Expectorants

Expectorants are medications or natural ingredients that help clear mucus from a person’s airways. They can be used for coughs that produce mucus, such as the common cold or flu. Expectorants aim to make coughing up mucus easier. They do not actually stop coughing. A productive cough should not be suppressed because it helps the body remove excess mucus, foreign particles, or microorganisms from the airways. Expectorants work by increasing the water content of secretions, which decreases their stickiness. This makes mucus easier to cough up.

Table of Contents

Classification of expectorants

Expectorants are classified according to their mechanism of action. They are of two types one is sedatives and another is stimulants.

Sedatives

They produce their effect through stimulation of gastric reflexes. Hence, they create some sort of gastric irritations. Drugs which are bitter like ipecac, senega, Indian squill and compounds like antimony potassium tartarate, ammonium chloride, sodium citrate and potassium iodide are some of the examples of sedative expectorants.

Stimulants

These agents bring out stimulation of the secretory cells of the respiratory tract directly or indirectly. More fluid is produced in the respiratory tract and sputum gets diluted. For example, terpenoid oils like eucalyptus, lemon, anise, and active constituents of oil like terpene hydrate and anethole.

Some of the inorganic compounds of recognisable expectorants activity are given below.

Potassium iodide

Molecular formula: KI

Molecular weight: 166

Preparation

There are two methods of preparation. In first method, it is prepared by the action of iodine on moist iron filing, which produces ferro-ferric iodide (FeI3.FeI2), it is then decomposed with potassium carbonate.

Fe + I2 — > FeI2,3FeI2 + I2 — > FeI2.FeI

FeI2.2FeI3 + 4K2CO3 — > 8KI + FeO.Fe2O3 + 4CO2

Ferro-ferric iodide (FeI3.FeI2) is filtered out and the filtrate is concentrated to obtain potassium iodide. It is then purified by recrystallisation.

In another method it is prepared by adding excess of iodine to the solution of potassium hydroxide.

6KOH + 3I2 — > 5KI + KIO3 + 3H2O

KIO3 + 3C — > KI + 3 CO2

Properties

Colourless transparent or opaque salt
Odourless
Saline bitter in taste
Salt is deliquescent in moist air
Soluble in water and organic solvents

Uses: It acts as a sedative type of expectorant because of iodide ions. The action is rapid and produces bronchial fluid which dilutes sputum. It is also used as a source of iodine and potassium. It is employed as stabilizer in the preparations of iodine solutions. Also used as the reagent in various reactions.

Assay

Potassium iodide is assayed by titrating with potassium iodate as oxidising agent. A known quantity is dissolved in water, acidified with hydrochloric acid and the contents titrated with standard potassium iodide solution using chloroform as an indicator solvent.

Storage: It is stored in well closed containers.

Ammonium chloride

Molecular formula: NH4Cl

Molecular weight: 53.5

Preparation

It is prepared by the interaction of ammonia gas to hydrochloric acid. The final solution is evaporated to dryness. The salt is purified by crystallization and sublimation by using 5% calcium phosphate.

NH3 + HCl — > NH4Cl

Properties

White and odourless
Crystalline or coarse powder
Cooling and saline taste
Slightly hygroscopic
Very soluble in water
Sparingly soluble on organic solvents

Uses

Ammonium chloride has three main pharmacological actions depending upon the dose.

It maintains acid-base equilibrium of body fluids. Also useful in deamination of amino acids. Dose for this action is 2g four times a day.
It produces diuretic effect due to utilization of ammonium cation in conversion into urea and in the process proton and chloride ions are produced. Continuous use may increase acidity of urine and metabolic acidosis is produced.
It also acts as mild expectorant and diaphoretic when administered in small doses. It is widely used in the cough preparations. Required dose for expectorant action is 0.3-0.5g per day.

Assay

Previously it was titrated by Volhard’s method based on precipitation titration. Now it is assayed by formal titration principle. In this method it is titrated with formaldehyde solution using phenolphthalein as an indicator.

Storage: It is stored in tightly closed containers.

Summary

Expectorants are medications or natural ingredients that help clear mucus from a person’s airways. They are particularly useful for alleviating congestion due to the common cold or flu. When someone has a productive or wet cough that produces mucus, expectorants come into play. These medications reduce the thickness of mucus and make secretions in the airways thinner. Expectorants are classified according to their mechanism of action. They are of two types one is sedatives (potassium iodide) and another is stimulants (ammonium chloride).