Learning Objectives

• Importance and definition of displacement value
• Methods of manufacture of suppositories
• Evaluation tests for suppositories

Displacement Value

The volume of a suppository from a particular mold is uniform but its weight will vary because the densities of medicaments usually differ from the density of the base. Hence, it becomes necessary to calculate the displacement value of the base to be used for the particular medicament.

 

Definition: The number of parts of the medicament that displaces one part by weight of the base is known as the displacement value of that drug.

Calculation of Displacement Value of Medicament

Prepare and weigh 10 suppositories containing base alone = [A] g

Prepare and weigh 10 suppositories containing 40% of medicament = [B] g

Calculate the amount of base present in the medicated suppositories = [C] g

Calculate the amount of medicament present in the medicated suppositories = [D] g

Calculate the amount of base displaced by [D] g of medicament = [A – C] g

Displacement value of medicament 

Lubrication of the Mold

If the mold cavities are imperfect, poorly polished, or scratched, it becomes difficult to remove the suppositories without damaging their surfaces. So, lubrication of the molds is necessary. In case of greasy or oily base, water-soluble lubricants are required. For example, the following is the composition of lubricant solution for cocoa butter:

 

	Soft soap	10g
	Glycerol	10ml
	Alcohol (90%)	50ml

 

For water-soluble or water-miscible bases, oily lubricant may be used. For example, for glycero-gelatin base, liquid paraffin or arachis oil may be used as the lubricant.