Page 259 - Pharmaceutics IV (02-06-01305)

3/30/24

Difference between compressed and
liquified gas?

In case of In case of
liquified gas: compressed gas:

there is equilibrium between the there is drop in pressure during use
liquid phase and its vapour, and thus because the concentrate is expelled, the
the vapour pressure is constant after headspace increases and thus the gas
each actuation, as when propellant is
lost through actuation more vapour is expands and there is a decrease in
formed within the container and pressure after each actuation.
equilibrium is re-established.
Compressed gas propellant must have
high expansion volume,

i.e 1 ml compressed gas gives 200 ml
of vapour.

Which type is preferred iPnrofpAhlyaaa Rrammaadacn,uceeutiucst, AicUal aerosols?

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The effectiveness of a
pharmaceutical aerosol
depends on achieving the
proper combination of
formulation, container, and

valve assembly.

Prof Alyaa Ramadan, ceutics, AU

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