gel products to ensure formulation stability and efficacy.

2. Scope

This procedure applies to R&D, formulation development, and quality assurance teams involved in new product development, reformulation, or scale-up of gel-based pharmaceutical products.

3. Responsibilities

• Formulation Scientist: To plan, conduct, and document compatibility studies for APIs in gel formulations.
• R&D Analyst: To assist with sample preparation, storage, and analytical testing of compatibility samples.
• Quality Assurance: To review documentation and verify adherence to procedures and regulatory standards.

4. Accountability

The Head – Gel Manufacturing and Head – Research & Development are accountable for ensuring compliance, traceability, and effectiveness of the API compatibility evaluations.

5. Procedure

5.1 Initial API Data Review

1. Collect technical data on the API including solubility profile, pKa, logP, hygroscopicity, thermal stability, and sensitivity to light or pH.
2. Review known incompatibilities from published literature, pharmacopeias, and supplier data sheets.

5.2 Selection of Excipients for Study

1. List all excipients to be evaluated including gelling agents, solvents, preservatives, humectants, and buffers.
2. Group excipients by function and physicochemical nature (e.g., ionic vs non-ionic).

5.3 Physical Compatibility Study

1. Mix API with each excipient in 1:1 ratio (by weight) and observe physical changes (color, odor, precipitation, liquefaction) at room temperature, 40°C, and 60°C for 14 days.
2. Photographically document physical changes and record data in Compatibility Observation Logbook (Annexure-1).

5.4 Chemical Compatibility Study

1. Prepare binary mixtures of API and each excipient in appropriate solvents (e.g., water, ethanol) and store under accelerated conditions (40°C ± 2°C / 75% RH ± 5%).
2. Analyze samples after 7, 14, and 28 days using HPLC or UV spectroscopy for content uniformity and degradation products.
3. Identify any new peaks or reduction in assay beyond ±5% limit.

5.5 Drug-Polymer Compatibility Study

1. Incorporate API into placebo gel matrices prepared with each candidate polymer (e.g., Carbopol 940, HPMC, Poloxamer).
2. Observe viscosity, pH, and visual appearance over 30 days under long-term and accelerated conditions.

5.6 Analytical Techniques

1. Use FTIR to identify chemical interactions by comparing spectra of mixtures against API and excipient individually.
2. Use DSC to analyze thermal behavior of mixtures and detect incompatibilities through endothermic or exothermic transitions.

5.7 Reporting and Conclusion

1. Document all findings in the API Compatibility Study Report (Annexure-2).
2. Include chromatograms, FTIR spectra, and thermal analysis data.
3. Conclude on compatibility and finalize excipient list for formulation development.

6. Abbreviations

• API: Active Pharmaceutical Ingredient
• DSC: Differential Scanning Calorimetry
• FTIR: Fourier Transform Infrared Spectroscopy
• HPLC: High-Performance Liquid Chromatography
• SOP: Standard Operating Procedure

7. Documents

1. Compatibility Observation Logbook – Annexure-1
2. API Compatibility Study Report – Annexure-2
3. Excipient Evaluation Checklist – Annexure-3

8. References

• ICH Q9 – Quality Risk Management
• USP General Chapter <1225> – Validation of Compendial Procedures
• WHO Technical Report Series No. 1010 – Annex 3

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation	Jr. Production Chemist	QA Executive	Head – Manufacturing
Department	Gel Manufacturing	Quality Assurance	Manufacturing

11. Annexures

Annexure-1: Compatibility Observation Logbook

Excipient Name	API Name	Storage Temp	Observation Day 7	Day 14	Day 28
Carbopol 940	Ketoprofen	40°C	No change	Slight discoloration	No precipitation

Annexure-2: API Compatibility Study Report

• API: Diclofenac Sodium
• Polymers Tested: HPMC, Carbopol, Poloxamer
• Best Polymer Match: Carbopol 940
• Observed Issues: None

Annexure-3: Excipient Evaluation Checklist

• Excipient purity confirmed: Yes
• Compatibility with API: Yes
• Regulatory Acceptability: Yes

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
02/06/2022	1.0	Initial issue	New SOP implementation	QA Head
02/06/2025	2.0	Expanded to include drug-polymer interaction studies	Regulatory requirement	QA Head