How a substance gets on the 503A list: the nomination process, step by step

Why the list exists

Section 503A of the Food, Drug, and Cosmetic Act lets a licensed pharmacist compound a drug for an individual patient without the approval, manufacturing and labelling requirements that apply to ordinary drugs, as long as a set of conditions is met. One condition concerns the active ingredient. A pharmacy may compound from a bulk drug substance that complies with a USP or National Formulary monograph; if no monograph exists, from one that is a component of an FDA-approved drug; and if it is neither, only from one that appears on a list FDA develops through regulations (statute) ¹.

That third route is the 503A bulks list. It matters for peptides because almost none of the popular ones has a monograph or is part of an approved drug, so the list is the only door. Our guide to Category 1, Category 2, 503A and 503B explains how the list relates to FDA's interim categories; this article follows the path a substance takes to get onto it.

What is on the list today

The list is codified at 21 CFR 216.23. As of the version current on September 1, 2026, it names six substances: Brilliant Blue G, and five for topical use only, cantharidin, diphenylcyclopropenone, N-acetyl-D-glucosamine, squaric acid dibutyl ester and thymol iodide. The same section names four substances FDA has decided not to include: oxitriptan, piracetam, mild silver protein and tranilast (regulation) ². No peptide appears in either part.

The section also carries a warning that appears on no other kind of drug list. It states that the available evidence is inadequate to show any drug compounded from a listed substance is safe or effective, and that anyone who represents such a compounded drug as FDA-approved or endorsed causes it to be misbranded (regulation) ². Being on the list means a pharmacy may use the ingredient, not that FDA vouches for the result.

The list was first set by a final rule published on February 19, 2019 (regulation) ³. A September 2019 proposal would have added five more substances, among them glycolic acid and L-citrulline, after advisory committee votes in their favour (proposed rule) ⁴; none of the five appears in the current list, a reminder that a proposal is not the end of the process.

Step 1: someone nominates the substance

FDA does not choose candidates on its own. In 2015 it opened public docket FDA-2015-N-3534, where interested groups and individuals can nominate a substance that was not previously nominated, renominate one whose earlier nomination lacked enough supporting information, or comment on nominated substances (Federal Register notice) ⁵. The docket is still the entry point; FDA described it in its 2019 rule as open to new nominations and renominations, evaluated on a rolling basis (regulation) ³.

A nomination is meant to be substantive. FDA's notice asks for information identifying the substance and showing it meets the definition of a bulk drug substance, the dosage forms and routes it will be compounded into, the rationale for using it, its past use in compounding and the supporting literature, and anything else relevant to the evaluation (Federal Register notice) ⁵. Pharmacies, compounding trade groups, clinicians and patients have all filed nominations, and each one becomes part of the public record in the docket, where FDA can draw on it years later when it finally reaches that substance.

Step 2: FDA decides whether the nomination can be evaluated

A nomination without enough information goes nowhere. FDA's 2015 notice warns that if the supporting information received for a substance is inadequate, the agency will be unable to consider it further for the list (Federal Register notice) ⁵. Substances nominated with adequate support are the ones FDA evaluates, and under its interim policy they can be placed in Category 1 while the evaluation runs (regulation) ³.

The nomination also has to be for a genuine bulk drug substance, the active ingredient itself, rather than a finished product or a mixture.

Step 3: FDA weighs four criteria

FDA evaluates each candidate against four criteria set out in the regulation: the physical and chemical characterisation of the substance; any safety issues raised by its use in compounded drugs; the available evidence of effectiveness or lack of effectiveness of a drug compounded with it, if any exists; and its historical use in compounding, including the conditions treated and references in peer-reviewed literature (regulation) ². The statute itself requires that the criteria include historical use and reports in peer-reviewed medical literature (statute) ¹.

FDA balances the four rather than requiring all of them. A substance with little effectiveness evidence can still be listed if it is well characterised, safe in the proposed use and has a long history in compounding, which is roughly the profile of the topical agents now on the list. For peptides the weak points are usually characterisation, impurities and immune reactions, and the absence of human data, which FDA staff have repeatedly cited.

Step 4: the advisory committee

Before FDA issues a regulation adding substances to the list, the statute requires it to convene and consult an advisory committee on compounding, unless it decides that acting first is necessary to protect public health; the committee must include representatives of the National Association of Boards of Pharmacy, the United States Pharmacopeia, pharmacy, physician and consumer organisations (statute) ¹. That body is the Pharmacy Compounding Advisory Committee, and the statute also requires consultation with USP.

