2. 1. Definition
2. Classification
3. Components of
aerosol system
4. Containers
5. Formulation

3. • An Pharmaceutical aerosol is defined as
“pressurized containers, in which solid particles or
liquid droplets constitute the disperse phase and gas in
the continuous phase”.
• System that depends on the power of compressed or
liquefied gas to expel the content from container.

4. 1) Based on form : Solution, Suspension, Emulsion
2) Based on phases : Two phase - vapour + liquid
Three phase - vapour + aq
(water)+ propellant
3) Based on product delivered : Spray (particle size
50microns in diameter), Foam, &
Semi solid (200microns in diameter.)
4) Based on application : Topical, Inhalation, Intranasal

7.  These are compressed gases at 70 to 80 p.s.i.g
 They expel the contents of the container through
valves by applying force.
 They help in maintaining proper pressure in the
container & are they are considered as important
elements in the formulation.
 Propellants used may be in the form of –
Liquefied gases &
Compressed gases

8.  Liquefied Gases :
• They are widely used in the formulation of aerosols
because they are capable of dispensing active
ingredients in the form of fine mist.
• Liquefied propellants are actually gases which
exists as liquid under pressure.
• Whenever the product is dispensed from the
container, a part of liquid occupies the head space.
In this way the head space is always occupied by gas
which maintains the constant pressure and performance
of spray is also maintained.

9.  Liquefied gases are of 3 types:
a) Chlorofluorocarbons.
b) Hydro fluorocarbons.
c) Hydrocarbons.
a) Chlorofluorocarbons : 3 types –
i) Trichloromonofluoromethane (propellant 11)
ii) Dichlorodifluoromethane.
iii) Dichorotetrafluroethane.

10. b) Hydroflurocarbons :
• Due to several dis-advantages with CFCs, they have
been replaced by Hydro fluorocarbons (HFCs)
• Several propellants like Tetrafluoroethane ( 134a )
& Heptafluoropropane ( 227 ) have been developed
which are the substitutes of propellant 12
• These propellants have same properties as that of
propellant 12, except solubility characteristics.

11. c) Hydrocarbons :
 They are used to formulate Topical aerosols, due to
following reasons –
• They donot undergo hydrolysis, & hence they are
used in formulation of water based aerosols.
• As they are immiscible with water they are used in
formulation of 3 phase aerosol system.
• They are used in MDIs & topical administration.
• They have wide range of solubility, chemically
stable & low order of toxicity.

12.  Physical properties :
• Propellants (such as 11, 12, 114) are non-polar
compounds.
• They are miscible with non-polar solvents at desired
temp & have ability to dissolve many substances.
• They are immiscible with water, and hence to make
miscible with water, co-solvents such as ethanol can
be added.
 Chemical properties :
• They are Chemically inhert, non-inflammable, non-
toxic
• Propellant 11 undergoes hydrolysis, giving HCL,
hence it is not preferred in the formulation of
Aq.aerosol product.

13.  These are of 2 types :
a) Soluble C.gases ( CO2, N2O )
b) Insoluble gases ( Air, Nitrogen, Argon )
• Propellants like O2 & CO2 are used as compressed gases
& helps in dispensing the product in the form of mist,
foam or semi solid
• In the c.gas spray system, the liquid product is poured is
poured into container & is sealed
• The c.gas propellant is then filled under high pressure
into the container through the valve.
• Due to the high pressure, the liq.product is forcefully

14. • The C.gas propellant occupies only the head space,
Present above the liq.product in the container
• When the valve of aerosol can is opened the
liq.product,is pushed out through the nozzle.
• After the expulsion of the liq.product the amount of
gas in the head space of the can still remains same,
occupies more space thus reducing the pressure in the
container.
• The container is not completely filled with
liq.product, so as to provide enough head space for the
gas propellant, thereby avoiding any possible risk of
bursting of container.

16.  Filling Machines :

17. • Various types of materials are used in the
manufacture of aerosol containers.
• The containers used in the formulation of aerosols
should with stand high pressure i.e.,140 to 180 psig
and temperature of about 54.44 c.
 Types of materials used :
1. Metal
2. Glass

18. 1) Metal : Two types of metal containers are used -
a) Tin plated steel &
b) Aluminum

19. 2) Glass : Two types of glass containers are used -
a) Plastic coated glass &
b) Uncoated glass.

20. • The modern day aerosol valves are multifunctional i.e.
basic part of Aerosol containers as they deliver product in
desired form, from the container & help’s in preventing
the loss of product when the container is not in use.

