Guidelines for Stability Testing of Drug Product Impurities
1) Purpose
The purpose of this SOP is to provide a standardized procedure for assessing the stability of impurities in drug products. Stability testing ensures that impurities remain within acceptable limits and do not compromise the safety or efficacy of the product throughout its shelf life.
2) Scope
This SOP applies to all drug products produced, handled, or stored by the organization that require impurity testing to ensure compliance with regulatory requirements. It is intended for personnel involved in formulation development, quality control, and regulatory compliance.
3) Responsibilities
Formulation Scientist: Responsible for designing the stability study protocol and selecting appropriate impurity testing methods.
Quality Control (QC) Team: Responsible for conducting impurity tests according to the approved protocol and documenting results.
QA Team: Responsible for reviewing data, ensuring regulatory compliance, and approving the final stability report.
4) Procedure
4.1 Study 
- Identify critical impurities that require monitoring based on the drug product’s formulation and degradation profile.
- Select appropriate analytical methods (e.g., HPLC, GC-MS) to quantify and identify impurities.
- Define storage conditions (e.g., room temperature, refrigerated) based on the product’s characteristics and regulatory guidelines.
- Develop a study protocol outlining the objectives, sampling schedule, and analytical methods to be used.
4.2 Sample Preparation:
- Prepare samples from representative production batches and label them with batch numbers, storage conditions, and sampling time points.
- Store samples in designated stability chambers under specified conditions.
4.3 Testing Schedule:
- Conduct initial testing on all samples to establish baseline data for impurity levels.
- Perform follow-up testing at predetermined intervals (e.g., 1 month, 3 months, 6 months) to monitor changes in impurity levels over time.
- Document all test results and analyze data for trends or deviations from acceptance criteria.
4.4 Data Analysis and Reporting:
- Analyze data using statistical methods to determine trends in impurity levels and compliance with acceptance criteria.
- Prepare a stability study report summarizing findings, conclusions, and recommendations for storage and handling conditions.
- Submit the report for QA review and archiving.
5) Abbreviations, if any
QC: Quality Control
QA: Quality Assurance
HPLC: High-Performance Liquid Chromatography
GC-MS: Gas Chromatography-Mass Spectrometry
6) Documents, if any
Impurity Stability Protocol: Document detailing the study plan and methodology.
Analytical Data Records: Data sheets for all tests performed.
7) Reference, if any
ICH Q3B(R2): Impurities in New Drug Products
ICH Q1A(R2): Stability Testing of New Drug Substances and Products
8) SOP Version
Version 1.0