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Emulsion Formulation
Drugs that are very unpleasant in taste and odor can be formulated more palatable for oral administration in the form of an emulsion. Emulsions also protect the drugs from oxidation as well as hydrolysis.Read more - Liquid Orals
Emulsion formulation is a biphasic formulation that contains two immiscible liquids that is one is a dispersed phase (particle size 0.1 to 100 μm), and another is the continuous phase. The disperse phase contains small droplets which distributed uniformly into another liquid that is a continuous phase by the use of an emulsifying agent.
Emulsifiers or emulgents are the agents that are used to stabilize the emulsion.
2) Emulsions provide sustained-release medication.
3) Emulsions also mask the unpleasant taste.
4) Emulsions are generally odorless & cost-effective.
2) Sometimes emulsions may lead to creaming and cracking.
3) Packing, handling as well as storage is also very difficult in the case of emulsion preparations.
4) Emulsions have a shorter Shelf life and are also thermodynamically unstable.
Emulsion formulation is a biphasic formulation that contains two immiscible liquids that is one is a dispersed phase (particle size 0.1 to 100 μm), and another is the continuous phase. The disperse phase contains small droplets which distributed uniformly into another liquid that is a continuous phase by the use of an emulsifying agent.
Emulsifiers or emulgents are the agents that are used to stabilize the emulsion.
Advantages of Emulsion
1) Emulsions are generally inert and also chemically non-reactive.2) Emulsions provide sustained-release medication.
3) Emulsions also mask the unpleasant taste.
4) Emulsions are generally odorless & cost-effective.
Disadvantages of Emulsion
1) Emulsion formulations may lead to phase inversion.2) Sometimes emulsions may lead to creaming and cracking.
3) Packing, handling as well as storage is also very difficult in the case of emulsion preparations.
4) Emulsions have a shorter Shelf life and are also thermodynamically unstable.
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1) Oil-in-Water (O/W) Emulsion
2) Water-in-Oil (W/O) Emulsion
3) Multiple or Double Emulsion
4) Microemulsions
The oil-in-water emulsions are also called aqueous emulsions.
These types of emulsions are mainly preferred for oral use.
The oil-in-water types of emulsion are generally used to prepare lotions, liniments, and creams because of their non-greasy property, and also very easily removed from the body.
Example - Milk (In this liquid fat globules are dispersed in the water)
The water-in-oil emulsions are also known as oil emulsions.
The water-in-oil emulsions are very good for sensitive or dry skin treatments as it is greasy.
Multiple emulsions are of two types;
The droplets of one liquid are dispersed in the droplets of another liquid that's why they are called multiple emulsion that is further dispersed into the dispersion medium.
Multiple emulsions or double emulsions are formulated for the prolonged release of the medicaments.
The multiple emulsion has a complex structure. They are widely used to increase bioavailability, and for controlled as well as targeted delivery of medicaments.
If compared with the conventional emulsion, the microemulsion is thermodynamically stable.
Microemulsions are formulated by dispersing oil in an aqueous solution and then a co-surfactant is added to the formulation.
The microemulsion acts as a carrier of drugs for oral, topical as well as parenteral administration.
Step 1- One part of the gum is triturated with four parts of oil into a dry mortar.
Step 2- Then add two parts of water all at once.
Step 3- Triturate the mixture continuously until the "cracking" sound is produced.
Step 4- At this point, the primary emulsion will be creamy white.
Step 5- Then add more amount of water into the primary emulsion.
Step 6- If there are any solid substances then added as a solution into the primary emulsion.
Step 7- Oil-soluble substances in a small amount can be added directly into the primary emulsion.
Step 8- To avoid breaking of emulsion any substance like alcohol may be added at the end of the process.
Step 9- Now, transfer the primary emulsion into a calibrated vessel.
Step 10- Now, make up the final volume with the water.
Step 2- During the process of trituration slowly add four parts of oil.
Step 3- To form the primary emulsion triturate it continuously.
Step 4- Add other ingredients if required.
Step 5- Transfer the primary emulsion to the graduated cylinder.
Step 6- Now make up the final volume with water.
Step 2- Then two parts of oil are added.
Step 3- Then after capping shake the mixture thoroughly.
Step 4- Add the water to the mixture and the volume of water should be equal to that of oil.
Step 5- Again shake the mixture vigorously until the primary emulsion is formed.
