Definition: Aerosol
Aerosols may be defined as disperse phase system in which very fine solid particles or liquid droplet get dispersed in the gases which act as continuous phase. These are also called pressurized dosage form.
Classification of aerosol
a. Space Sprays These are finally divided spray having particle size up to 50µ e.g. Insecticides, disinfectant.
b. Surface coat’s –
These are also spray but disperse particle are coarse with size up to 200µ
They produce a wet coat when sprayed on a surface e.g. Hair sprays, personal deodorant powder spray’s
c. Foam –
These are produced by rapid expansion of propellant through an emulsion. Hence, the product comes out in the form of foam or front.
E.g. Shaving cream & Vaginal product
OR
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 dissolved 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 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.
Formula of aerosol:
Aerosol formulations basically consist of propellant & the medicament to be propelled.
• Propellant
1) It develops a pressure in the container.
2) Compressed gases such as carbon dioxide or nitrogen & liquefied like methane or ethane used as propellant.
3) Compressed gases are not commonly used.
4) The medicament to be propelled may be solid or liquid.
5) It may be soluble in the propelled or insoluble.
6) The various additives such as solvent , antioxidant surface active agent, flavouring agent are also included in the formulation.
7) The propellant, medicament, additives are filled into an aerosol container.