Cough Syrup | Formulation and Manufacturing Considerations

Cough syrup is a liquid oral dosage form that is used for relieving cough. Syrups are common over-the-counter (OTC) medicaments. Syrup is a sweet liquid with a thicker consistency that is commonly used as a flavoring, sweetener, or as vehicle for the administration of medicaments. In this article, I will talk about the formulation as well as the manufacturing consideration of syrups.

Cough Syrup

Syrups are oral liquid formulations in which the concentrated solution of sucrose or any other sugar in the water is used as a vehicle.

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The sugar concentration in the syrup should be 66.7% w/w.

The syrups are classified into two types;

1) Simple Syrups

Generally, simple syrups contain flavored substances that are also very pleasant but it does not contain any medicaments. Simple syrups are also used as a medium for other liquid oral formulations.

2) Medicated Syrups

The medicated syrups contain the medicinal substance in the vehicle along with some other ingredients which are responsible for formulating a syrup with the desired consistency.

Advantages of Syrups

1) The bitter taste of some medicaments can be minimized because the syrups are sweet.

2) Syrups also prevent oxidation as well as decomposition of many drugs as it consists of various oxidative agents.

3) Syrups are the most acceptable formulations, especially for children.

Disadvantages of Syrups

1) If syrups are taken for a longer period then they can cause dental decay.

2) For diabetic patients syrups are not preferred.

Syrups are generally prepared by dissolving either sugar or other sweeteners like corn syrup or honey in the water, and then their mixture is heated to make a thick consistency. There are various sources through which the syrups are formulated that include maple trees, corn, and sugar cane.

Liquid orals are mainly prepared by mixing the drugs in solvents with required additives.

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Additives and Components of Additives

Preservatives

For getting protection from microorganisms preservatives may be used to preserve the liquid orals (syrups).

The selection of preservatives depends on the study of microbiological guidelines.

Generally, for achieving the desired antimicrobial effects a combination of two or more preservatives is required.

There are the following types of sources through which the micro-organisms can enter into the liquid orals.

1) Raw materials such as solutes and solvents

2) Containers

3) Equipment

4) The manufacturing environments

5) Manufacturers or operators

6) Packaging materials.

Examples of preservatives

a) Acidic - Benzoic acid and its salts (0.1-0.3), Boric acid and its salts (0.5-1.0), Phenol (0.2-0.5), Chlorocresol (0.05-0.1)

b) Neutral - Nitromersol (0.001-0.1), Benzyl alcohol (1.0), 0-phenylethylethyl alcohol (0.2-1.0), Chlorbutanol (0.5)

c) Quaternary ammonium compound - Chloride (0.004-0.02), Benzalkonium Cetylpyridinium chloride (0.01-0.02)

A good preservative can retain its antimicrobial activity for the shelf life of the product.

With the help of microbiological evaluation, the characteristics of preservatives can be demonstrated.

Some specific organisms that are recognized as unacceptable for oral liquids such as Escherichia coli, Salmonella species, Pseudomonas species as well as proteolytic species of clostridium and candida albicans.

Sweetening Agents

Sweetening agents are one of the most important for liquid oral dosage forms, especially for syrups. They consist of a large portion of solid content in the dosage forms which required them.

Examples of sweetening agents

Some common examples are liquid glucose, sucrose, aspartame, and saccharin.

1) Sucrose is soluble in an aqueous medium and the solution which is prepared consists of 85 % sucrose in the medium.

At a pH range of 4 to 8, it is physically as well as chemically stable.

Sucrose is used in the conjugation with glycerine and sorbitol which minimizes the tendency of sucrose to crystallize.

2) Liquid glucose is a very viscous substance that imparts sweetness into the liquid orals.

3) Saccharin is also used as a sweetener in syrup preparations. It is almost 250 to 500 times sweeter than sugar

4) Aspartame is more sweeter than sucrose.

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Viscosity Controlling Agent

Sometimes it is required to increase the viscosity of syrups either to adjust for palatability or to improve the pourability.

For achieving the desired viscosity there are increasing the sugar concentration or adding viscosity-controlling agents like cellulose derivatives that are methyl cellulose and polyvinyl pyrrolidone.

Buffers

While storing the liquid oral dosage formulations there are following things that may occur such as interactions with container components, degradation of the product, and dissolution of gases and vapors that can cause changes in their pH level. It can be prevented by the addition of buffers.

A suitable buffer system should have an appropriate capacity to maintain the pH level of the formulations.

The buffer system should also affect the solubility as well as the stability properties of the syrups.

Buffer can also act adversely as a general acid or base catalyst and may cause the degradation of medicaments.

Hence, it is very important to study the effects of buffer before selecting it for syrups or liquid oral dosage forms.

Examples 

Acetates, Citrates, Phosphates, and glutamates.

Antioxidants

Many drugs may undergo oxidative degradation in the solution.

Loss of electrons from a compound that may lead to a change in molecules' oxidation state is known as oxidation.

Sometimes the packaging may also lead to the oxidation of drugs in the solution so there are more oxidants used to maintain the stability of drug products.

Examples

Butylated hydroxytoluene, Butylated hydroxyanisole, and Ascorbic acid.

Flavors

To mask the bitter and unpleasant taste of the liquid orals a combination of flavoring agents is generally required which masks these taste sensations very efficiently.

The flavoring agents generally provide their flavor and odor to the formulations and also give a mild anesthetic effect.

   

Example

Menthol and Chloroform

Chloroform is also used as a sensitizing agent.

Solvents

A pharmaceutical solvent, an emulsion, a suspension, or a solution in liquid oral dosage forms can be a vehicle.

The vehicle properties depend upon the type of solvent used as well as the route of administration for the formulation.

Examples

Water, Alcohol, Propylene Glycol, Glycerin, and Artificial sweeteners.

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Hence, syrups are often used as a vehicle for the administration of medicaments, especially for children or those patients who have difficulty swallowing either pills or tablets as well as capsules. Medicaments like cough syrup and pain relievers are manufactured as syrups for this reason. Hope, you have liked the article on cough syrup. If you have any points please ask in a comment.

FAQ

Ques 1- What is the formulation of pharmaceutical syrup?

Ans- The formulation of pharmaceutical syrup generally includes components like active ingredients, excipients (such as sweeteners, flavoring agents, coloring agents, preservatives, thickening agents, and water), Solubilizers, and antioxidants.

Ques 2- What is the formulation of simple syrup?

Ans- 1) Selection of Vehicle.

2) Now add the weighed drug into the vehicle.

3) Now mixed with the help of a propeller.

4) Now add adjuvants such as sweetening agents, coloring agents, flavoring agents, and stabilizers.

5) Then, properly mix the mixture.

6) Finally, filter the mixture, pour it into the bottle, and label it./