Step 6- Finally, dilute the mixture with the required volume of water.
During the shelf life of emulsion bacterial growth should not occur so the emulsion formulation should be chemically stable.
The stability of emulsions may either be reversible or irreversible and can be shown in the following ways;
There are the following reasons why cracking me occur;
The close location of droplets may also enhance the droplet coalescence if interracial film's mechanical properties are compromised.
Creaming can be re-dispersed due to the shaking or stirring and got again a homogeneous solution so it is a temporary phase.
The phase inversion may take place due to the following reasons;
The emulsion should be stored in a cool place and also emulsifying agent should be used in a required concentration.
I hope that you liked the article on emulsion formulation. If you have not gotten any points then feel free to ask in the comment.
Classification of Emulsions
The classification of emulsions is as follows;1) Oil-in-Water (O/W) Emulsion
2) Water-in-Oil (W/O) Emulsion
3) Multiple or Double Emulsion
4) Microemulsions
1) Oil-in-Water (O/W) Emulsion
In this type of emulsion, the disperse phase is oil and the continuous phase is water.The oil-in-water emulsions are also called aqueous emulsions.
These types of emulsions are mainly preferred for oral use.
The oil-in-water types of emulsion are generally used to prepare lotions, liniments, and creams because of their non-greasy property, and also very easily removed from the body.
Example - Milk (In this liquid fat globules are dispersed in the water)
2) Water-in-Oil (W/O) Emulsion
In this type of emulsion, the disperse phase is water and the continuous phase is oil.The water-in-oil emulsions are also known as oil emulsions.
The water-in-oil emulsions are very good for sensitive or dry skin treatments as it is greasy.
3) Multiple Emulsion or Double Emulsion
Multiple emulsion is also known as emulsion-within-emulsion.Multiple emulsions are of two types;
a) Oil-in-Water-in-Oil (O/W/O) type
In this type of emulsion, the oil-in-water (o/w) Emulsion is dispersed in another oil phase.b) Water-in-Oil-in-Water (W/O/W) type
In this type of emulsion, the water-in-oil (w/o) Emulsion is dispersed in another aqueous phase.The droplets of one liquid are dispersed in the droplets of another liquid that's why they are called multiple emulsion that is further dispersed into the dispersion medium.
Multiple emulsions or double emulsions are formulated for the prolonged release of the medicaments.
The multiple emulsion has a complex structure. They are widely used to increase bioavailability, and for controlled as well as targeted delivery of medicaments.
4) Microemulsion
Microemulsions are clear, transparent emulsion which contains globules that are less than 0.1 µm in diameter.If compared with the conventional emulsion, the microemulsion is thermodynamically stable.
Microemulsions are formulated by dispersing oil in an aqueous solution and then a co-surfactant is added to the formulation.
The microemulsion acts as a carrier of drugs for oral, topical as well as parenteral administration.
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A good emulsifying agent is non-toxic, colorless, odorless, and tasteless. At low concentrations, they can produce stable emulsions.
Emulsifiers generally enhance the mixture's kinetic stability.
Emulsifiers generally prevent coalescence and reduce creaming.
Examples - Surfactants, Sodium phosphate, and sodium stearyl lactylate, Acacia, Tragacanth, Agar, Gelatin, Bentonite, Magnesium Hydroxide.
Example - chloroform (0.25%), phenylmercuric nitrate (0.004- 0.01%), Chlorocresol (0.1%), cetrimide (0.002-0.01%), methyl paraben and propyl paraben (0.1-0.2%), chloroform (0.25%).
Examples - Propyl gallate, ascorbic acid, tocopherol, and gallic acid.
2) Staining test (Dye solubility test)
3) Conductivity measurement
4) Fluorescence test
Formulation of Emulsions
1. Emulsifying Agent
Emulsifying agents are substances that are used to stabilize the emulsion. These are also known as emulsifiers or emulgents.A good emulsifying agent is non-toxic, colorless, odorless, and tasteless. At low concentrations, they can produce stable emulsions.
Emulsifiers generally enhance the mixture's kinetic stability.
Emulsifiers generally prevent coalescence and reduce creaming.
Examples - Surfactants, Sodium phosphate, and sodium stearyl lactylate, Acacia, Tragacanth, Agar, Gelatin, Bentonite, Magnesium Hydroxide.
