Glycerol: The Ingredient that Makes the Cough Syrups Liquid
Dr. Somedatta Ghosh (Pal)
Medical Writer (Medicomarketing)| Diabetology | Chemistry Expert | Skilled at Science Communication
Most of the medicines are found in the form of tablets and capsules. However, it is very well known that cough medications are formulated as liquids. They are called cough syrups.
According to consumer surveys, most people want cough medications in liquid form. During cough, we have a swollen throat associated with throat pain. It leads to painful swallowing. Liquids are easy to swallow in this phase. That’s the reason for the preference for cough syrup.
To obtain the liquid form, the medication's active ingredient is mixed with a liquid ingredient.
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Active Ingredient & Excipient
Active ingredients have pharmacologic actions on the body. Because of them, the medicines work. The ingredient other than the active ingredient is called excipient. Excipients play a supportive role in delivering the medicine. They are pharmacologically inactive.
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Glycerol: The Solvent of Cough Syrup
In cough syrup, commonly glycerol is used as one of the excipients. It is a viscous liquid by nature. When mixed with the active ingredient, it gives the cough syrup a thick liquid form. It plays other roles also in increasing the efficacy of cough syrups.
Honey and lemon are also used as other excipients to boost the flavour.
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Chemical Structure of Glycerol
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It ??is a colourless, odourless, viscous, sweet liquid. It has three hydrophilic alcoholic hydroxyl groups (-OH) and is thus very much soluble in water. Thus it can retain moisture. It is widely used in syrup, and skin lotions and prevents them from drying out.
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Mechanism of Action of Glycerol in Soothing Cough
Glycerol has no pharmacological action in the human body. Due to its physical and chemical properties, glycerol helps in soothing the problems related to cough and cold:
·?????? Lubricant: During cough, surfaces of the pharynx and tongue slide over each other during swallowing and talking. The friction irritates sensory nerves and the patient starts coughing.
·?????? Demulcent: A demulcent is a substance that forms a soothing film over a mucous membrane to relieve minor pain and inflammation of the membrane. Thus glycerol has a major effect in soothing our cough.
·?????? Sweetener: The sweet taste of glycerol makes the cough syrup tasty.
·?????? Humectant: Glycerol contains three hydrophilic alcoholic hydroxyl groups. Thus it can easily attract and hold water making the syrup soft, flexible, and creamy.
Glycerol is non-toxic to our digestive systems and does not create irritations to our skin and sensitive membranes. It only shows irritating properties at very high concentrations.
References:
1.???? Eccles R, Mallefet P. Soothing Properties of Glycerol in Cough Syrups for Acute Cough Due to Common Cold. Pharmacy (Basel). 2017 Jan 20;5(1):4.
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