aerosols

1. contents:-
Definition, advantages and disadvantages
Classification of aerosols
Formulation of aerosols
Parts of an aerosol container
Packaging of aerosols

2.  Definiton-
 aerosols may be defined as dispersed phase system in which very fine
solid particles or liquid droplets gets dispersed in the gas which acts as
continuous phase . These are also called pressurised dosage form.
 Advantages-
 The medicament can be delivered directly to the affected area such as burnt skin and
wound. So it minimises the discomfort caused by mechanical or manual application.
 Absence of air prevents oxidation of the product.
 The hydrolysis of medicaments can be prevented
 The sterility of the products can be maintained
 The application of medicament is easier
 Disadvantages-
 Aerosols are costly preparations
 Some of the propellants are very toxic
 The cooling effect of highly volatile propellants may cause discomfort on injured skin
 Lot of difficulties are faced in aerosol formulation when the drug is not suitable

3. Classificaton of aerosol:-
 Aerosols may be classified as:
 1)Space sprays: these are finely divided sprays having
particle size upto 50micron,e.g. insecticides,
disinfectants , and room deodorizers
 2)Surface coats: these are also sprays but disperse
particles are coarse with sizes upto 200micron. They
produce a wet coat when sprayed on a surface e.g. hair
sprays, personal deodrants, powder sprays and topical
medicament sprays
 Foam: these are produced by rapid expansion of
propellantsthrough an emulsion. Hence, the product
comes out in the form of foam or froth, e.g. shaving
cream or vaginal product

4. Formulation of aerosols:
 An aerosol formulation basically consists of propellant and the medicaments to be
propelled
 Propellant – the propellant generally is regarded as the heart of the aerosol package. In
addition the necessary force to expel the product, the propellant must act as a solvent and
dileunt and has much to do with the determining the characteristics of the product as it
leaves the container. Various chemical compounds have been used as aerosol propellants.
compounds useful as propellants can be classified as-
 Liquefied gases- they have an advantage that the pressure within the container
remains constant, two types of liquefied gases are used:-
Chloroflurocarbons(CFC)-finds greater use since they are non-inflammable
e.g. propellant 11(trichloromonofluromethane), propellant12(dicholrodifluromethane).
 Hydrocarbons(HC)- they are advantageous since they are less expensive than any of the
fluorocarbons and generally are environment acceptable.
 Hydrochloroflurocarbons(HCFC)
 Hydroflurocarbons(HFC)
 Hydrocarbon ethers
 Compressed gasses
 Aerosol maybe of two types:-
 Two phase system- this is employed in cases where the product is a solid insoluble in the
propellant or it is solid or liquid which dissolve in it. In the first case the solid is suspended in the
propellant, so that aerosol system will have one liquid phase and one gaseous phase above it
 Three phase system- this system is employed in cases where the product is immiscible with
the propellant. The medicaments are dissolved in a liquid which does not mix with the liquefied
propellant.

5. Parts of an aerosol container:-
 An aerosol container can be divided into four parts-
1)Container- in pharmaceutical aerosol packaging, the containers are made out of
metal(such as tin plated steel, aluminum and stainless steel) glass and plastic. These
containers can withstand high pressure.
2)Valves- the valves should be such that it can be easily opened and closed. It should also
deliver the content in the desired form. So three types of valves are used these nowadays:
i)continuous spray valve
ii)metering valve
iii)foam valve
By using continuous spray valve, the medicament is expelled continuously as long as the
pressure is applied on the actuator.
But by using metering valve, only a definite quantity of the medicament is expelled when the
actuator is pressed.
If the contents of the aerosol are required to come out in the form of a ball of foam, a foam
valve is used is used in this case.
3)Actuator- actuator is fitted on the valve stem. It helps in the easy opening and closing of the
valve whenever it is required. There are various types of actuators which can produce
spray, fine mist or foam.
4)Dip tubes- the dip-tubes are made from polyethylene or polypropylene. Dip tube is used for
the following purpose :
i)it conveys the liquid from the bottom of the container to the valve at the top.
ii)It prevents the propellant to come out

6. Packaging of aerosols:-
 Cold filling process
Cool the product to -40F
Fill into the cooled container
Cool the propellant
Add the propellant to the product concentrate
 Pressure-fill process
fill the container with product concentrate
Place the valve in its position by compression
Now introduce the propellant via valve
Applications of aerosol packaging:-
1) They are used for spray bandages and for application of drugs meant for topical use.
2) They are used for spray administration of drugs into various body cavities.
3) The are for administration of drugs such as local anesthetics, local antiseptic, local
analgesics, and anti-inflammatory drugs.
4) They are used to spray cosmetics preparations such as perfumes.
5) They are used to spray disinfectants, deodorizers and air sanitizers.

7. Slide presentation by
Anurag Chanda
B.Pharm 5th Semester