Statistical evaluation of the revised fixed-dose procedure

Area of Science:

• Toxicology
• Regulatory Science
• Animal Welfare

Background:

• The fixed-dose procedure (FDP), OECD Test Guideline 420, was developed as an alternative to the LD50 test for acute oral toxicity assessment.
• FDP reduces animal use and suffering while enabling hazard classification for regulatory purposes.
• Recent revisions aim for further refinement and alignment with the Globally Harmonized Hazard Classification and Labelling scheme (GHS).

Purpose of the Study:

• To describe the revised fixed-dose procedure (FDP) for acute oral toxicity testing.
• To analyze the properties and performance of the revised FDP using statistical modeling.
• To compare hazard classifications derived from the revised FDP with traditional LD50-based classifications.

Main Methods:

• Statistical modeling approach to analyze the revised FDP.
• Comparison of classification outcomes between the revised FDP and LD50-based methods (GHS and EU schemes).
• Evaluation of animal usage and outcomes in the revised FDP.

Main Results:

• The revised FDP generally classifies substances in the same or a more stringent hazard class compared to LD50 values under GHS and EU schemes.
• Classification consistency is higher for substances with steep dose-response curves and TD50 values near the LD50.
• The revised FDP typically involves five to six animals, with mortality in two or fewer cases.

Conclusions:

• The revised FDP is a robust and refined method for acute oral toxicity assessment.
• It provides reliable hazard classifications consistent with or more stringent than LD50-based methods.
• The procedure demonstrates improved animal welfare by minimizing animal use and mortality.