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How a substance gets onto FDA's 503A bulks list, and why it still holds only six

By Peptide Policy Watch staff · Published October 30, 2026 · 8 min read · 10 sources, 10 checked at the source

Every story about compounded peptides runs into the same short list sooner or later. HHS's new policy says BPC-157, TB-500 and four other peptides can't simply be added to it without FDA rulemaking. So what is the 503ASection of federal drug law covering compounding by state-licensed pharmacies and doctors, usually for a prescription written for one patient. Glossary entry bulks list, who decides what goes on it, and why has it moved so slowly? Here is the path a substance takes, step by step, from a public nomination to a line in the Code of Federal Regulations.

Facts are as of October 30, 2026. Sources, with retrieval dates, are at the bottom.

• 3routes in the law for a bulk ingredient to be used in 503A compounding [V]
• 6substances on the 503A bulks list today, all non-peptides [V]
• 29 yearssince Congress created the list's legal basis in 1997 [V]

The three doors in the law

Section 503A of the Food, Drug, and Cosmetic Act covers compounding by state-licensed pharmacists and licensed physicians. It sets three ways a bulk drug substance can qualify. [V]

1. A USP or NF monograph. If the U.S. Pharmacopeia or National Formulary has a quality standard for the substance, compounders can use it if it meets that standard. [V]
2. A component of an approved drug. If no monograph exists, the substance can still qualify when it is part of an FDA-approved drug. [V]
3. The bulks list. If neither applies, the substance has to appear on a list FDA builds through regulation. [V]

Whichever route applies, the ingredient also has to come from an FDA-registered manufacturer with a valid certificate of analysis. [V] Most wellness peptides have no monograph and no approved product, so the list is the only door open to them. [S]

Step 1: Someone nominates the substance

FDA's 503A page says the agency asked the public for nominations in 2015. [V] Pharmacies, physicians and trade groups sent in names with supporting information. While FDA works through them, its interim policy from June 2016 sorts nominated substances into categories. [V] For Category 1An interim FDA group of nominated bulk ingredients that FDA generally does not object to pharmacies using while its review continues. Not an approval. Glossary entry, FDA says it doesn't intend to act against compounders who meet the policy's conditions. Category 2An interim FDA group of nominated bulk ingredients that FDA has flagged for possible significant safety risks while its review continues. Glossary entry covers substances where FDA has identified what it calls significant safety risks, and Category 3 covers nominations FDA says lacked enough information to evaluate. [V] Our categories explainer covers how these work.

One change matters for anyone nominating something new. FDA's page says that anything nominated from January 7, 2025 onward won't be sorted into these categories. [V] Nominations are still open, and FDA says it will keep evaluating well-supported ones. [V] A substance nominated today gets no interim category while it waits.

Step 2: FDA evaluates it against four criteria

The regulation at 21 CFR 216.23 lists what FDA weighs. [V]

• the substance's physical and chemical characterization
• any safety issues raised by its use in compounded drugs
• evidence of effectiveness, or lack of it, if any exists
• historical use in compounding, including the conditions it was used for and the peer-reviewed literature

The statute itself requires historical use and peer-reviewed reports among the criteria. [V] For a peptide with years of clinical use in compounding but few published trials, the historical-use criterion is where practitioners' experience can enter the record. [S]

Step 3: The advisory committee and USP weigh in

Before FDA writes this kind of regulation, the law requires it to meet with and seek advice from a compounding advisory committee, with an exception when FDA finds that moving first is needed to protect public health. [V] The statute spells out its makeup: members drawn from the U.S. Pharmacopeia, the state pharmacy boards' national association, pharmacist, physician and consumer groups, and other experts. [V] The law also requires FDA to consult the U.S. Pharmacopeia on the list itself. [V]

For peptides, this is the Pharmacy Compounding Advisory Committee (PCACPharmacy Compounding Advisory Committee: outside experts who advise FDA on compounding questions. Its votes are recommendations, not decisions. Glossary entry) that met in July 2026 on seven peptides. The next meeting, before the end of February 2027, will take up LL-37, GHK-Cu, dihexa, melanotan II and PEG-MGF. We cover it here. [V] A committee vote is advice. FDA still makes the call. [V]

Step 4: A proposed rule, comments and a final rule

The list lives in the Code of Federal Regulations, so changing it takes rulemaking. [V] FDA proposes changes in a Federal Register notice, takes public comments, then publishes a final rule with an effective date. FDA's page says it handles sufficiently supported nominations "on a rolling basis through notice-and-comment rulemaking." [V]