FDA prepares briefing documents with its staff's evaluation and a recommendation for each substance, the committee hears presentations and public comment, and it votes. The vote is advice, recorded substance by substance with the reasons members give. FDA usually follows it but is not bound by it. The agency has said it will not propose listing a substance without consulting USP and the committee (regulation) ³, and in July 2026 the committee disagreed with the agency's own staff on six of seven substances.

Step 5: rulemaking

Only a regulation changes the list. After the committee meeting, FDA decides whether to propose adding each substance, publishes a proposed rule in the Federal Register, takes public comment, and then publishes a final rule that amends 21 CFR 216.23. The 2019 proposal shows the pattern: FDA cited the committee's votes and USP consultation when it proposed five additions (proposed rule) ⁴. Members of the public can also petition FDA to amend the list under its general citizen-petition rule (proposed rule) ⁴.

No deadline forces FDA to move from a committee vote to a proposal, or from a proposal to a final rule. Years can pass, and as the 2019 proposal shows, a proposal can stall. For anyone waiting on a particular substance, the absence of a proposed rule is the clearest sign that nothing has changed yet.

The interim categories that run alongside

Because building the list by regulation is slow, FDA sorts nominated substances into interim categories while it works. Category 1 holds substances nominated with adequate support that FDA is evaluating and, under its interim policy, does not intend to act against pharmacies for compounding with them in the meantime; Category 2 holds substances that raise significant safety risks; Category 3 holds nominations without enough supporting information (FDA guidance) ⁶. The categories are FDA policy, not law, and can change without rulemaking, which is how twelve peptides left Category 2 in April 2026.

A substance's category and its place on the list are separate questions. Category 1 offers a temporary tolerance; only the list in 21 CFR 216.23 gives a permanent legal basis. Our guide to the categories lists where each peptide sits.

How to follow the process, or take part

The process is public at almost every step. Nominations and comments are filed in docket FDA-2015-N-3534 on Regulations.gov, where anyone can read what has been submitted for a substance (Federal Register notice) ⁵. FDA announces advisory committee meetings in the Federal Register with a separate docket for written comment, posts its briefing documents in advance, and allows oral public comment at the meeting; the July 2026 meeting used docket FDA-2025-N-6895 (FDA briefing document) ⁷. A proposed rule opens its own comment period.

Comments that add evidence carry the most weight, because FDA evaluates substances against its four criteria rather than by counting support. Characterisation data, safety reports and published human studies speak directly to those criteria; testimonials do not.

The 503B list is a separate process

Outsourcing facilities registered under section 503B have their own bulks list, built through a different standard: a clinical need for compounding with the substance. A decision on one list does not carry over to the other. Our category guide covers the 503B side, including FDA's proposal to keep semaglutide, tirzepatide and liraglutide off that list.

The 2026 cycle as a worked example

The 2026 peptide cycle followed every step and shows where it can surprise. In April 2026 FDA removed twelve peptides from Category 2 of its interim policy, which takes them off the formal safety-concern list without making them usable. Seven of them went to the committee, which met on July 23 and 24, 2026, under docket FDA-2025-N-6895. FDA's staff recommended adding none. The committee voted to recommend six, BPC-157, KPV, TB-500, MOTS-c, semax and epitalon, each by three votes or fewer, and rejected emideltide. Our report on the July votes gives each count.

One detail illustrates how the process runs independently of its nominators. FDA's briefing document records that several nominations for these substances had been withdrawn by their nominators, and that FDA elected to proceed with presenting the substances to the committee anyway (FDA briefing document) ⁷. Once a substance is in the process, the agency decides whether to finish evaluating it.

As of October 4, 2026, FDA has not proposed a rule adding any of the six, and none has been moved into Category 1. Step 5 has not started. Until it finishes, no pharmacy has a lawful route to compound them, which our BPC-157 prescription article tracks for the most-searched of the six.

What happens when FDA says no

A substance can also be written into the regulation as excluded. Part (b) of 21 CFR 216.23 names oxitriptan, piracetam, mild silver protein and tranilast as substances FDA decided, after balancing the four criteria, will not be on the list (regulation) ². A pharmacy cannot rely on the list for them, and the decision stands until FDA changes the regulation.

A decision is not necessarily permanent. FDA has said that anyone may petition it to amend the list, to add or delete substances or to consider information different from what it presented to the committee, using its general citizen-petition procedure (proposed rule) ⁴. In practice, overturning an exclusion means bringing new evidence on the same four criteria that led to it.

For the 2026 peptides, emideltide is the closest case: the committee agreed with FDA staff that it should not be listed. If FDA follows that advice in a rule, emideltide could join the excluded substances in part (b), rather than simply remaining unlisted, which would make a later reversal depend on a petition with new evidence.

