Compounding Pharmacy Regulations: Sections 503A, 503B, and USP Standards

Compounding pharmacies in the United States are regulated under two federal tracks set by the Federal Food, Drug, and Cosmetic Act: Section 503A covers traditional pharmacies that fill patient-specific prescriptions under mostly state oversight, and Section 503B covers outsourcing facilities that compound in larger volumes under direct FDA supervision. Which track applies determines the safety standards a facility must meet, whether it needs a prescription for each preparation, and how widely it can distribute. On top of both tracks, the United States Pharmacopeia sets the technical standards — chapters 795, 797, and 800 — that define how compounded preparations must actually be made.

Why There Are Two Tracks

The current framework comes from the Drug Quality and Security Act, signed in November 2013 after a 2012 fungal meningitis outbreak traced to contaminated steroid injections from the New England Compounding Center in Massachusetts. The outbreak caused 751 infections and 64 deaths across 20 states, and the facility responsible had been operating between traditional pharmacy compounding and large-scale manufacturing without effective oversight from either state or federal regulators.¹

Title I of the Act amended the Federal Food, Drug, and Cosmetic Act to sort every compounder into one of two defined categories. Section 503A sets conditions under which traditional pharmacies can compound without meeting full FDA drug-approval requirements. Section 503B creates a voluntary registration pathway for outsourcing facilities that accept stricter federal oversight in exchange for broader distribution rights.¹

Section 503A: Traditional Compounding Pharmacies

A pharmacy that meets Section 503A conditions is exempt from three major FDA requirements: current good manufacturing practice (cGMP) rules, labeling with adequate directions for use, and new drug approval.² Those exemptions come with tight restrictions on what the pharmacy can do.

Every compounded drug must be prepared for an identified individual patient based on a valid prescription. A pharmacist or physician may compound limited quantities in advance, but only where there is an established history of prescriptions for that specific patient or from that specific prescriber.³ A 503A pharmacy cannot compound for general “office use” — stocking a clinic’s shelves with pre-made doses that have no patient names attached. Prescribers who need compounded drugs on hand for immediate administration have to source them from a 503B facility instead.

Section 503A also prohibits pharmacies from regularly compounding drugs that are essentially copies of commercially available products.³ The point is to keep compounding focused on genuine gaps, like a pediatric liquid version of an adult tablet or a dye-free formulation for a patient with an allergy, rather than competing with approved manufacturers.

State Boards of Pharmacy do the primary regulating: they license pharmacists, inspect premises, and enforce professional conduct standards. The FDA cooperates with the states and keeps jurisdiction to act when pharmacy activities violate federal law, but routine oversight stays with the state.²

Interstate Distribution Limits

Section 503A caps how much a pharmacy can ship across state lines. If the state has signed a Memorandum of Understanding with the FDA covering interstate distribution and complaint investigations, the MOU’s terms apply. If the state has not signed, the pharmacy is limited to no more than five percent of its total prescription orders going out of state.³

The rule is currently in flux. The FDA issued a standard MOU in October 2020, but several compounding pharmacies challenged it in federal court. The U.S. District Court for the District of Columbia remanded the MOU to the FDA and required the agency to either certify no significant effect on small businesses or prepare a regulatory flexibility analysis. The FDA has said it plans to conduct notice-and-comment rulemaking on the interstate distribution provisions to complete that analysis. Until then, the five-percent cap remains the default for states without an agreement.⁴

Section 503B: Outsourcing Facilities

A compounder that wants to supply hospitals, clinics, and physician offices with ready-to-use stock can voluntarily register with the FDA as an outsourcing facility. Registration allows compounding without patient-specific prescriptions and broad interstate distribution, but it brings direct federal oversight that is far more intensive than what 503A pharmacies face.⁵

The biggest practical difference is that 503B facilities must comply with current good manufacturing practice requirements. Section 503B does not exempt them the way 503A exempts traditional pharmacies. That means validated processes, documented procedures, and rigorous testing on the same footing as conventional pharmaceutical manufacturers. The FDA inspects outsourcing facilities on a risk-based schedule set by the agency, with no small-operation exemptions.⁵

Ingredient Restrictions

Bulk drug substances are only permitted if they appear on an FDA-established list identifying substances for which there is a clinical need, or if the finished drug is on the FDA’s current drug shortage list. Any drug the FDA has withdrawn or removed from the market for safety or efficacy reasons is off-limits entirely.⁵

Annual Fees

Outsourcing facilities pay annual establishment fees to keep their registration active. For fiscal year 2026 (October 2025 through September 2026):

Qualified small business: $6,829 per year
All other facilities: $20,726 per year
Reinspection fee: $20,486, with no small-business discount

The reinspection fee applies when the FDA has to return after identifying problems during a prior inspection.⁶ These are separate from any state licensing costs.