21.  Components of Continuous spray valves -
a) Mounting cup
b) Valve body
c) Stem
d) Gasket
e) Spring
F ) Dip tube

22.  Some metering type of valves have been designed which
permit only a specified amount of product to come out .
 Such valves actually consist
of two valve's chambers both
of which are connected to
actuator.
 Valve contain extremely
small opening ( 0.018 to
0.030 inch )

24. • Formulation of Aerosols involves two components
namely –
a) Product concentrate
b) Propellants
Various type of systems are –
1) Solution system / Two phase system
2) Water based system / Three phase system
3) Suspension / Dispersion system
4) Foam system - a) Aq. Stable foams
b) Non-aq.stable foams

25. 1) Solution system :
 Propellant 12 is used generally in formulation of
this system, because it helps in producing very fine
particles.
 As A. ingredients are dissolved in propellants,
solvents are not required.
 The amount of propellant used in the system ranges
from 5% (used in production of foams) to 95% (used
in production of inhalation products)

26. 2) Water based system :
• Water is used to replace non-aq.solvents & ethanol
is used as a co-solvent to solubilize the propellant in
water & also helps in producing small particles.
• This system also utilizes Surfactants (0.5 – 2.0%) to
large extents, which helps in formation of
homogenous dispersion.
Ex : Oleic, Stearic, Palmitic & Lauric acids

27. 3) Suspension / Dispersion system :
• It consists of A. ingredients dispersed in propellant
& this system is used for oral inhalation purposes.
• Surfactants / suspending agents are also utilized to
decrease the rate of settling of dispersed
a.ingredients.
• After the formation of suspension system, some
particles show a tendency to aggregate due to
solubility, moisture or particle size growth.

28. • When large agglomerates are formed then it leads
to caking, & at higher temp. there is an increase in the
rate of Agglomeration, which leads to flocculation.
• These particles stick to the wall of the container,
leading to valve clogging resulting improper dosage &
the particles also damage the metal container.
• Agglomeration is avoided by controlling the
moisture content & in order to reduce agglomeration,
surfactants & lubricants are also added.
 Example of lubricants :
Isopropyl myristate & Mineral oil.

29. 4) Foam systems :
• This system consists of A.ingredient, aq & non-aq
vehicle, surfactant & propellant.
• These systems are dispensed in the form of
quick-breaking foams or stable foams.
• This type of system is preferred for those
ingredients, which cause irritation as well as when
aerosol is to be applied into limited area.
 Various type of foam systems are :
a) Aq.stable foams ; b) Non aq.stable foams
c) Quick breaking foams ; d) Thermal foams

30.  QUALITY CONTROL TESTS
Includes -
 1. Containers.
 2. Propellants.
 3. Valves, Actuator, Dip Tubes.
 4. Weight Checking.
 5. Leak Testing.
 6. Spray Testing.

31.  Tests for Valves, Actuators & Dip tubes :
 25 valves are selected which are placed on suitable
containers, containing Test sol. (i.e., Test sol. 1, 2, 3)
 To this container a button type actuator (0.020 inch
of orifice) is attached.
 The product in the container is allowed to attain a
temp. of 24-26 degree centigrade, & weight is
checked.
 A single delivery is completely dispensed by
pushing the valve at least for 2sec & the procedure is
repeated for 10times & after dispensing a single
delivery, the container is weighed.

32.  A. Flammability & Combustibility :
1. Flash point 2. Flash Projection
 B. Physicochemical Characteristics :
1. Moisture content 2. Identification of
Propellants
 C. Biological testing : 1. Therapeutic activity

34.  A dose can be removed with out contamination of
materials.
 Stability is enhanced for those substances adversely
affected by oxygen and or moisture.
 The medication can be delivered directly to the
affected area in a desired form, such as spray, steam,
quick breaking foam or stable foam.
 Irritation produced by the mechanical application of
topical medication is reduced or eliminated.
 Ease of convenience of application.

35.  Aerosols are capable of dispensing the product in various
forms, by which max. Therapeutic action can be achieved.
 MDIs are capable of delivering the req.amount of drug to
deep of the lungs.
 With the help of Metered valve aerosols, specified
amount of product can be dispensed.
 With the help of Special type Actuators we can deliver
the drug to specified sites.

36.  TheTheory & Practice Of Industrial Pharmacy” by
Leon Lachman, H.A.Liberman, Joseph Kanig, 3 rd
Edition,Varghese Pub., page no. 613-618.
 Remington’s “The Science & Practice Of
Pharmacy” 3 rd Edition,Volume-I, page no.1014-
1015.