Capsule: SOP for Developing Moisture Barrier Coatings for Capsules – V 2.0

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Capsule: SOP for Developing Moisture Barrier Coatings for Capsules – V 2.0

Standard Operating Procedure for Developing Moisture Barrier Coatings for Capsules

Department Capsule Manufacturing
SOP No. SOP/CM/042/2025
Supersedes SOP/CM/042/2022
Page No. Page 1 of 7
Issue Date 01/02/2025
Effective Date 05/02/2025
Review Date 01/02/2026

1. Purpose

The purpose of this SOP is to outline the process for developing moisture barrier coatings for capsules to protect the fill material from environmental conditions such as moisture and humidity. The barrier ensures that the capsules maintain their integrity, stability, and performance throughout their shelf life.

2. Scope

This SOP applies to the development of moisture barrier coatings for hard gelatin capsules in pharmaceutical manufacturing. It covers the selection of materials, formulation of coatings, and the application process.

3. Responsibilities

  • Formulation Development Team: Responsible for selecting suitable materials for the moisture barrier coating and developing the coating formulation.
  • Manufacturing Team: Responsible for applying the moisture barrier coating to the capsules, ensuring uniformity and quality throughout the process.
  • Quality Control (QC) Team: Responsible for testing the moisture barrier coatings to ensure that they meet the required specifications, including moisture resistance and adhesion strength.
  • Quality Assurance (QA) Team: Ensures that the development and application processes comply with GMP regulations and internal quality standards.

4. Accountability

The Capsule Manufacturing Supervisor is accountable for ensuring the development and application of the moisture barrier coating are executed as per this SOP. The QA Manager is responsible for reviewing the final product to confirm that it complies with all regulatory requirements and internal quality standards.

5. Procedure

5.1 Selection of Materials for Moisture Barrier Coatings

Before developing the moisture barrier coating, select appropriate materials based on the following considerations:

  1. Polymeric Materials

    1. Choose materials such as hydroxypropyl methylcellulose (HPMC), ethylcellulose, or shellac for their moisture barrier properties and compatibility with the capsule.
    2. Ensure that the selected material does not interfere with the dissolution or bioavailability of the API.
  2. Plasticizers

    1. Select plasticizers, such as glycerin or triacetin, that enhance the flexibility of the coating and improve its adhesion to the capsule shell.
  3. Solvents

    1. Choose appropriate solvents, such as ethanol or water, for dissolving the polymer and achieving the desired coating viscosity.
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5.2 Developing the Moisture Barrier Coating Formulation

The coating formulation should be developed by following these steps:

  1. Formulation of the Coating Solution

    1. Weigh the polymer, plasticizer, and solvent according to the formulation requirements.
    2. Dissolve the polymer in the solvent and mix until a homogeneous solution is achieved. Add the plasticizer to the solution and continue mixing to ensure uniform distribution.
  2. Adjust Viscosity

    1. Adjust the viscosity of the coating solution to ensure smooth application to the capsules. Viscosity should be suitable for the coating process, typically ranging from 30 to 50 centipoises.
  3. Optional Additives

    1. Add any additional additives to the formulation as needed, such as colorants or stabilizers, ensuring they do not compromise the moisture barrier properties.

5.3 Applying the Moisture Barrier Coating

The application of the moisture barrier coating involves the following steps:

  1. Prepare the Capsule Coating Equipment

    1. Ensure that the capsule coating machine is properly set up and cleaned before use. Check for appropriate equipment settings, such as speed and air pressure, to ensure optimal coating application.
  2. Coating Process

    1. Load the capsules into the coating drum or fluidized bed coater.
    2. Spray the coating solution onto the capsules evenly, ensuring that each capsule is fully coated with a thin, uniform layer of the barrier material.
    3. Monitor the coating process to ensure that the coating is applied consistently and that the capsules are not damaged.
  3. Drying the Coating

    1. Ensure proper drying of the coated capsules to prevent moisture absorption. Use controlled air flow and temperature to dry the coating without compromising the quality of the capsules.
    2. Verify that the moisture content of the final capsules is within acceptable limits.
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5.4 Testing the Moisture Barrier Coating

After the moisture barrier coating has been applied, perform the following tests:

  1. Moisture Barrier Performance

    1. Conduct a moisture permeability test to verify that the coating prevents the ingress of moisture. Test the capsules under standard conditions, such as 75% relative humidity, to assess the barrier’s effectiveness.
  2. Adhesion Strength

    1. Test the adhesion strength of the moisture barrier coating to ensure that it remains intact during manufacturing, handling, and storage. Use a peel or shear test method to assess the coating’s adhesion to the capsule shell.
  3. Coating Uniformity

    1. Perform visual inspections and weight checks to confirm the uniformity of the moisture barrier coating on the capsules.
  4. Stability Testing

    1. Conduct stability studies under various conditions (e.g., high humidity, temperature fluctuations) to assess the long-term efficacy of the moisture barrier coating.

5.5 Adjustments Based on Test Results

If the moisture barrier coating does not meet the required performance standards, take the following steps:

  1. Adjust Coating Formula

    1. If moisture permeability is too high, consider adjusting the polymer concentration, plasticizer type, or adding additional layers of coating.
  2. Modify Application Parameters

    1. If the coating is uneven or difficult to apply, adjust the spray rate, drying conditions, or capsule rotation speed during the coating process.

5.6 Documentation and Record-Keeping

Document all steps taken during the development and application of the moisture barrier coating:

  1. Coating Formulation Records

    1. Document all materials used in the coating formulation, including the polymer, plasticizers, solvents, and any additives.
  2. Batch Records

    1. Record all batch details, including the coating parameters, equipment settings, and any adjustments made during the process.
  3. Test Results

    1. Record the results of all performance tests, including moisture permeability, adhesion strength, and coating uniformity.
  4. Trial Reports

    1. Prepare a detailed trial report summarizing the development process, test results, and any adjustments made during the coating process.
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6. Abbreviations

  • SOP: Standard Operating Procedure
  • QA: Quality Assurance
  • QC: Quality Control
  • API: Active Pharmaceutical Ingredient
  • GMP: Good Manufacturing Practice
  • HPMC: Hydroxypropyl Methylcellulose

7. Documents

  1. Moisture Barrier Coating Formulation Record (Annexure-1)
  2. Moisture Barrier Coating Application Record (Annexure-2)
  3. Moisture Barrier Coating Test Results (Annexure-3)

8. References

  • USP <711> – Dissolution Testing
  • FDA Guidance for Industry: Stability Testing of Drug Products
  • International Conference on Harmonization (ICH) Guidelines for Pharmaceutical Development

9. SOP Version

Version: 2.0

10. Approval Section

Prepared By Checked By Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Moisture Barrier Coating Formulation Record

Material Weight Concentration Purpose
Hydroxypropyl Methylcellulose 100 g 5% Moisture barrier

Annexure-2: Moisture Barrier Coating Application Record

Batch ID Machine Settings Sealing Speed Coating Temperature
Batch 001 Speed: 100 rpm 50°C 45°C

Annexure-3: Moisture Barrier Coating Test Results

Test Type Result Specification Remarks
Moisture Permeability Pass Less than 0.5% No deviation

Revision History:

Revision Date Revision No. Revision Details Reason for Revision Approved By
01/01/2024 1.0 Initial Version New SOP Creation QA Head
01/02/2025 2.0 Updated coating application process Standardization QA Head
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