pastes

2. PASTES
 Pastes are usually prepared by incorporating solids directly into a
congealed system by levigation with a proportion of base to form paste
like mass.
 Contains high percentage of insoluble solid (usually 50% or more) which
are finely dispersed into a suitable vehicle.
 Pastes adhere well to skin and are benefit in treatment of chronic
lesions.

3. Characteristics of Pastes
 Pastes are stiffer than other semisolid dosage forms such as ointments and
creams hence they remain stable at site of application.
 Because of high powder contents pastes are porous; hence, perspiration can
escape.
 They do not interfere with the non-infected areas of the skin.
 These are considerably less greasy when compared to ointments.
 They are mostly applied over moist lesions as they possess good adhesive
property towards the skin.
 Most of the pastes are unsuitable for treating scalp conditions because they
are difficult to remove from the hair.

4. Types of pastes
Based on the type of base used in formulation, pastes are classified as follows:
 Fatty Pastes
• These formulation consist of fatty or oleaginous bases.
Eg: Zinc oxide paste.
 Aqueous Gel Pastes
• These are prepared with water miscible bases.
Eg: Sodium hydroxymethyl cellulose paste, Titanium dioxide paste.
 Hydrocolloid Pastes
• These preparations consists of hydrocarbon bases.
Eg: Tooth paste, Zinc oxide gelatin paste.
Medicated Paste Non medicated paste

5. Formulation
Various types are bases used in preparation of pastes:
⇰ Hydrocarbon Bases
Soft paraffin and liquid paraffin are commonly used bases.
Name of the
preparation
Active ingredients Base Use
Compound Zinc
Paste B.P.
Zinc oxide Soft paraffin Eczema, Psoriasis.
Compound Zinc &
Salicylic acid Paste
B.P.
Zinc oxide &
Salicylic acid
Soft paraffin Eczema, Psoriasis.
Coal tar paste Coal tar Soft paraffin Eczema
Dithranol paste
compound
Dithranol Soft paraffin Ring worm
Aluminium paste
B.P.C.
Aluminium oxide Liquid paraffin Protectant

6. ⇰ Water miscible Base
Water miscible bases includes emulsifying ointments and
emulsifying wax used for the preparation of pastes.
Name of the preparation Base Use
Resorcinol & sulfur Paste
B.P.C.
Emulsifying ointment Treatment of Dandruff
Zinc & Coal tar Paste Emulsifying wax Eczema
Magnesium sulfate paste
B.P.C.
Magnesium sulfate-45%
Phenol in glycerol
Used to treat boils

7. ⇰ Water soluble Base
Water soluble bases are prepared from mixture of high and low
molecular weight polyethylene glycols.
Name of the preparation Base Use
Water soluble dental
pastes
Neomycin sulfate Sterilizing infected root
canal
Triamcinolone Dental paste
B.P.C.
Triamcinolone acetonide in
an adhesive paste(sodium
carboxy methyl cellulose,
pectin + gelatin)
Anti inflammatory

8. Additives used in paste

9. Ingredients used in toothpaste
Medicated toothpaste active
ingredients
Toxic toothpaste ingredients
Potassium citrate Triclosan
Potassium nitrate Sodium lauryl sulphate
Sodium mono fluorophosphate Artificial sweeteners
Triclosan Flouride
Strontium chloride Propylene glycol
Diethanol amine(DEA)

10. Methods of preparation
 Pastes are prepared by trituration and fusion methods.
 Trituration method is used when the base is liquid or semisolid.
 Fusion method is used when the base is semisolid/solid in nature.
⇰ Trituration method
Compound Zinc Paste is prepared by both fusion and trituration method.
Procedure:
 Zinc oxide and starch powder are passed through sieve No. 180.
 Soft paraffin is melted on a water bath.
 Required amount of powder is taken in a mortar, triturated with little melted base
until smooth and gradually rest of the base is added.

11. ⇰ Fusion method
Zinc and coal tar Paste B.P.C. is prepared by fusion method.
 Method 1
The components are melted in decreasing order of their melting point i.e., higher M.P.
the substance should be melted first.
The medicament is added slowly in the melted ingredients and stirred thoroughly until
the mass cools down.
 Method 2
All the components are taken in subdivided state and melted together.

12. Manufacturing
Manufacturing involves
 Weighing and mixing
 Filling tubes
 packing

13. Evaluation Parameters
 Evaluation of pastes are same as ointments

14. Liquid phase migration
Method

15. Tooth paste
 Mechanical strength
 Calcium hydroxide based on dental cement
Compressive strength is calculated in Mpa as below
C=
4𝑃
Π𝑑²
P - maximum load applied in Newton
d - diameter of specimen in mm