Drug particle size The particle size of the drug is an important parameter for suspension suppositories. Increases dissolution of the dispersed particles the smaller the particle size the higher the dissolution rate. To prevent unwanted sedimentation during or after preparation, the drug should be incorporated in the base as fine (median size 125 ym to 180 (um) or very fine (median size leqslant 125 (m) powder. Displacement value A drug property which should be considered during the formulation of suspension suppositories, where the drug is dispersed in the molten base, is the displacement value The displacement value is the mass of drug that displaces 1 g of base, and it allows calculation of the required amount of base in the suppository formulation. Displacement value: The quantity of drug which displace one part of the base. Displacement value-Suppository B= Indicate Base; M indicates MedicamentDrug; a=amount of pure bases suppository (without medicament/drug); d-amount of medicament/drug; comount of base after medicament is incorporated

In the formulation of suspension suppositories, understanding both the particle size of the drug and the displacement value is crucial for ensuring proper dissolution and stability.<br /><br />### Particle Size<br /><br />1. **Importance**: The particle size of a drug affects its dissolution rate. Smaller particles have a larger surface area relative to their volume, which increases the rate at which they dissolve in the body. This is particularly important for drugs in suspension form, as it can influence the onset and intensity of the drug's action.<br /><br />2. **Recommended Sizes**:<br /> - **Fine Powder**: Median size between 125 µm to 180 µm.<br /> - **Very Fine Powder**: Median size ≤ 125 µm.<br /><br />3. **Purpose**: Using fine or very fine powders helps prevent unwanted sedimentation during or after preparation, ensuring uniform distribution of the drug throughout the suppository base.<br /><br />### Displacement Value<br /><br />1. **Definition**: The displacement value is a measure of how much of the base is displaced by a given mass of the drug. It is expressed as the mass of drug that displaces 1 gram of the base.<br /><br />2. **Calculation**:<br /> - **Variables**:<br /> - \( a \): Amount of pure base in a suppository without the drug.<br /> - \( d \): Amount of drug added.<br /> - \( c \): Amount of base after the drug is incorporated.<br /> - **Formula**: The displacement value can be calculated using the formula:<br /><br /> \[<br /> \text{Displacement Value} = \frac{d}{a - c}<br /> \]<br /><br /> This formula allows you to determine how much base is needed when a specific amount of drug is added to ensure the final suppository has the desired weight and composition.<br /><br />3. **Application**: Knowing the displacement value helps in accurately formulating suppositories by adjusting the amount of base used to accommodate the volume occupied by the drug, ensuring consistent dosage and effectiveness.<br /><br />By carefully considering both the particle size and displacement value, pharmacists can optimize the formulation of suspension suppositories for better therapeutic outcomes.