Bulk Drug Substances Used in Compounding

Compounders sometimes produce drugs using bulk drug substances, also known as active pharmaceutical ingredients. For example, when a patient has an allergy to an ingredient in an FDA-approved drug, a state-licensed pharmacist or physician, or an outsourcing facility, might compound a drug product using a bulk drug substance that does not contain the allergen.

However, because compounding from bulk drug substances presents risks to patients, sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act place limits on the bulk drug substances that can be used in compounding.  

State-licensed physicians and pharmacists seeking to operate under section 503A, may only use bulk drug substances in compounding drug products that:

  • comply with an applicable United States Pharmacopeia (USP) or National Formulary (NF) monograph if one exists, and the USP chapter on pharmacy compounding;
  • are components of FDA-approved drug products if an applicable USP or NF monograph does not exist; or
  • appear on FDA’s list of bulk drug substances that can be used in compounding (the 503A) if such a monograph does not exist and the substance is not a component of an FDA-approved drug product.

Outsourcing facilities, which register with FDA, compound under section 503B, and may only use bulk drug substances in compounding that:

  • Are used to compound drug products that appear on FDA’s drug shortage list at the time of compounding, distribution, and dispensing; or
  • Appear on FDA’s list of bulk drug substances for which there is a clinical need (the 503B bulks list).

FDA is working to develop the 503A bulks list and 503B bulks list. These lists will be updated on an ongoing basis as the agency evaluates bulk drug substances nominated for these lists.

Page Last Updated: 03/01/2019
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