2. Preservatives
The preservatives are added to the emulsion to inhibit the growth of fungi, moulds, and bacteria that can cause unpleasant taste, odor, and discoloration of the emulsion.Example - chloroform (0.25%), phenylmercuric nitrate (0.004- 0.01%), Chlorocresol (0.1%), cetrimide (0.002-0.01%), methyl paraben and propyl paraben (0.1-0.2%), chloroform (0.25%).
3. Antioxidants
The antioxidants are added to avoid the oxidation that occurs either by oxidation or by enzymes produced by the microorganism.Examples - Propyl gallate, ascorbic acid, tocopherol, and gallic acid.
4. Coloring agents, Sweetening agents, and Flavouring agents
These are also added into the formulation of emulsion to enhance the aesthetic appearance of the emulsion as well as to enhance the acceptability of the patients.Read more - Suspension Meaning in Hindi
Tests for Identification of Emulsion Type
1) Dilution test (Miscibility test)2) Staining test (Dye solubility test)
3) Conductivity measurement
4) Fluorescence test
Preparation of Emulsions
The methods used for the preparation of emulsions are divided into two categories.1) Trituration Method
This method contains the dry gum method as well as the wet gum method.a) Dry Gum Method
There are following steps are used in the preparation of emulsion through the dry gum method;Step 1- One part of the gum is triturated with four parts of oil into a dry mortar.
Step 2- Then add two parts of water all at once.
Step 3- Triturate the mixture continuously until the "cracking" sound is produced.
Step 4- At this point, the primary emulsion will be creamy white.
Step 5- Then add more amount of water into the primary emulsion.
Step 6- If there are any solid substances then added as a solution into the primary emulsion.
Step 7- Oil-soluble substances in a small amount can be added directly into the primary emulsion.
Step 8- To avoid breaking of emulsion any substance like alcohol may be added at the end of the process.
Step 9- Now, transfer the primary emulsion into a calibrated vessel.
Step 10- Now, make up the final volume with the water.
b) Wet Gum Method
Step 1- To form mucilage one part of the gum is triturated with two parts of water.Step 2- During the process of trituration slowly add four parts of oil.
Step 3- To form the primary emulsion triturate it continuously.
Step 4- Add other ingredients if required.
Step 5- Transfer the primary emulsion to the graduated cylinder.
Step 6- Now make up the final volume with water.
2) Bottle Method
Step 1- In a bottle, one part of gum or powdered acacia is placed.Step 2- Then two parts of oil are added.
Step 3- Then after capping shake the mixture thoroughly.
Step 4- Add the water to the mixture and the volume of water should be equal to that of oil.
Step 5- Again shake the mixture vigorously until the primary emulsion is formed.
Step 6- Finally, dilute the mixture with the required volume of water.
Stability of Emulsion
The emulsion formulation may be stable as after its preparation it remains in the same condition. While storing the emulsion formulation the dispersed globules should be uniformly distributed throughout the dispersion medium so that it remains in a stable form.During the shelf life of emulsion bacterial growth should not occur so the emulsion formulation should be chemically stable.
The stability of emulsions may either be reversible or irreversible and can be shown in the following ways;
Cracking
The separation of two layers of the dispersed phase and continuous phase because of the coalescence of dispersed phase globules that are difficult to redisperse on shaking is called cracking.There are the following reasons why cracking me occur;
- The addition of a different type of emulsifying agent
- Due to the precipitation of emulsifying agent
- Due to the addition of a general solvent
- Due to the micro-organisms
- Due to changes in temperature
- Due to the creaming formation
Flocculation
The shaking will redisperse the droplets from a homogeneous formulation so flocculation may stabilize the formulation.The close location of droplets may also enhance the droplet coalescence if interracial film's mechanical properties are compromised.
Creaming
At the surface of the emulsion a thick layer is formed due to the upward movement of dispersed globules is called creaming.Creaming can be re-dispersed due to the shaking or stirring and got again a homogeneous solution so it is a temporary phase.
Phase Inversion
The change in the oil-in-water type of emulsion to the water-in-oil type of emulsion means a change from one form to another form is called phase inversion.The phase inversion may take place due to the following reasons;
- By changing the ratio of phase volume
- By electrolyte addition
- By chance in temperature
- Due to the change the emulsifying agent
The emulsion should be stored in a cool place and also emulsifying agent should be used in a required concentration.
I hope that you liked the article on emulsion formulation. If you have not gotten any points then feel free to ask in the comment.
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