4.2 Selection of Excipients and APIs

The choice of excipients and APIs is critical to ensure proper incorporation and stability of the emulsion. Follow these steps to select the appropriate ingredients:

• 4.2.1 Select the oil phase based on the solubility of the lipophilic API (e.g., mineral oils, medium-chain triglycerides) or the compatibility with the hydrophilic API.
• 4.2.2 Choose emulsifiers with the appropriate hydrophilic-lipophilic balance (HLB) to stabilize the emulsion and promote API incorporation.
• 4.2.3 For water-in-oil emulsions, the API can be incorporated in the water phase, while for oil-in-water emulsions, the API can be dissolved in the oil phase.
• 4.2.4 Select co-surfactants or stabilizers, if necessary, to improve the emulsification process and API solubilization.

4.3 Incorporation of APIs into the Emulsion

4.3.1 Preparation of the Oil and Water Phases

• 4.3.1.1 Weigh the required amounts of oil phase, water phase, and API(s) as per the formulation protocol. Record the weights in the Batch Manufacturing Record (BMR).
• 4.3.1.2 Dissolve the API in the appropriate phase. For lipophilic APIs, dissolve them in the oil phase, while hydrophilic APIs should be dissolved in the aqueous phase.
• 4.3.1.3 Heat both the oil and water phases to the required temperature (typically 40°C-60°C) to ensure the components are fully dissolved and prepared for mixing.

4.3.2 Emulsion Formation

• 4.3.2.1 Slowly add the oil phase to the water phase (for oil-in-water emulsions) or the water phase to the oil phase (for water-in-oil emulsions) while continuously mixing with a high-shear mixer.
• 4.3.2.2 Adjust the mixing speed and temperature according to the formulation guidelines to form a stable emulsion. Continue mixing until the API is evenly distributed within the emulsion.
• 4.3.2.3 Optionally, pass the emulsion through a homogenizer for further droplet size reduction and improved stability.
• 4.3.2.4 Monitor the temperature throughout the process to avoid destabilization or degradation of the API.

4.4 Quality Control Testing

After incorporating the API into the emulsion, quality control tests must be conducted to ensure the API is properly encapsulated and the emulsion is stable. The following tests are recommended:

• 4.4.1 Measure the droplet size using a droplet size analyzer. The emulsion should have a uniform droplet size distribution, typically within the range of 100 nm to 10 µm.
• 4.4.2 Test the API content in the emulsion using an appropriate analytical method, such as HPLC, to confirm that the API concentration is within the specified range.
• 4.4.3 Conduct stability testing by storing the emulsion at room temperature and accelerated conditions (e.g., 40°C) and monitoring droplet size, API content, and phase separation over time.
• 4.4.4 Check the pH of the emulsion using a calibrated pH meter to ensure the pH is within the acceptable range for the product’s intended application.

4.5 Storage of Emulsion

The prepared emulsion should be stored in sterilized, airtight containers. Label the containers with the batch number, preparation date, and storage conditions. Store the emulsion at the recommended temperature (e.g., 4°C or room temperature), and periodically test for stability and API content retention.

5) Abbreviations, if any

• API: Active Pharmaceutical Ingredient
• HLB: Hydrophilic-Lipophilic Balance
• QA: Quality Assurance
• QC: Quality Control

6) Documents, if any

• Batch Manufacturing Record (BMR)
• Droplet Size Analysis Report
• API Content Analysis Report
• Stability Test Report

7) References, if any

• ICH Q8: Pharmaceutical Development Guidelines
• FDA Guidance on Emulsions for Drug Delivery

8) SOP Version

Version 1.0

Annexure

Annexure 1: Batch Manufacturing Record Template

 
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Batch No.
    
Oil Phase
    
Water Phase
    
API Type
    
API Concentration
    
Mixing Time
    
Droplet Size
    
Operator Initials
    
QA Signature
  
  

    
Batch Number
    
Oil Type/Weight
    
Water Type/Volume
    
API Name
    
Concentration (mg/mL)
    
Minutes
    
nm/µm
    
Operator Name
    
QA Name