Page 258 - Pharmaceutics IV (02-06-01305)
P. 258
3/30/24
Foam !
When the aerosol valve is activated, the mixture
is expelled to the atmosphere, where the
propellant globules vaporize rapidly, leaving the
active ingredient in the form of a foam.
(o/w) (w/o)
If the propellant( oil phase) if the propellant is in the
represents the internal phase, external phase, the propellant
vaporizes and the emulsified
when the propellant
vaporizes, a foam is formed concentrate forms a finely
dispersed wet spray
Prof Alyaa Ramadan, ceutics, AU
23
Compressed Gas Systems
The use of gases that are insoluble in the product concentrate, as nitrogen,
will result in emission of a product in essentially the same form as it was
placed in the container.
An advantage of nitrogen as a propellant is its inert behavior toward other
formulative components and its protective influence on products subject to
oxidation. Also, nitrogen is an odorless and tasteless gas and thus does not
contribute adversely to the smell or taste of a product.
Other gases, such as carbon dioxide and nitrous oxide, which are slightly
soluble in the liquid phase of aerosol products, may be employed when their
expulsion with the product concentrate is desired to achieve spraying or
foaming.
Prof Alyaa Ramadan, ceutics, AU
24
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