Introduction
Expectorants are drugs that facilitate the expulsion of mucus from the respiratory tract by increasing the production of mucus and/or reducing its viscosity.
They are used to treat coughs and congestion associated with common colds, bronchitis, and other respiratory illnesses.
Expectorants can be classified into two main categories:
1. Direct-acting expectorants:
These agents act directly on the secretory cells of the respiratory tract, increasing the secretion of mucus and/or decreasing its viscosity.
This increased mucus production and thinning of mucus help to facilitate its removal from the respiratory tract, ultimately making it easier to cough up.
Examples of direct-acting expectorants include:
A. Guaifenesin (glyceryl guaiacolate)
B. Iodides (e.g., potassium iodide)
C. Bromhexine
2. Indirect-acting expectorants:
These agents work by irritating the gastric mucosa, which in turn stimulates a reflex increase in respiratory tract secretions.
The increased secretions help to loosen and thin the mucus in the respiratory tract, making it easier to cough up.
Examples of indirect-acting expectorants include:
A. Ammonium chloride
B. Potassium citrate
C. Sodium citrate
Cough and its type
Cough is a reflex action that helps clear the respiratory tract of mucus, irritants, and foreign particles.It is a vital protective mechanism that helps keep the airways clear and maintain proper respiratory function.
Coughs can be classified into several types based on their duration, the nature of the cough, and the underlying cause:
Acute cough: Lasts less than 3 weeks, often due to viral infections or irritants.
Subacute cough: Lasts between 3 and 8 weeks, may result from lingering infections or other causes.
Chronic cough: Lasts more than 8 weeks, caused by various underlying conditions.
Productive cough: Produces mucus or phlegm, common in respiratory infections or conditions with increased mucus production.
Dry (non-productive) cough: No mucus production, can be caused by viral infections, allergies, irritants, or medications.
Nocturnal cough: Occurs predominantly at night, caused by factors like asthma, postnasal drip, or GERD.
Whooping cough (pertussis): Severe, uncontrollable coughing caused by Bordetella pertussis infection, dangerous for infants and young children.
Potassium iodide (KI):
Preparation:
Potassium iodide can be prepared through the reaction of potassium hydroxide (KOH) with iodine (I2). The chemical reaction is as follows:
2 KOH + I2 → 2 KI + H2O
Properties:
Potassium iodide is a white crystalline solid.
It is soluble in water and has a slightly bitter, saline taste.
KI is an ionic compound, and its melting point is 681°C (1258°F).
It is relatively stable but can undergo oxidation in the presence of air and moisture, turning yellow due to the liberation of iodine.
Uses:
Potassium iodide is used as a nutritional supplement to prevent iodine deficiency and associated conditions, such as goitre and hypothyroidism.
In medical settings, it can be used as a protective agent against radioactive iodine exposure, particularly in the case of nuclear accidents.
KI is also used in the treatment of certain skin conditions, such as sporotrichosis and erythema nodosum.
It finds applications in the photographic industry, as a component of some photographic chemicals and developers.
Storage:
Potassium iodide should be stored in a cool, dry place, away from heat and direct sunlight.
It should be kept in a tightly closed container to minimize exposure to air and moisture.
Store KI away from strong oxidizing agents and acids to prevent chemical reactions.
Ammonium chloride (NH4Cl):
Preparation:
Ammonium chloride can be prepared by the reaction of ammonia (NH3) with hydrochloric acid (HCl).
The chemical reaction is as follows:
NH3 + HCl → NH4Cl
Properties:
Ammonium chloride is a white crystalline solid.
It is soluble in water and has a cooling, salty taste.
NH4Cl is an ionic compound with a melting point of 338°C (640°F).
It is a weak acid and can undergo reactions with bases.
Uses:
Ammonium chloride is used in cough medicines as an expectorant to help clear mucus from the respiratory tract.
It is used as a buffering agent in the pharmaceutical industry to maintain the pH of solutions.
NH4Cl is also used in the production of fertilizers, particularly for rice and wheat cultivation.
It is utilized in various industrial applications, such as electroplating, soldering flux, and metal recovery processes.
Storage:
Ammonium chloride should be stored in a cool, dry place, away from heat and direct sunlight.
Keep it in a tightly closed container to minimize exposure to air and moisture.
Store NH4Cl away from strong acids, bases, and oxidizing agents to prevent chemical reactions.