# Risk-Based Approach for Defining Retest Dates for Active Pharmaceutical Ingredients and Excipients

## TL;DR

This paper discusses how to determine retest dates for pharmaceutical ingredients using a risk-based approach to ensure quality and compliance.

## Contribution

The paper introduces a risk-based method for setting retest dates for drug substances and excipients.

## Key findings

- Regulatory guidelines require retesting of substances after the retest period for compliance.
- The phrase 'used immediately' is ambiguous and needs clearer interpretation.
- A risk-based approach helps establish retest dates and allowable usage time.

## Abstract

Drug substances and excipients must be stored in recommended storage conditions and should comply with their specifications during the retest period for their use in the manufacture of drug products. The ICH (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use) and WHO (World Health Organization) regulatory guidelines mandate that after the retest period, the drug substances must be retested for compliance with the specification and then used immediately in the manufacture of the finished product. Although these substances can be retested multiple times, an emphasis is placed on immediate use following a retest and compliance with standards. The phrase “used immediately” is ambiguous and is left for interpretation. In this article, we will look at the various processes that must be completed to determine the retest date. In addition, we present a risk-based method for establishing retest dates and the time during which material can be used.