This document discusses aerosols, including their definition, advantages, disadvantages, classification, formulation, containers, packaging, and applications. It notes that aerosols are dispersions of fine particles or liquid droplets in a gas, and are also called pressurized dosage forms. Common propellants are mentioned, and it is explained that aerosol formulations can be two-phase or three-phase systems. Important uses of aerosols include topical and respiratory drug delivery.

1. Aerosols
Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D
Department of Pharmaceutics
Faculty of Pharmacy
Omer Al-Mukhtar University
Tobruk, Libya.
E-Mail: nanjwadebk@gmail.com
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Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.

2. Contents
• Definition
• Advantages and disadvantages of aerosols
• Classification of aerosols
• Formulation of Pharmaceutical aerosols
• Containers used for aerosols
• Packaging of aerosols
• Applications of Aerosol packaging
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3. Definition
• Aerosols may be defined as disperse phase system, in
which very fine solid particles or liquid droplets get
dispersed in the gas which acts as continuous phase.
• These are also called pressurized dosage form.
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4. Advantages of Aerosols
1. 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.
2. Absence of air prevents oxidation of the product.
3. The hydrolysis of medicaments can be prevented.
4. Drugs can be given by oral inhalation.
5. The sterility of the products can be maintained.
6. The application of medicament is easier.
7. A fine mist is easily formed for inhalation purpose.
8. Manual contact with medicaments can be avoided.
9. Drugs given by oral inhalation do not pass through G.I.T. Hence
its chances of decomposition are less.
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5. Disadvantages of Aerosols
1. Aerosols are costly preparations.
2. Some of the propellants are very toxic.
3. The cooling effect of highly volatile propellants may
cause discomfort on injured skin.
4. Lot of difficulties are faced in aerosol formulation
when the drug is not soluble in propellant.
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6. Classification of Aerosols
1. Space sprays: These are finely divided sprays having
particle size upto 50 µ. e.g. insecticides, disinfectants and
room deodorizers.
2. Surface coats: These are also sprays but disperse particles
are coarse with size upto 200 µ. They produce a wet coat
when sprayed on a surface. e.g. hair sprays, personal
deodorant, powder sprays and topical medicament sprays.
3. Foam: These are produced by rapid expansion of
propellants through an emulsion. Hence, the product
comes out in the form of a foam or froth. e.g. shaving
cream and vaginal product.
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7. Formulation of
Pharmaceutical aerosols
• An aerosol formulation basically consists of a propellant and the
medicaments to be propelled.
• Propellant: it develops a pressure in the container. Compressed gases such
as carbon dioxide or nitrogen and liquified gases like methane or ethane
can be used as propellants. Compressed gases are not commonly used.
These days propellants like trichloro-fluoro-methane, dichloro-difluoro-
methane, dichloro-tetrafluoro-ethane and difluoro-ethane are used in
pharmaceutical aerosols.
• The medicament to be propelled may be solid or liquid. It may be soluble
in the propellent or insoluble in it.
• The various additives such as solvents, antioxidants, surface, active agents
and flavouring agents are also included in the formulation.
• The propellants, medicaments and additives are filled into an aerosol
container.
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8. Formulation of
Pharmaceutical aerosols
• Aerosol system may be of two types:
1. Two phase system: Two phase system 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 solid is suspended in the propellant, so that
aerosol system will have one liquid phase and gaseous
phase is above it.
2. Three phase system: Three phase is employed in cases
where the product is immiscible with the propellant. The
medicaments are dissolved in liquid which does not mix
with the liquefied propellant.
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9. Containers used for
aerosols
• Aerosol container can be divided into four
parts:
1.Container:
2.Valves:
3.Actuator:
4.Dip tubes:
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10. Aerosol container
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11. 1. Container:
• In pharmaceutical aerosol packaging, the
containers are made from metal (such as tin
plated steel, aluminium and stainless steel)
glass and plastic.
• These containers can withstand high pressure.
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12. 2. Valves:
• The valves used 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 nowadays:
(i)Continuous spray valve
(ii)Metering valve
(iii)Foam valve
• By using continuous spray valve, the medicament is
expelled continuously as long as pressure is applied on the
actuator. But by using metering valve, only a definite
quantity of medicament is expelled when actuator is
pressed.
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13. 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.
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14. 4. Dip tubes:
• The dip tubes are made from polyethylene or polypropylene.
• Dip tube is used for the following purposes:
(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 without dispensing the
contents of the package.
• The dip tube should be extended almost to the bottom of the
container.
• In case the length of the dip tube is short, the contents of the
aerosol container will not come out of it.
• However, if the dip tube is touching the bottom of the
container, it will block the passage of liquid.
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15. Packaging of aerosols
• The aerosol products can be filled in two ways:
1. Cold-fill process.
2. Pressure-fill process.
• Depending on the nature of the product concentrate,
the aerosol can be filled by a cold filling or a pressure
filling process.
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16. 1. Cold-fill process
• This process is used to fill metered aerosol products
using a fluorocarbon propellant.
• By lowering the temperature of a propellant below its
boiling point, the propellant becomes liquid at
atmospheric pressure.
• The active ingredients or concentrate and propelant
are cooled to a low temperature of about -300
to 400
F.
• The concentrate is generally cooled to below 00
in
order to reduce loss of propellant during the filling
operation.
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17. • The chilled concentrate is poured into the chilled container
and propellant is added.
• Sufficient time is given for the propellant to partially vaporise,
in order to expel the air present in the container.
• The valve is fitted on to the container which is placed into a
water bath so that the contents are heated to 1300
F (540
C) in
order to check any leakage and strength of container.
• A dry ice-acetone bath is used to obtain the desired low
temperature for laboratory scale preparation whereas
refrigeration equipment is used for the large scale production
of aerosols.
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Tobruk, Libya.
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1. Cold-fill process

18. 2. Pressure-fill process
• This process is used for filling aerosols containing
hydrocarbon propellant.
• The product concentrate is placed into the container
and the valve is sealed.
• The propellant is forced through the valve under
pressure. After this the container is immersed in a
water bath at 1300
F (or 540
C) in order to check any
leakage and strength of the container.
• It is essential that the air present in the container must
be expelled before filling the contents into the aerosol
container.
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19. 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. They are used for administration of drugs such as local
anaesthetics, local antiseptic, local analgesics and anti-
inflammatory drugs.
4. They are used to spray cosmetic preparations such as
perfumes.
5. They are used to spray disinfectants, deodorizers and air
sanitizers.
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20. Application of Aerosols in
Pharmacy
1. The use of aerosols as a dosage form is particularly
important in the administration of drugs via the
respiratory system.
2. In addition to local effects, systemic effects may be
obtained if the drug is absorbed into the bloodstream
from the lungs.
3. Topical preparations are also well suited for
presentation as aerosols.
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Tobruk, Libya.
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21. THANK YOUE-mail: nanjwadebk@gmail.com
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Tobruk, Libya.