate for chronic coughs or those caused by underlying conditions like asthma or chronic bronchitis. Professional medical attention is needed if the cough exhibits any of the following red flags:
- The cough persists for more than seven days.
- It is accompanied by a fever above 101°F.
- Symptoms include shortness of breath or blood in the mucus.