1.3 Paste

Question 1

Define paste

Answer 1

A semi-solid dosage form that contains a large proportion of solids finely dispersed in fatty vehicles for external applications

Question 2

What are the properties of paste ?

Answer 2

-stiff
-remain in a place after application
-not suited for application to hairy parts of the body
-good adhesion on skin
-don’t melt at ordinary temperature

Question 3

Give 3 bases that are used for pastes

Answer 3

-hydrocarbon (oleaginous) bases
-water miscible (o/w emulsion) bases
-water soluble bases

Question 4

What are the differences between the preparation of paste and ointments ?

Answer 4

Pastes are prepared the same way as ointments, (mixing or the use of heat to soften the base to incorporating the solids) but pastes will be using levigating agent to render the powdered component smooth and a portion of the base would be used rather than liquid.

Question 5

What are the classifications of pastes based on the type of base used in formulation ?

Answer 5

-fatty pastes
-aqueous gel pastes
-hydrochloride pastes

Question 6

2 methods of paste preparation ?

Answer 6

-fusion
-fusion and trituration

Question 7

Describe the fusion method

Answer 7

1-any powder pass through under mesh no.180
2-melt all bases and wax with continuous stirring
3-then add powder form ingredient
4-continuous stirring
-ex: zinc and coal for paste
-uses: treatment for eczema

Question 8

Describe the fusion and trituration method

Answer 8

1-pass the powders through mesh no.180
2-melt the base
3-take powder in mortar and triturate with melted base
4-triturate until cool
-ex: compound zinc paste BP
-uses: treatment for eczema and for sun protection