Pharmaceutical emulsion part I

 

Disclaimer

 

Hey readers, this is Sarang More,  a former pharmacy student. This is blog about pharmaceutical emulsion. Yes!  Another important topic in pharmacy.  It had happened due to endless dedication of my professors and Principal sir of my college. I would thank Principal of my college Mr. Jiddewar sir for giving me this opportunity. I would also like to pay my respect to my parents, I would like to thank especially Dr. R. R. Sangpal sir, Mr. Nemade sir for their guidance. I would like to thank Mr.Akshay Kasambe sir, Mrs. Kalyani Pochchhi ma’am ,Mr. Shrikanth Kale sir, and Mrs Lad ma’am for encouraging me.

Thank you.   Thank you.  Thank you.

 Part I

An emulsion is a mixture of two immiscible phases, where one phase is dispersed into another.

An emulsion can be defined as biphasic system consisting of two immiscible system, one of which is finely and uniformly dispersed as globules throughout the second phase.

Alternatively it can also be defined as biphasic liquid dosage form of medicaments in which two immiscible liquid are mixed together to form a uniform mixture.

The liquid which is converted into minute globules is known as 'dispersed phase' and the liquid in which the globules are dispersed are known as 'continuous phase'.

Chemically no such liquid remains dispersed into another liquid for a long time so a emulsifying agent is added into it.

The emulsion primarily contain oil and water, but a advance emulsion not only contain oil and water, it may also contain some solid particles and gases.

Since the emulsion are thermodynamically unstable so an emulsifying agent is added into it to enhance its stability. The fundamental property of any emulsifying agent is to create a interfacial layer on the surface of dispersed phase.

An emulsion is an unstable system due to unfavourable contact between oil and water phases, but in some advance cases they can be make stable by using proper techniques by maintaining adequate particle size of dispersed phase and interfacial film which surrounds the drop.

Without adding any surface active agent is won’t be stable for particularly long period. If we didn’t add any surfactant the emulsion will start to separate in different layers depending on their densities.

The individual density and viscosity can’t be considered for making an emulsion, rather than the density of final product is important. So, depending upon the density of emulsion it would be categorized into lotions (low viscosity) and creams (high viscosity) .

The particle size ranges from 0.1-100um in dispersed phase often called as normal stable emulsion.

They cover the wavelength of normal visible light and hence emulsion tends to appear cloudy and pale blue.

The globule size in emulsion varies from 0.25- 25um diameter. Emulsion having large globule size are called as coarse emulsion while those having globule of 5um are considered as fine emulsion. The emulsion having globules size as small as 10 nm are known as microemulsion.

In spite emulsion of 20- 100um can be prepared are translucent and are quite stable thermodynamically which are known as nano emulsion ar ultra fine emulsion.

v  Types of emulsion:-

 

1.      Oil in water emulsion:-

An o/w emulsion is emulsion in which oil is existing as dispersed phase and water exists as continuous phase.

It is used for oral administration or as a vehicle for oil soluble drugs.

They are non greasy and are easily removable from skin surface and clothes.

They are also a good conductor of electricity

2. Water in oil emulsion :-

The water in oil type of emulsion is which the continuous phase is oil and dispersed phase is a water.

The water in oil emulsion contains three substances a solvent, a surfactant and water.

It is quite unstable but stability can be achieved by using natural surfactant like resins and asphatenes.

Fingas and Fieldhouse had revealed that water in oil emulsion can be classified into four categories-

a)      Stable emulsion – Brown in color and contains 80% of water.

 

b)      Metostable emulsion – It is brownish black in color.

c)       Unstable emulsion – separate in two states rapidly.

d)      Entrained emulsion – They are black in color and contains 40% water.



1.       Multiple emulsion:-

Multiple emulsion are complex system.

They are considered as emulsion of emulsion.

 They are more complex and contain very small droplets and suspended in larger droplets and that are also disperse in continuous phase.

They have limitations due to their complex structure and thermodynamics.

4.      Micro emulsion:-

These are system consisting of water, oil and surfactant which constitute single optically isotropic and thermodynamically stable liquid solution.

There are two types of micro emulsion – O/ W and W/O.

To prepare water in oil type of microemulsion, first create water in oil emulsion with anionic and cationic surfactant.

It is triturated with another co – surfactant and emulsion is passed through gel phase.

To prepare O/W emulsion start with O/W emulsion with low hydrophile lipophyile number

Add aqueous solution of high HLB number surfactant with gel and constant stirring. 

·        Classification of emulsion :-

 

A] Classification of emulsion accordance to the type of emulsifying agent used in preparation of an emulsion:-

 

(1) Emulsion containing natural gums

Eg – gum Acacia, gum tragacanth and mucilage of Irish moss

 

(2) Emulsion containing gum substitute:-

Eg – cellulose and it’s derivatives and salt of alginic acid.

 

(3) Emulsion containing various soaps

 

(4) Emulsion containing Saponins

 

(5) Emulsion containing starch

 

(6) Emulsion containing natural waxes

Eg – wool fat and beeswax

 

(7) Emulsion containing synthetic waxes

Eg – emulsifying wax and cetomacrogol emulsifying wax.

 

(8) Emulsion containing other emulsifying agent such as pectin, egg yolk, gelatin and lecithins.

 

B] classification of emulsion in accordance to their mode of administration:-

 

(1)    Emulsion for oral administration:-

These are usually O/w type of emulsion and are used to administer oils having medicinal value. Eg – Castor oil, olive oil

 

(2)    Emulsion for external use:-

These may either O/w or w/O type of emulsion

 

(3)     Emulsion for parenteral use:-

These are used to administer water soluble vitamin like A, D , E, K and oil soluble sex hormone, because their absorption is very rapid through these route.

 

(4)     Emulsion for rectal use:-

These are used in the form of enemas for evacuation of bowel. Starch mucilage is generally used in preparation of bowel.

 

Ø  Advantages of emulsion:-

1.       Medicine having an unpleasant taste and odour can be made palatable for oral administration in the form of emulsion. Eg – Castor oil and cod liver oil.

2.       Emulsion provides protection against drugs which are prone to oxidation and hydrolysis.

3.       Various external preparation like cream, ointment, and foam aerosols are formulated using emulsion.

4.       The sterile stable intravenous emulsion containing fats, carbohydrates, vitamin can be administer to patients who are unable to take them orally.

5.       They improve absorption of oiks when taken internally

6.       Nowadays a radio opaque emulsion are used as diagnostic agent in X ray examination.

 

Ø  Disadvantages of emulsion:-

1.       It cannot stand for long period of time, as it is unstable thermodynamically.

2.       There are lots of precautions regarding storage of emulsion.

3.       It bends towards expensive side in terms of manufacturing.

 

 

 

Ø  Ideal properties:-

1.       It should consist of uniform dispersion of fine and mono size droplet of internal phase, which should not aggregate and if they do, must not coalesce to form large droplet

2.       The internal droplet should not cream up and down and if they do, the cream layer should re dispersible.

3.       Without phase inversion, it should remain in its original state.

4.       It should not regarded by microbes on storage.

5.       It should be stable at various temperatures.

6.       It should not rancid or degraded due to oxidation

The second part will be released soon.... Please comment and share it to your friends and colleagues.