What listing would and would not change

If FDA did add a peptide to the list, a licensed pharmacist could compound it for an individual patient on a valid prescription, under the rest of section 503A's conditions. That would be a real change from today. It would not make the peptide approved, establish a dose, or show it works; the regulation's own warning says listed substances lack adequate evidence of safety or effectiveness (regulation) ². It would also do nothing for 'research use only' products, which sit outside compounding entirely.

It would not apply to 503B outsourcing facilities either, which have a separate bulks list with its own process.

How long it takes

The process has no fixed timetable. The docket opened in 2015, the first final rule came in 2019 with six substances, and the 2019 proposal for five more has not become final as of the current regulation (regulation) ². Committee meetings are scheduled when FDA has evaluations ready, and the gap between a vote and a proposed rule is open-ended. Anyone tracking a substance should watch three places: FDA's interim-policy category lists, the Federal Register for a proposed rule, and the regulation itself at 21 CFR 216.23.

Our regulatory tracker checks those for each peptide and dates every status, and our legal status checker shows where each compound stands today.

Common misreadings

• 'The committee approved BPC-157.' It recommended listing; only FDA rulemaking can list a substance, and listing is not approval.
• 'Removed from Category 2 means pharmacies can compound it.' No. Removal from Category 2 is not Category 1 and not the list.
• 'A substance on the list is FDA-endorsed.' The regulation says the opposite and calls such claims misbranding.
• 'Withdrawing a nomination stops the process.' In 2026 FDA proceeded with substances whose nominations had been withdrawn.

How it adds up (as of October 4, 2026)

A substance with no USP monograph and no approved drug behind it can be compounded under section 503A only if FDA lists it at 21 CFR 216.23. The path runs from a nomination in docket FDA-2015-N-3534, through FDA's evaluation on four criteria and a required consultation with the Pharmacy Compounding Advisory Committee and USP, to a proposed and final rule. The list holds six substances and no peptides. The 2026 cycle reached the committee, which backed six peptides against staff advice, but FDA has not begun the rulemaking that would list any of them.

Frequently asked questions

How does a substance get on the 503A bulks list?

It is nominated in FDA docket FDA-2015-N-3534, evaluated by FDA on four criteria, discussed by the Pharmacy Compounding Advisory Committee, and then added only through a proposed and final rule.

What is on the 503A bulks list?

As of the September 2026 regulation, six substances: Brilliant Blue G and five topical-only agents. No peptides.

Is a PCAC vote binding?

No. The committee advises; FDA decides and must still complete rulemaking to change the list.

Who can nominate a substance?

Any interested group or individual, through the public docket, with information on the substance, its use and supporting literature.

Is BPC-157 on the 503A list?

No. The committee recommended it in July 2026, but as of October 4, 2026 FDA had not proposed a rule to add it.

Related on Grey Peptides

• The July 2026 PCAC votes
• Category 1, 2, 503A and 503B explained
• Can a doctor prescribe BPC-157?
• Regulatory tracker

Sources

1. 21 U.S.C. 353a (Federal Food, Drug, and Cosmetic Act section 503A), subsections (b)(1)(A)(i) and (c); text read October 4, 2026.
2. 21 CFR 216.23, Bulk drug substances that can be used to compound drug products in accordance with section 503A (eCFR, version current September 1, 2026; added at 84 FR 4710, February 19, 2019); read October 4, 2026.
3. Food and Drug Administration. List of Bulk Drug Substances That Can Be Used To Compound Drug Products in Accordance With Section 503A; final rule. 84 FR 4696, February 19, 2019; read October 4, 2026. Source
4. Food and Drug Administration. Amendments to the List of Bulk Drug Substances That Can Be Used to Compound Drug Products in Accordance With Section 503A; proposed rule. Federal Register, September 5, 2019; read October 4, 2026. Source
5. Food and Drug Administration. Bulk Drug Substances That Can Be Used To Compound Drug Products in Accordance With Section 503A; Establishment of a Public Docket. 80 FR 65765, October 27, 2015 (Docket FDA-2015-N-3534); read October 4, 2026. Source
6. Food and Drug Administration. Interim Policy on Compounding Using Bulk Drug Substances Under Section 503A of the Federal Food, Drug, and Cosmetic Act; guidance for industry; read October 4, 2026. Source
7. Food and Drug Administration. Briefing Document, Pharmacy Compounding Advisory Committee meeting, July 23-24, 2026 (Docket FDA-2025-N-6895); read October 4, 2026. Source

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.