Antitussives, expectorants, and respiratory disorders relief drugs
- H.Kitaoka
- Dec 9, 2025
- 5 min read
Coughing is an important defensive reaction to protect the body, but if it continues for a long time, it can interfere with daily life.
In this column, we will explain in an easy-to-understand manner for patients the mechanisms and types of coughs that occur, the causes of chronic coughs, and the antitussives, expectorants, and medications to improve respiratory disorders that are used in treatment.
1. Mechanism of coughing
Coughing is a reflex that occurs to expel foreign objects, phlegm, and irritation caused by inflammation that have entered the respiratory tract (nose, throat, trachea, and bronchi).
The mechanism of coughing
Senses stimuliThe cough receptors in the mucous membranes of the airways are stimulated by foreign objects, inflammation, cold air, phlegm, etc.
Information is transmitted to the brain (medulla oblongata)Information reaches the brain through the vagus nerve and trigeminal nerve.
Cough reflex is triggeredThe brain's "cough center" reacts and sends commands to the chest muscles and diaphragm.
Coughing occursForeign objects are expelled by taking a deep breath, closing the glottis to increase pressure, and then exhaling all at once.
In other words, coughing is a ``reaction that protects the body'' and is often necessary to eliminate the cause.
2. Classification of cough
Coughs can be classified based on the duration and characteristics of the symptoms.
●Classification by period
Acute cough (within 3 weeks)The main causes are colds, acute bronchitis, allergies, and aspiration.
Persistent cough (3-8 weeks)A typical example is post-infectious cough (cough that continues after catching a cold).
Chronic cough (over 8 weeks)Diseases such as asthma, postnasal drip (runny nose dripping down the throat), and gastroesophageal reflux disease may be involved.
●Classification by symptom characteristics
Dry coughA cough without phlegm. It is often caused by throat irritation and tends to get worse at night.Examples: allergies, early stages of airway inflammation, side effects of ACE inhibitors, etc.
Productive cough (wet cough)Coughing up phlegm. Expelling phlegm improves the condition of the airways, so it may be better not to try to stop the cough.Examples: bronchitis, pneumonia, COPD, etc.
3. Diseases and pathological conditions that cause chronic cough
If a cough lasts for more than eight weeks, it is called a "chronic cough." There are many causes, but the most common ones seen in patients include:
●1) Coughing and wheezing
This is a disease in which the bronchi become hypersensitive, causing coughing even with slight irritation. Wheezing may not occur. Treatment with inhaled steroids is required.
●2) Atopic cough
This condition is common among people with allergies and is accompanied by an itchy or tingling sensation in the throat. Antihistamines are used to treat this condition.
●3) Posterior nasal discharge syndrome (UACS)
The runny nose can run down the throat, causing coughing. It is important to treat sinusitis and allergic rhinitis.
●4) Gastroesophageal reflux disease (GERD)
The reflux of stomach acid irritates the mucous membranes of the throat, causing a persistent dry cough. Antacids and lifestyle changes are effective.
●5) Chronic obstructive pulmonary disease (COPD)
The main cause is long-term smoking, and the symptoms include persistent coughing, phlegm, and shortness of breath. Bronchodilators are used.
●6) Drug-induced cough (ACE inhibitors, etc.)
Some high blood pressure medications can cause a dry cough as a side effect.
4About cough suppressants
It is a medicine used to "stop" a cough, especially a dry cough.However, it is important to note that coughing is a necessary reflex, and its use may be avoided in illnesses where it is better to expectorate phlegm.
●(1) Type of drug
① Centrally acting cough suppressants
It acts on the cough center in the brain to suppress coughing.
Narcotic: Codeine, dihydrocodeine
Non-narcotic: Dextromethorphan, tipepidine, etc.
Although it has a strong effect, caution is required regarding side effects and dependency issues.
② Peripheral antitussives
This medicine relieves irritation of the respiratory tract mucosa and reduces the occurrence of cough reflexes.Examples: rebamipide, partial effects of carbocisteine, tranexamic acid, etc.
3) Bronchodilator (antitussive as part of its action)
It relieves coughing by widening the airways and making breathing easier.Examples: beta-2 agonists, theophylline, etc.
●(2) How to use cough suppressants
When you can't sleep because of a dry cough
When coughing interferes with daily life
When the cause of the cough is clear and cough suppression is deemed safe
*If you have a wet cough that produces a lot of phlegm, trying to stop the cough forcibly may prevent the phlegm from being expelled, which may worsen your symptoms.
●(3) Side effects and contraindications
Main side effects
Drowsiness, dizziness
constipate
nausea
Respiratory depression (narcotic cough suppressants)
Dependence (codeine-based)
■ Contraindications (examples of when not to use)
During an asthma attack
Diseases that require the expulsion of excess phlegm
Patients with respiratory depression
Children under 12 years of age (codeine-based drugs)
●(4) Precautions for administration to elderly people
Elderly people are more likely to experience the following side effects, so careful handling is required.
Drowsiness → risk of falling
Constipation → worsening of comorbidities
Risk of aspiration
Respiratory depression
Therefore, it is common to start with a small amount and use only the minimum amount necessary.
5Mechanism of sputum production
Phlegm is a mucus produced by the mucous membranes of the respiratory tract in response to foreign substances, bacteria, viruses, inflammation, etc.
Mechanism of increased phlegm
Inflammation causes excessive mucus secretion
Mucus becomes thicker
Weakened airway cilia movement
Difficulty expelling phlegm
Efficient phlegm clearance is also very important in curing infections.
6About expectorants
An expectorant is a drug that makes it easier to expel phlegm.If you have a lot of phlegm, this is often preferred over cough suppressants.
●(1) Mechanism of action and classification
① Mucus regulator (thinning phlegm)
Carbocisteine (Mucodyne)
Ambroxol (Mucosolvan)
Bromhexine
This medicine reduces the viscosity of phlegm and promotes ciliary movement in the airways.
② Expectorant (helps expel phlegm)
Potassium guaiacolsulfonate (MS warm syrup)
Platycodon, Senega (herbal medicine)
It promotes ciliary movement and pushes up phlegm.
3. Airway lubricant (moisturizes the airways)
Saline inhalation
Humid environments
In addition to medication, humidification is also very important.
● (2) How to use expectorants
When you have a lot of sticky phlegm that is hard to cough up
When you need to expel phlegm due to colds, bronchitis, COPD, etc.
When you feel phlegm stuck in your throat and it's painful
Drinking plenty of fluids is known to increase the effectiveness of expectorants.
●(3) Contraindications (examples of when not to use)
If you are allergic to any of the ingredients
Medications that may worsen peptic ulcers
Caution is advised during pregnancy and breastfeeding depending on the type of medication.
Also, if there is blood in the sputum or the condition does not improve for several weeks, you should suspect another disease.
Summary: It is important to choose a cough treatment "according to the cause"
Coughing is a reaction that the body makes to protect itself, so it is not something that can simply be stopped.
Dry cough → cough suppressants
● Cough with a lot of phlegm → expectorant
●Shortness of breath/narrowing of the airways → Medications to improve respiratory disorders (bronchodilators, etc.)
Furthermore, the cause
allergy
Post-infectious inflammation
Acid reflux
respite
COPDIn each case, you will need appropriate treatment.
If you have a persistent cough, do not try to endure it, but consult a medical institution.
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