The record shows how long each round has taken. [V]

What is on the list now

The six substances on the list are Brilliant Blue G, cantharidin, diphenylcyclopropenone, N-acetyl-D-glucosamine, squaric acid dibutyl ester and thymol iodide. Five of the six are limited to topical use. [V] The regulation separately lists four substances FDA considered and turned down: oxitriptan, piracetam, silver protein mild and tranilast. [V]

The 2019 proposal would have added five substances: L-citrulline, glycolic acid, pyruvic acid, glutaraldehyde and trichloroacetic acid. [V] It also proposed turning down 26 others. That list includes vasoactive intestinal peptide, NAD and curcumin, which shows that peptides and wellness ingredients have been in the queue for years. [V]

The regulation adds one more rule. Listing a substance doesn't make compounded products made with it FDA-approved, and calling them approved or FDA-endorsed makes them misbranded. [V]

Why the pace matters for peptides

Congress asked for this list in 1997. Twenty-nine years later it holds six items, and the only proposal to expand it has waited seven years for a final rule. [V] For peptides that patients and practitioners want to use, that pace leaves the interim categories, and now HHS's enforcement policy, doing work the list was meant to do. [S]

HHS's October 2026 policy says as much in its own way. It covers six peptides, BPC-157, TB-500, epitalon, KPV, MOTS-c and semax, and says comments on it may give FDA more evidence "in rulemaking to address some or all of the substances." [V] HHS describes the policy as one that "advances patient choice and freedom," and it ties the policy's life to the list: it applies until a final rule decides whether each peptide is on the list or not. [V] Our policy brief has the details, and the comment window closes at 11:59 PM Eastern on November 13, 2026, per the regulations.gov docket. [V] An enforcement policy can be changed or withdrawn more easily than a regulation, which is why advocates for access often treat a final listing as the lasting win. [S]

Limits and unknowns

• We searched the Federal Register for FDA rules and proposed rules on the 503A bulks list. A final rule could be in clearance that isn't public yet. [U]
• We don't know when FDA will propose rules for any peptide, or which way it would go. [U]
• The 503BSection of federal drug law for outsourcing facilities: larger compounders that register with FDA and must follow drug-manufacturing quality rules. Glossary entry list for outsourcing facilities works differently and is not covered here.

Sources (retrieved October 30, 2026)

1. 21 U.S.C. 353a (FD&C Act section 503A), via Cornell Legal Information Institute, including the 1997 enactment and 2013 amendment notes [V] — https://www.law.cornell.edu/uscode/text/21/353a
2. eCFR, 21 CFR 216.23, Bulk drug substances that can be used to compound under section 503A, as of October 28, 2026 [V] — https://www.ecfr.gov/current/title-21/chapter-I/subchapter-C/part-216/subpart-B/section-216.23
3. FDA, "Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act," content current as of May 14, 2026 [V] — https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act
4. Federal Register, final rule, 84 FR 4696, February 19, 2019, effective March 21, 2019 [V] — https://www.federalregister.gov/documents/2019/02/19/2019-02367/list-of-bulk-drug-substances-that-can-be-used-to-compound-drug-products-in-accordance-with-section
5. Federal Register, proposed rule, 84 FR 46688, September 5, 2019 [V] — https://www.federalregister.gov/documents/2019/09/05/2019-18951/amendments-to-the-list-of-bulk-drug-substances-that-can-be-used-to-compound-drug-products-in
6. Federal Register, proposed rule, 81 FR 91071, December 16, 2016 [V] — https://www.federalregister.gov/documents/2016/12/16/2016-30109/list-of-bulk-drug-substances-that-can-be-used-to-compound-drug-products-in-accordance-with-section
7. Federal Register, interim policy guidance notice, 81 FR 37502, June 10, 2016 [V] — https://www.federalregister.gov/documents/2016/06/10/2016-13799/interim-policy-on-compounding-using-bulk-drug-substances-under-section-503a-of-the-federal-food-drug
8. Federal Register API search of FDA rules and proposed rules on the 503A bulks list (14 results, 1998 to 2019) [V] — https://www.federalregister.gov/api/v1/documents.json?conditions[term]=503A+bulk+drug+substances+list&conditions[agencies][]=food-and-drug-administration
9. HHS, "Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances" [V] — https://www.hhs.gov/sites/default/files/hhs-503a-peptide-enforcement-discretion-policy-appendix-b.pdf
10. Regulations.gov, docket HHS-OASH-2026-0496 [V] — https://www.regulations.gov/docket/HHS-OASH-2026-0496

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