Gel Manufacturing: SOP for Evaluating API Compatibility in Gels – V 2.0

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Gel Manufacturing: SOP for Evaluating API Compatibility in Gels – V 2.0

Standard Operating Procedure for Assessing API Compatibility in Gel Formulations


Department Gel Manufacturing
SOP No. SOP/GM/013/2025
Supersedes SOP/GM/013/2022
Page No. Page 1 of 14
Issue Date 02/06/2025
Effective Date 04/06/2025
Review Date 02/06/2026

1. Purpose

The purpose of this SOP is to define a standardized procedure for evaluating the compatibility of Active Pharmaceutical Ingredients (APIs) with excipients, gelling agents, preservatives, and other formulation components used in

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.
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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.
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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
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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
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