PASTES – PHARMACEUTICS II (Dispensing Pharmacy) D. Pharm 2nd year PDF Notes



Pastes are semi-solid preparations
intended for external application to the skin. The pastes are generally very
thick and stiff. They do not melt at ordinary temperature and thus form a
protective coating over the area where they are applied. They are used mainly
as antiseptic protective or soothing dressings which are often spread on lint
before being applied.


Bases used for pastes:

The following types of bases are used
for the preparation of pastes:

Hydrocarbon bases:
Soft paraffin and
liquid paraffin are commonly used bases for the preparation    of pastes.


Water miscible bases:
ointment is used as a water miscible base for the preparation of pastes.
Glycerine is also used as water miscible base for the preparation of pastes.


Water soluble bases:
combination of high and low molecular weight polyethylene glycols are mixed
together to get product of desired consistency which soften or melt when
applied to the skin. Ex: macrogol base.


Method of preparation of pastes:

Pastes are prepared by trifurcations
and fusion methods just like ointments. The trituration method is used only in
those cases where the base is liquid or semi-solid. The fusion method is used
when the base is semi solid or solid in nature.


Storage of pastes:

The pastes should be stored in a well
closed container and in a cool place so as to prevent evaporation of moisture
present in the paste. Pastes should be stored and supplied in containers made
up of materials which do not allow absorption or diffusion of the contents.


Differentiation between pastes and




1. They contain large amount of
finely powdered solids such as starch, zinc oxide, calcium carbonate etc.

2. They are very thick and stiff.

3. They are less greasy.

4. They are generally applied with a
spatula or spread on lint.

5. They form a protective coating to
the area where it is applied.

6. Paste contains large amount of
powder which is porous in nature, hence perspiration can escape.

7. They are less macerating than

1. They contain medicaments which
are generally dissolved /suspended/emulsified in the base.

2. They are soft semi solid

3. They are more greasy.

4. They are simply applied on the


5. They are used as protective or
emollient for    the skin.

6. They are used for the protection
of lesions.


7. They are more macerating in

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