results are reviewed and documented for regulatory compliance.

Regulatory Affairs: Ensures that the compatibility studies meet all regulatory guidelines and documentation requirements for market approval.

4. Accountability

The Head of Creams Manufacturing is responsible for overseeing the compatibility studies of APIs and excipients. The QA Manager is accountable for reviewing the results of the compatibility studies and ensuring that all necessary actions are taken based on the findings.

5. Procedure

5.1 Selection of APIs and Excipients

1. Select the APIs and excipients to be included in the cream formulation based on their intended purpose (e.g., moisturizing, anti-aging, therapeutic effects) and regulatory requirements.
2. Choose excipients that complement the APIs in terms of their functionality and stability. Consider the impact of excipients on the cream’s texture, appearance, viscosity, and shelf life.
3. Gather data on the selected APIs and excipients, including their known interactions, stability profiles, and any potential contraindications.

5.2 Conducting Compatibility Studies

1. Compatibility studies should be conducted under various conditions to assess the impact of interactions between the API and excipients. These studies typically include:
   • Physical Compatibility: Evaluate any changes in appearance, color, texture, or consistency of the cream formulation when APIs are combined with excipients.
   • Chemical Compatibility: Assess any chemical interactions between the APIs and excipients that may result in degradation, inactivation, or formation of undesirable by-products.
   • Functional Compatibility: Test whether the selected excipients maintain the desired functionality of the cream, such as spreadability, absorption, and stability, when combined with the APIs.
2. Conduct testing at various time points and under different conditions (e.g., temperature, humidity) to mimic real-world storage conditions and assess long-term compatibility.
3. Prepare small-scale laboratory samples to evaluate the interactions between APIs and excipients. These samples should be representative of the final cream formulation.

5.3 Analytical Testing of Compatibility

1. Perform the following analytical tests to evaluate the compatibility of the API-excipient combinations:
   • Viscosity Testing: Assess any changes in the cream’s viscosity due to API-excipient interactions.
   • pH Testing: Ensure that the pH of the formulation remains within an acceptable range after API-excipient mixing.
   • Stability Testing: Conduct accelerated stability tests to evaluate any physical or chemical changes in the cream over time.
   • Active Ingredient Analysis: Analyze the concentration of the API in the cream formulation to ensure no loss or degradation occurs during the formulation process.
2. Perform these tests at various stages of formulation and production to ensure that the formulation is stable and does not show signs of incompatibility.

5.4 Documentation of Compatibility Results

1. Document all compatibility study results, including the following:
   • List of APIs and excipients tested
   • Test methods used (e.g., viscosity, pH, stability)
   • Test results for each combination
   • Any observed incompatibilities or changes in product characteristics
   • Corrective actions taken (if applicable)
2. Prepare a Compatibility Study Report (Annexure-1) summarizing the findings and conclusions of the study, including recommendations for proceeding with or adjusting the formulation.
3. The Compatibility Study Report should be reviewed and approved by the QA team before moving forward with the formulation development process.

5.5 Approval and Finalization of Formulation

1. After the compatibility studies are completed and reviewed, finalize the formulation for production. If any issues were identified, modify the formulation by selecting alternative excipients or adjusting concentrations to mitigate the risks.
2. Once the formulation is deemed compatible and stable, it can proceed to the next stage of development, such as stability testing or scale-up for commercial production.
3. Ensure that all compatibility study records are archived for future reference and regulatory compliance purposes.

6. Abbreviations

• QC: Quality Control
• QA: Quality Assurance
• GMP: Good Manufacturing Practices
• API: Active Pharmaceutical Ingredient

7. Documents

1. Compatibility Study Report (Annexure-1)
2. Formulation Development Log (Annexure-2)
3. Stability Testing Report (Annexure-3)

8. References

• Good Manufacturing Practices (GMP) Guidelines – 21 CFR Part 211
• International Conference on Harmonisation (ICH) Q7 – Good Manufacturing Practice for Active Pharmaceutical Ingredients
• Pharmacopeial Monographs for Cream Formulations

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Compatibility Study Report

API	Excipient	Test Method	Test Result	Observations
Vitamin C You said: C ChatGPT said: Here is the continuation of SOP for Compatibility Studies of APIs and Excipients in Cream Formulations under the Creams department (SOP/CRM/028/2025): html Copy	Vitamin C	Ascorbic acid	Viscosity Testing	Pass	No changes in cream consistency
Hyaluronic Acid	Glycerin	Stability Testing	Pass	No separation observed after 6 months of storage

Annexure-2: Formulation Development Log

Formulation Name	Batch Number	APIs	Excipients	Compatibility Testing Outcome
Hydrating Cream	12345	Vitamin C, Hyaluronic Acid	Glycerin, Carbomer	All tests passed, formulation stable

Annexure-3: Stability Testing Report

Test Type	Result	Test Date	Approval Status
Real-time Stability	Pass	12/07/2025	Approved
Accelerated Stability	Pass	12/07/2025	Approved

Revision History:

Revision Date	Revision No.	Revision Details	Reason for Revision	Approved By
01/03/2024	1.0	Initial Version	New SOP Creation	QA Head
01/03/2025	2.0	Format Revision and Updates	Standardization of Document	QA Head