Compounding During Shortages

Outsourcing facilities generally cannot make drugs that are essentially copies of FDA-approved products, but that restriction lifts when the approved drug is on the FDA’s official drug shortage list. While a drug is listed, a 503B facility can compound identical or nearly identical copies and can use bulk drug substances to do so.⁷

Once the drug comes off the list, there is a limited wind-down. Orders already received while the drug was in shortage can still be filled, but the FDA may take enforcement action if a facility keeps filling new orders after removal, or continues filling existing orders more than 60 days after removal.⁷

USP Standards That Apply to Both Tracks

The United States Pharmacopeia publishes the technical standards that turn regulatory requirements into specific, measurable procedures. Whether a facility operates under 503A or 503B, USP chapters define the baseline for safe preparation.

USP Chapter 795 covers non-sterile compounding: oral liquids, creams, ointments, and capsules. It addresses ingredient selection, equipment, quality checks, and beyond-use dates that specify how long a compounded product remains stable and safe. Beyond-use dating depends on the ingredients’ chemistry and the potential for microbial growth, and it is not the same as the expiration dating used on manufactured drugs.

USP Chapter 797, official as of November 1, 2023, applies to sterile compounding: injectables, IV solutions, and ophthalmic preparations. It requires classified cleanroom environments with ISO-rated air quality through HEPA filtration, detailed garbing and hand hygiene procedures, environmental monitoring, personnel competency testing, and risk-based beyond-use dating.

USP Chapter 800 governs handling of hazardous drugs, mainly certain chemotherapy agents, hormones, and antivirals. It requires containment engineering controls — a primary containment device such as a Class II biological safety cabinet, sitting inside a dedicated negative-pressure room with HEPA-filtered air changes, separate storage for hazardous drugs, and impervious surfaces with coved wall junctures. Facilities have to monitor and record pressure differentials daily to confirm containment.⁸ Retrofitting an existing pharmacy to meet USP 800 often requires significant construction.

Adverse Event Reporting and Inspections

Outsourcing facilities must report any adverse drug experience that is both serious and unexpected to the FDA as soon as possible, and no later than 15 calendar days after first receiving the information. The report has to include a copy of the drug’s current labeling. Failing to submit is a prohibited act under the Federal Food, Drug, and Cosmetic Act and can trigger enforcement on its own.⁹ Traditional 503A pharmacies are not subject to this specific federal reporting requirement, though state boards may impose their own.

Patients and providers who experience problems with a compounded drug from either type of facility can report to the FDA through the MedWatch program.¹⁰

When FDA inspectors observe violations at an outsourcing facility, they document them on a Form 483, presented to management at the close of the inspection. The FDA recommends a written response within 15 business days. For observations too complex to fully address in that window, the agency expects at least a corrective and preventive action plan with a proposed timeline, submitted in the same 15-day period. The FDA does not ordinarily hold back regulatory action for responses received more than 15 business days after the 483 was issued.¹¹ Inadequate or missing responses typically escalate to a Warning Letter, and continued non-compliance can lead to recalls, injunctions, or loss of registration.

Veterinary Compounding Is a Separate Framework

Sections 503A and 503B apply only to human drugs. Compounding for animals is governed instead by the FDA’s enforcement discretion policies under Guidance for Industry #256. Technically, compounding an animal drug from bulk drug substances produces an unapproved “new animal drug” that violates federal law, but the FDA generally will not take enforcement action when specific conditions are met. Enforcement discretion currently extends to compounding for nonfood-producing animals, antidotes for food-producing animals, and sedatives or anesthetics for free-ranging wildlife, and the guidance applies to veterinarians, state-licensed pharmacies, and federal facilities.¹² If you are researching rules for a compounded animal medication, the 503A/503B framework is not where to look.

1
Hospital Pharmacy. The Drug Quality and Security Act
2
Food and Drug Administration. Pharmacy Compounding of Human Drug Products Under Section 503A of the Federal Food, Drug, and Cosmetic Act Guidance
3
U.S. Food and Drug Administration. Section 503A of the Federal Food, Drug, and Cosmetic Act
4
U.S. Food and Drug Administration. Compounding Information for States
5
Office of the Law Revision Counsel. 21 USC 353b – Outsourcing Facilities
6
Federal Register. Outsourcing Facility Fee Rates for Fiscal Year 2026
7
U.S. Food and Drug Administration. Compounding when Drugs are on FDAs Drug Shortages List
8
American Society for Health Care Engineering (ASHE). Physical Environment Provisions of USP 800 Hazardous Drugs – Handling in Healthcare Settings
9
Food and Drug Administration. Adverse Event Reporting for Outsourcing Facilities Under Section 503B of the Federal Food, Drug, and Cosmetic Act
10
U.S. Food and Drug Administration. Compounding Risk Alerts
11
Food and Drug Administration. Responding to FDA Form 483 Observations at the Conclusion of a Drug CGMP Inspection
12
U.S. Food and Drug Administration. CVM GFI 256 – Compounding Animal Drugs from Bulk Drug Substances