FDA Finalizes Standards for Assessing Reproductive and Genotoxicity Risks from Veterinary Drug Residues

The U.S. Food and Drug Administration’s Center for Veterinary Medicine (FDA-CVM) has finalized two revised guidance documents establishing internationally harmonized approaches for evaluating reproductive toxicity and genotoxicity associated with veterinary drug residues in human food.

Issued September 1, 2026, the two documents are CVM GFI #115 (VICH GL22 Revision 1), Reproduction Testing, and CVM GFI #116 (VICH GL23 Revision 2), Genotoxicity Testing. Both are based on the International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products (VICH) framework.

Why the change matters

The guidance addresses a distinctive food-safety problem: people may consume very low concentrations of veterinary drug residues over prolonged periods, potentially including lifetime exposure. FDA and VICH therefore use toxicological testing designed to detect hazards that may not be adequately characterized by shorter-duration studies.

The revised reproduction guidance specifically seeks international harmonization of testing for reproductive effects associated with long-term, low-dose exposure to veterinary drug residues. It covers effects on male and female fertility, mating, conception, implantation, pregnancy, parturition, lactation, offspring survival and development, sexual maturation and subsequent reproductive function.

Importantly, the revised framework recognizes that residue exposure differs from conventional human pharmaceutical exposure. Because food-residue exposure may continue over multiple generations, VICH considers multigeneration testing and extended one-generation reproductive toxicity studies (EOGRTS) appropriate tools for assessing potential effects. OECD Test Guidelines 416 and 443 are identified as reference methods.

Genotoxicity framework becomes more explicitly standardized

The revised GFI #116 / VICH GL23(R2) establishes a standardized battery for identifying the genotoxic potential of veterinary drug residues, including parent compounds and, where relevant, metabolites.

Two testing options are recognized:

FDA/VICH considers both options suitable for hazard identification, but Option 1 is generally preferred where the 3Rs principle can be applied, unless there is scientific justification for Option 2 or the additional in-vivo test can be incorporated into an existing repeat-dose study without increasing animal use.

The framework incorporates OECD testing methodologies, including bacterial reverse mutation, mammalian-cell micronucleus or chromosome-aberration testing, mammalian-cell gene mutation assays and in-vivo micronucleus, chromosome-aberration, comet or transgenic-rodent mutation assays.

Greater attention to metabolites

A significant scientific consideration is that assessment does not necessarily stop with the parent veterinary drug.

The revised genotoxicity guidance states that major metabolites occurring as residues in food may also require testing, particularly when a metabolite is produced in the target animal but not in the laboratory species or contains structural alerts for genotoxicity.

The guidance defines major metabolites, in relevant circumstances, as those comprising ≥100 µg/kg or ≥10% of total residue in samples collected during target-animal metabolism studies.

This strengthens the connection between residue chemistry, metabolism studies and toxicological risk assessment rather than treating the parent drug molecule in isolation.

Implications for veterinary pharmaceutical development

The regulatory significance extends beyond FDA review. VICH was established to facilitate the mutual acceptance of safety data among participating regulatory authorities. The revised documents were developed with consideration of regulatory and scientific practices in the United States, European Union, Japan, Australia, Canada, New Zealand and the United Kingdom.

For veterinary pharmaceutical developers, greater harmonization can potentially reduce duplication in safety programs and provide a more predictable framework for designing residue toxicology packages for multiple markets.

The revised approach also explicitly supports the 3Rs — replacement, reduction and refinement of animal use. FDA/VICH encourages integration of in-vivo genotoxicity testing into repeat-dose toxicity studies wherever scientifically appropriate.

What changes for industry

The immediate impact is primarily on development strategy and regulatory evidence generation, rather than on permitted residue concentrations.

Genotoxicity results generally do not directly determine the numerical value of an acceptable daily intake (ADI), but they can influence whether additional carcinogenicity testing is warranted and whether an ADI can ultimately be established.

The revised standards therefore reinforce a more integrated safety assessment:

Veterinary drug → metabolism → parent drug/metabolites → residue exposure → reproductive/genotoxicity testing → carcinogenicity assessment where indicated → ADI → food-safety risk assessment

For companies developing veterinary pharmaceuticals for food-producing species, this makes early consideration of metabolite profiles, structural alerts, exposure duration, test selection and cross-regional regulatory requirements increasingly important.

Regulatory clarification

These documents are FDA guidance, not new regulations. FDA explicitly states that its guidance documents generally do not establish legally enforceable responsibilities and instead describe the Agency’s current recommendations unless a specific statutory or regulatory requirement applies.

Bottom line

The September 1 action represents an important update to the scientific infrastructure underpinning the safety assessment of veterinary drug residues in food. Its significance lies less in introducing new residue limits and more in strengthening internationally harmonized, science-based toxicology standards, particularly for long-term exposure, reproductive effects, genotoxicity and relevant metabolites.

Industry implication

Veterinary drug developers targeting food-producing animals should treat the revised VICH standards as an important reference point for future toxicology programs, particularly where products or metabolites could generate reproductive or DNA-damage concerns.