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  6. Q&A: GFI #256 - Compounding Animal Drugs from Bulk Drug Substances
  1. Animal Drug Compounding

Q&A: GFI #256 - Compounding Animal Drugs from Bulk Drug Substances

Updated June 14, 2024 to add the Patient-Specific Prescriptions for Groups of Animals and Adverse Event Reporting sections.

Key Terms

Animal drug compounding” is the process of combining, mixing, or altering ingredients to create a medication tailored to the needs of an individual animal or a small group of animals. Animal drug compounders use either an FDA-approved drug (in its finished dosage form) or a bulk drug substance as the source of the active ingredient(s).

A “bulk drug substance,” can be thought of as the part of a compounded drug that creates the desired pharmacologic effect as an active ingredient. It’s also referred to as the active pharmaceutical ingredient (API). 

An “active moiety” is the molecule or ion that drives the action of the drug. For example, for the active ingredients erythromycin stearate, erythromycin ethylsuccinate, and erythromycin lactobionate, the active moiety is erythromycin. See 21 CFR 314.3 for the full regulatory definition.

Office stock” refers to compounded drugs kept on hand by veterinarians for patients. Office stock is generally compounded by a veterinarian, or by a pharmacist and sold to a veterinarian to have on hand, without a patient-specific prescription.

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