The 503A bulks list, explained

A pharmacy that compounds a drug for an individual patient works under section 503A of the Federal Food, Drug, and Cosmetic Act. Section 503A exempts that pharmacy from three things a drug maker must do: get FDA approval (section 505), carry full directions for use on the label (section 502(f)(1)), and follow current good manufacturing practice (section 501(a)(2)(B)). In exchange, the pharmacy has to meet conditions. One of them is about the raw ingredient, the "bulk drug substance".

Three ways an ingredient qualifies

Under section 503A(b)(1)(A)(i), a bulk drug substance may be used if it:

• meets an applicable United States Pharmacopeia or National Formulary monograph, if one exists, and the USP chapter on compounding; or
• is a component of an FDA-approved drug, if no monograph exists; or
• appears on a list FDA develops by regulation: the 503A bulks list.

Most peptides discussed online have no USP monograph and are not part of any approved drug. For them, the third route is the only one. That is why the list matters so much to the peptide debate. Approved peptide drugs such as semaglutide or tesamorelin take the second route, which brings its own limits on copying approved products (see GLP-1 compounding policy).

How FDA decides

FDA set the rules in a final rule published on 19 February 2019 (84 FR 4696). It evaluates four criteria and balances them substance by substance:

The 2019 rule placed six substances on the list, all non-peptides and most for topical use only, and declined four. A proposed rule in September 2019 would add five more and decline 26. The list grows slowly because every addition needs its own rulemaking.

The interim categories

Because the list is incomplete, FDA runs an interim policy while it works through nominations. The current guidance was finalised on 7 January 2025 (90 FR 1136), replacing a 2017 version. It sorts nominated substances into three categories:

Substances that were in Category 2 but whose nominations were withdrawn are listed separately by FDA. They are in none of the three categories. The Category 2 page goes through them one by one.

What being on the list does, in FDA's words

At the July 2026 committee meeting, Matthew Lash, acting director of FDA's Office of Compounding Quality and Compliance, set out what follows when a substance is placed on the 503A list. His slide said the compounded product "is not FDA approved"; that a 503A product "is not required to have a label to inform patients and providers how to use it"; that it is not required to comply with good manufacturing practice, though the ban on insanitary conditions still applies; that 503A compounders "are not required to report adverse events" to FDA; and that, unless the listing says otherwise, the substance "can be compounded for any use or via any route of administration".

The last point is the one most often missed. FDA reviews a substance for specific proposed uses. BPC-157 was evaluated for ulcerative colitis, MOTS-c for obesity and osteoporosis. A listing without limits would not be tied to those uses.

Why the salt form matters

Russell Wesdyk of FDA's Office of Pharmaceutical Quality told the committee that FDA treats each salt, ester and free base as a distinct bulk drug substance. "When FDA places a BDS on the 503A Bulks List through rulemaking, and a salt or ester of an active moiety is listed, only that particular salt or ester may be used." This is why the July 2026 questions asked separately about, for example, "BPC-157 (free base)" and "BPC-157 acetate". It is also why FDA staff raised the problem of common or company names without an official United States Adopted Name: in Wesdyk's words, "it's not clear what is being nominated, compounded, or what substance patients are being dosed with."

How 503B is different

Outsourcing facilities registered under section 503B can make larger batches without patient-specific prescriptions, but they must follow good manufacturing practice and report adverse events. Their bulk ingredients come from a different list, the 503B "clinical need" list, or from drugs on FDA's shortage list. The 503B process runs through Federal Register notices rather than the PCAC route used for 503A. In May 2026 FDA used it to propose keeping semaglutide, tirzepatide and liraglutide off the 503B list.

From nomination to listing

1. Someone nominates a substance, usually a pharmacy, a trade group or a clinic network.
2. FDA's Office of Compounding Quality and Compliance, Office of New Drugs and Office of Pharmaceutical Quality review it against the four criteria.
3. FDA presents its evaluation to the PCAC, which votes. The vote is advisory.
4. FDA publishes a proposed rule, takes comments, and publishes a final rule. Only then is the substance on the list.

A nomination can be withdrawn at any point. FDA has chosen to present withdrawn nominations to the committee anyway: its December 2024 and July 2026 briefing documents both note that a nomination "was withdrawn by the nominator" and that "FDA is electing to proceed".

State boards of pharmacy remain the day-to-day regulators of 503A pharmacies. FDA's own slide put it plainly: compounded products "under 503A are primarily overseen by state regulators". The state laws page covers what states have done. For the words themselves, the compounded glossary entry is a short primer.

Rules change faster than most people's records. If you are on a prescribed peptide, the dose log keeps each dose with the product, the pharmacy and the concentration, and bloodwork sits on the same timeline, so a change of product or source is easier to plan with your prescriber. The peptide library grades how much research exists behind each compound, and that grading does not move when a committee votes. The app is on iOS and Android.