The displacement value measures a suppository’s volume in a molded cavity or mold. It is an important parameter in suppository formulation and manufacturing, as it helps ensure accurate dosing of the active ingredient. The displacement value is often expressed as a percentage and is calculated using the formula:

Here’s a step-by-step guide on how to calculate the displacement value:

1. Measure the Volume of the Mold Cavity:

Use an appropriate measuring device to determine the volume of the suppository mold or cavity. This can be done by filling the mold with a known quantity of liquid (e.g., water) and measuring the volume.

2. Prepare a Suppository:

Formulate and prepare a suppository using the desired base and active ingredients.

3. Measure the Volume of the Suppository:

After the suppository solidifies, measure its volume by carefully removing the suppository from the mold and placing it in a graduated cylinder or another volumetric container filled with water.

4. Calculate the Displacement Value:

Use the formula mentioned above to calculate the displacement value. Divide the volume of the suppository by the mold cavity volume and multiply by 100 to express the result as a percentage.

For example, if the volume of the suppository is 1.8 mL, and the volume of the mold cavity is 2.0 mL, the displacement value would be:

A displacement value close to 100% indicates that the suppository fits well into the mold, leaving little or no air gaps. This ensures accurate dosing of the active ingredient. If the displacement value is significantly less than 100%, the formulation or manufacturing process may require adjustments to achieve better conformity between the suppository and the mold.