Compounding Pharmacy Glossary: 503A, PCAB, USP and More Explained

Compounding pharmacy discussion is dense with acronyms, and the distinctions between them carry real weight — the difference between a 503A and a 503B facility, or between USP 795 and 797, determines what a pharmacy can legally make and to what standard.

This is a reference page. Terms are grouped by what they govern rather than alphabetically, because they make more sense that way.

Facility Types

503A

The section of the Federal Food, Drug, and Cosmetic Act covering traditional compounding pharmacies. A 503A pharmacy compounds preparations against a prescription for an individual, identified patient. It is licensed by state boards of pharmacy and is exempt from certain FDA requirements — including new drug approval and cGMP manufacturing standards — provided it operates within the section's conditions.

503B

The section covering outsourcing facilities, created by the Drug Quality and Security Act of 2013 following the 2012 New England Compounding Center meningitis outbreak. A 503B facility may compound in larger batches without patient-specific prescriptions, but must register with the FDA, comply with cGMP, and submit to FDA inspection. They typically supply clinics, surgical centers, and hospitals.

Our detailed comparison of 503A and 503B compounding pharmacies covers the practical differences.

DQSA

The Drug Quality and Security Act of 2013 — the legislation that created the 503B category and clarified 503A's boundaries.

Quality Standards

USP

The United States Pharmacopeia, a non-profit that establishes standards for drug quality, purity, and strength. Its chapters are referenced in federal law and adopted by state boards, which makes compliance enforceable rather than voluntary.

USP 795

The chapter governing non-sterile compounding — capsules, creams, ointments, oral liquids, troches. Covers facilities, personnel training, ingredient selection, and beyond-use dating.

USP 797

The chapter governing sterile compounding — injectables, ophthalmics, and anything administered by a route requiring sterility. Covers clean-room classification, air quality, environmental monitoring, personnel garbing and validation, and sterility testing.

This is the chapter that matters most for injectable peptides. A pharmacy compounding sterile preparations without USP 797 compliance is producing something that should not be injected.

USP 800

The chapter governing handling of hazardous drugs, protecting personnel and preventing cross-contamination. Relevant to chemotherapy agents and certain hormones.

Our overview of USP 795, 797, and 800 standards covers each in detail.

PCAB

The Pharmacy Compounding Accreditation Board, a division of ACHC. PCAB accreditation is voluntary — a pharmacy chooses to undergo third-party audit against compounding-specific standards. Because it is not required, its presence is a meaningful signal about how a pharmacy chooses to operate. Our list of PCAB-accredited compounding pharmacies covers accredited operations.

cGMP

Current Good Manufacturing Practice — the FDA's manufacturing quality regulations. Required of 503B outsourcing facilities and pharmaceutical manufacturers; not required of 503A pharmacies.

Regulatory Process

Bulks List (503A Bulk Drug Substances List)

The FDA list of bulk drug substances that may be used in 503A compounding where the substance is not a component of an approved drug and has no applicable USP monograph. Substances are evaluated and placed in categories.

This is the mechanism determining which peptides may be compounded, which is why it drives so much of the regulatory news in this space. Our FDA peptide status tracker tracks current standing.

PCAC

The Pharmacy Compounding Advisory Committee, the FDA advisory committee that reviews bulk drug substances and makes recommendations on Bulks List placement. Its recommendations are advisory — the FDA is not bound by them, though it usually follows. Our explainer on what a PCAC meeting is covers the process.

Category 1 / Category 2

Interim categories the FDA uses while evaluating nominated bulk substances. For Category 1 substances, FDA does not currently intend to take action against 503A compounding during evaluation, subject to the other 503A conditions; Category 2 substances have identified safety concerns and generally may not.

Essentially a Copy

A compounded preparation that is essentially a copy of a commercially available drug product. 503A pharmacies generally may not compound these — the significant exception being where a prescriber documents a clinically significant difference for a specific patient, or where the commercial product is on the FDA drug shortage list. This is the concept that governed compounded GLP-1 availability.

Drug Shortage List

The FDA's list of drugs in shortage. Presence on this list permits compounding of preparations that would otherwise be prohibited as essentially a copy — and removal from it ends that permission.

Preparation and Quality Terms

API

Active Pharmaceutical Ingredient — the raw compound providing the therapeutic effect, before formulation.

BUD

Beyond-Use Date — the date after which a compounded preparation should not be used. Distinct from a manufacturer's expiration date, and generally much shorter, because compounded preparations lack the stability testing behind commercial products. Governed by USP 795 and 797.

COA

Certificate of Analysis — documentation from a testing laboratory reporting analytical results for a specific lot: identity, potency, purity, and where applicable sterility and endotoxin levels. A pharmacy willing to provide a COA on request is demonstrating something concrete.

HPLC

High-Performance Liquid Chromatography — the standard analytical method for determining peptide identity and purity.

Endotoxin Testing

Testing for bacterial endotoxins — pyrogenic contaminants that survive sterilization and can cause fever and serious reactions. Required for injectable preparations; sterility alone is not sufficient.

Media Fill

A validation procedure in which a sterile compounding process is performed using growth medium instead of the drug, then incubated to confirm no contamination occurred. Validates the process and the personnel.

Environmental Monitoring

Ongoing air and surface sampling in compounding areas to confirm clean-room conditions are maintained between validations.

Practical Terms

Non-Resident Pharmacy License

The license a pharmacy must hold to ship into a state where it is not physically located. A pharmacy shipping nationwide maintains these across states — verifiable with your state board.

Cold Chain

Temperature-controlled handling and shipping for preparations requiring refrigeration. For peptides this typically means insulated packaging, coolant, and temperature indicators confirming the preparation stayed in range in transit.

Compounding vs Manufacturing

Compounding produces preparations for identified patients against prescriptions. Manufacturing produces drug products at scale for general distribution under FDA approval and cGMP. The line between them is the central regulatory question in this field.

Frequently Asked Questions

What is the difference between 503A and 503B?

503A pharmacies compound against prescriptions for individual identified patients and are state-licensed. 503B outsourcing facilities compound in batches without patient-specific prescriptions, register with the FDA, and must comply with cGMP.

Is PCAB accreditation required?

No. PCAB accreditation is voluntary third-party audit against compounding-specific standards. Because it is optional, choosing to obtain it is a meaningful quality signal.

What does USP 797 cover?

Sterile compounding — clean-room classification, air quality, environmental monitoring, personnel garbing and validation, and sterility testing. It is the essential standard for injectable preparations.

What is the 503A Bulks List?

The FDA list of bulk drug substances usable in 503A compounding where the substance is not part of an approved drug and lacks a USP monograph. It determines which peptides may lawfully be compounded.

What is a beyond-use date?

The date after which a compounded preparation should not be used. It is generally much shorter than a commercial expiration date because compounded preparations lack the stability testing behind approved products.

What does "essentially a copy" mean?

A compounded preparation that duplicates a commercially available drug. 503A pharmacies generally may not compound these, except where a prescriber documents a clinically significant difference for a specific patient, or the commercial product is in shortage.