FDA Publishes Draft Guidance on Compounding Animal Drugs from Bulk Drug Substances
Authority: U.S. Food and Drug Administration (FDA), Center for Veterinary Medicine (CVM)
Document: Draft Guidance for Industry GFI #256B
Date: August 2026
Status: Draft – Not for Implementation
What’s New?
The U.S. FDA has issued GFI #256B, “Compounding Animal Drugs from Bulk Drug Substances: Compounding under CGMP in Federally-Registered Facilities.”
The draft guidance describes FDA’s proposed enforcement policy for animal drugs compounded from bulk drug substances (BDS) in federally registered facilities operating under current good manufacturing practice (CGMP).
The guidance is intended to be combined with GFI #256, “Compounding Animal Drugs from Bulk Drug Substances.”
Key Highlights
1. Patient-specific compounding
For nonfood-producing animals, FDA generally does not intend to take enforcement action for certain approval and adequate-directions-for-use violations when specified conditions are met, including state-law compliance, CGMP, applicable USP-NF standards, and a valid patient-specific prescription.
2. Office stock
The draft guidance covers office-stock animal drugs for nonfood-producing species when the drug is compounded from a BDS included on the applicable FDA list and other conditions are met.
3. Food-producing animals & wildlife
A limited pathway is described for antidotes for toxicoses in food-producing animals and sedatives/anesthetics for free-ranging wildlife. Applicable withdrawal-time and food-supply safeguards are required.
4. Clinical difference for copies
When a compounded drug is a copy of a marketed FDA-approved or indexed drug, a clinical difference for the identified patient may be required. Examples include formulation, strength, concentration, flavoring, or dosage-form changes. Price difference alone is not considered a clinical difference.
5. Adverse-event reporting
Federally registered facilities should report adverse events or product defects associated with compounded animal drugs using Form FDA 1932a within 15 business days after becoming aware of the event.
Regulatory Significance
The draft guidance provides greater clarity on FDA’s proposed enforcement priorities for animal drug compounding in federally registered facilities.
Regulatory and quality teams should monitor the final guidance, particularly for potential impacts on:
- CGMP compliance
- Bulk drug substance sourcing
- Prescription and distribution controls
- Product labeling
- Adverse-event reporting
- Documentation of clinical differences
- Applicable FDA bulk drug substance lists
Bottom Line
GFI #256B is a draft guidance and is not currently for implementation. FDA intends to use it to describe its enforcement approach toward qualifying animal drugs compounded from bulk drug substances under CGMP in federally registered facilities.