Bulk drug substance
A bulk drug substance is the raw active ingredient used to make a compounded medicine, before it is turned into a finished product. Rules limit which ingredients compounders may use. The rules exist so that patients get ingredients with a known identity and quality.
For experts
Under 21 CFR 207.1, a bulk drug substance as referenced in sections 503A(b)(1)(A) and 503B(a)(2) of the FD&C Act means the same as an active pharmaceutical ingredient: a substance intended to furnish pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment or prevention of disease, or to affect the structure or function of the body. FDA requires compounders to use substances that meet a monograph, are components of approved drugs, or appear on the relevant bulks list, with a valid certificate of analysis and an FDA-registered manufacturer.
Sources (3)
- 0121 CFR 207.1 - What definitions and interpretations of terms apply to this part?Electronic Code of Federal Regulations (eCFR), Office of the Federal Register · 2026-09-25 · accessed 2026-09-29
- 02Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C ActU.S. Food and Drug Administration · 2026-05-14 · accessed 2026-09-29
- 03Bulk Drug Substances Used in Compounding Under Section 503B of the FD&C ActU.S. Food and Drug Administration · 2025-01-07 · accessed 2026-09-29