Standard Operating Procedure for Acid Resistance Testing for Enteric-Coated Tablets

Department	Tablet
SOP No.	SOP/TAB/095/2025
Supersedes	SOP/TAB/095/2022
Page No.	Page 1 of 7
Issue Date	01/03/2026
Effective Date	06/03/2026
Review Date	01/03/2027

1. Purpose

To define the procedure for testing the acid resistance of enteric-coated tablets, ensuring that the coating remains intact and protects the active pharmaceutical ingredient (API) from stomach acid, as per regulatory standards and product specifications.

2. Scope

This SOP applies to the testing of enteric-coated tablets for acid resistance to ensure that the coating protects the API under acidic conditions in the stomach, allowing for controlled release in the intestinal environment.

3. Responsibilities

• Manufacturing Personnel: Responsible for providing enteric-coated tablet samples for acid resistance testing and ensuring that the coating process adheres to the established SOP.
• Quality Control (QC): Responsible for conducting the acid resistance test, recording results, and ensuring that the tablets meet the required specifications for acid resistance.
• Quality Assurance (QA): Ensures that the acid resistance testing procedure is followed correctly and reviews the results for batch approval and regulatory compliance.

4. Accountability

The QC Manager is accountable for ensuring the acid resistance testing is conducted in compliance with this SOP. The QA Manager is responsible for reviewing the results and approving the batch for release.

5. Procedure

5.1 Sample Collection

1. Collect a representative sample of enteric-coated tablets from the batch, as specified in the batch record.
2. The sample should consist of a minimum of 6 tablets, or as specified in the batch record or pharmacopeial guidelines.
3. Ensure that the tablets are free from defects such as cracks, chips, or coating defects.
4. Label the sample appropriately for identification during testing.

5.2 Preparation of Testing Apparatus

1. Ensure that all testing equipment (e.g., dissolution apparatus, pH meters, and temperature controls) is clean, calibrated, and ready for use.
2. Prepare the dissolution apparatus, ensuring that it is fitted with the proper baskets or paddles and that the temperature and pH control systems are functioning correctly.
3. Prepare a simulated gastric fluid (SGF) solution with a pH of 1.2, and ensure that it is at the required temperature (usually 37 ± 0.5°C).

5.3 Performing Acid Resistance Test

1. Place the tablets into the dissolution apparatus, ensuring that they are properly aligned in the basket or paddle.
2. Start the dissolution apparatus and monitor the tablet behavior in the SGF solution for up to 2 hours, as specified in the pharmacopeial guidelines or batch record.
3. Ensure that the tablets do not show any signs of coating rupture or API release during the first 2 hours in the acidic environment.
4. After 2 hours, transfer the tablets to a simulated intestinal fluid (SIF) solution with a pH of 6.8 for further testing, to simulate the transition from the stomach to the small intestine.

5.4 Data Recording and Calculation

1. Record any observations during the test, including whether the tablets remained intact in the acidic environment and whether any coating detachment occurred (Annexure-1).
2. Note the time at which the tablets were transferred from the SGF solution to the SIF solution.
3. Ensure that the tablets maintain their integrity under acidic conditions before being exposed to the neutralizing environment.

5.5 Acceptance Criteria

1. Ensure that the tablets meet the following acceptance criteria:
   • No visible signs of coating rupture or API release during the first 2 hours in SGF.
   • The coating must withstand acidic conditions without failure.
   • Any tablets showing signs of coating failure during the test should be considered non-compliant.
2. If the test fails, investigate and document the findings in the deviation report (Annexure-2).
3. Take corrective actions as necessary and perform re-testing if required.

5.6 Documentation and Record-Keeping

1. Document all test results, including observations, timings, and any deviations from the acceptance criteria, in the batch record (Annexure-1).
2. Ensure that all records are signed, dated, and stored according to the company’s record retention policy for future audits and inspections.
3. Maintain all raw data, test results, and any supporting documentation for future reference and audits.

5.7 Post-Test Cleanup

1. Clean all equipment used for acid resistance testing, including the dissolution apparatus, sampling baskets, and sample containers, according to the cleaning SOP to prevent contamination between tests.
2. Ensure that the testing equipment is properly maintained and calibrated for future use.

6. Abbreviations

• SOP: Standard Operating Procedure
• GMP: Good Manufacturing Practice
• QC: Quality Control
• QA: Quality Assurance
• API: Active Pharmaceutical Ingredient
• SGF: Simulated Gastric Fluid
• SIF: Simulated Intestinal Fluid

7. Documents

1. Batch Record (Annexure-1)
2. Deviation Report (Annexure-2)

8. References

• USP <711> – Dissolution Testing
• 21 CFR Part 211 – Current Good Manufacturing Practice for Finished Pharmaceuticals (US FDA)
• European Pharmacopoeia (EP) – Acid Resistance Testing for Enteric-Coated Tablets

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Batch Record

Batch Number	Tablet Sample	SGF Time (hrs)	Coating Integrity	Result
Batch 001	Enteric-Coated Tablet	2	Intact	Pass

Annexure-2: Deviation Report

Deviation Date	Batch Number	Deviation Description	Corrective Action	Responsible Person
15/12/2025	Batch 001	Coating failure in SGF	Reworked coating process	Jane Doe

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 Testing Parameters	Refined acid resistance testing protocols	QA Head