aerosols

AerosolsDr. Basavaraj K. Nanjwade M. Pharm., Ph. D

Department of PharmaceuticsFaculty of Pharmacy

Omer Al-Mukhtar UniversityTobruk, Libya.

E-Mail: [email protected]

2014/06/14 1Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

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


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.


Advantages of Aerosols1. 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.


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.


Classification of Aerosols1. Space sprays: These are finely divided sprays having

particle size upto 50 . e.g. insecticides, disinfectants and room deodorizers.

2. Surface coats: These are also sprays but disperse particles are coarse with size upto 200 . 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.


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.


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.


Containers used for aerosols

• Aerosol container can be divided into four parts:

1.Container:2.Valves:3.Actuator:4.Dip tubes:


Aerosol container

2014/06/14 Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya. 10

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.


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.


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 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.2014/06/14 14Faculty of Pharmacy, Omer Al-Mukhtar University,

Tobruk, Libya.

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.


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 400F.

• The concentrate is generally cooled to below 00 in order to reduce loss of propellant during the filling operation.


• 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 1300F (540C) 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.


1. Cold-fill process

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 1300F (or 540C) 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.


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.


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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aerosols

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