503A vs 503B: Prescription, Office Use, Labels and CGMP Compared

By Benn Bluestein-Veyra, M.Sc. Organic Chemistry · Updated 7 November 2026

The difference between 503A and 503B comes down to one question: is the preparation made for an identified individual patient on a valid prescription, or is it made as stock? Section 503A of the Federal Food, Drug, and Cosmetic Act exempts a drug "compounded for an identified individual patient based on the receipt of a valid prescription order" by a licensed pharmacist or physician.^[1] Section 503B exempts a drug compounded in a registered outsourcing facility, and it is the only one of the two that contemplates dispensing "other than pursuant to a prescription for an individual identified patient", for which the label must carry the statement "Office Use Only".^[2]

Both sections were shaped by the Drug Quality and Security Act of 2013, Public Law 113-54, which Congress passed after the 2012 fungal meningitis outbreak traced to a single compounding pharmacy.^[1][2] The outbreak investigation reported 749 cases of infection across twenty states and 61 deaths, and the 2013 statute created the outsourcing facility category in response.^[3][4]

The comparison table

The table summarizes the statutory conditions in 21 U.S.C. 353a and 353b and FDA’s stated division of oversight.^[1][2][5] The sections that follow give the source language for each row.

A prescription is the condition for 503A; office use is a 503B concept

Section 503A opens by naming the patient. The exemption applies to a drug product "compounded for an identified individual patient based on the receipt of a valid prescription order or a notation, approved by the prescribing practitioner, on the prescription order that a compounded product is necessary for the identified patient".^[1] The same subsection allows compounding "in limited quantities before the receipt of a valid prescription order", but only where that is "based on a history of the licensed pharmacist or licensed physician receiving valid prescription orders" generated within an established relationship with the patient or the prescriber.^[1] FDA’s guidance on the prescription requirement, docket FDA-2016-D-0269, sets out the agency’s policy on these prescription conditions for compounding for identified individual patients.^[6]

Section 503B is written the other way around. Its definitions state that "An outsourcing facility may or may not obtain prescriptions for identified individual patients", and its labeling paragraph requires the statement "Office Use Only" whenever the drug "is dispensed or distributed other than pursuant to a prescription for an individual identified patient".^[2] A practice that wants vials on the shelf for in-office administration is, in federal terms, describing a 503B product or an FDA-approved product, and the published outbreak literature explains why Congress drew the line there: non-patient-specific compounding of sterile preparations was the most common practice behind the outbreaks reviewed by the Centers for Disease Control and Prevention for 2001 to 2013.^[7]

State boards oversee 503A pharmacies; FDA oversees 503B facilities

FDA states the division directly: "Generally, state boards of pharmacy have primary responsibility for the day-to-day oversight of state-licensed pharmacies that are not registered with FDA as outsourcing facilities. FDA does conduct surveillance and for-cause inspections of state-licensed pharmacies that are not registered as outsourcing facilities."^[5] Outsourcing facilities "are primarily overseen by FDA and inspected by FDA according to a risk-based schedule".^[5] The statute lists the risk factors that set that schedule, including compliance history, recall history, the inherent risk of the drugs compounded, and whether the facility has been inspected within the last four years.^[2]

FDA’s inspections page lists 503A and 503B facilities with their Form 483s, warning letters, state referral letters and recalls (updated 22 October 2026 as read for this page).^[8] A 2026 analysis of 48 outsourcing facilities newly registered between January 2020 and April 2025 found that 11 had been inspected by the study cutoff, with an average interval of 2.2 years from registration to first inspection, and that every inspected facility had at least two significant objectionable findings.^[9] Registration therefore tells a buyer that a facility has accepted CGMP obligations and FDA jurisdiction; it does not tell the buyer that the facility has been inspected, and the registered facility table records the inspection date and outcome for each entry.^[10]

USP chapters govern 503A; CGMP governs 503B

Section 503A exempts a compounded drug from section 501(a)(2)(B) of the Act, which is the CGMP provision, and instead requires that bulk substances "comply with the standards of an applicable United States Pharmacopoeia or National Formulary monograph, if a monograph exists, and the United States Pharmacopoeia chapter on pharmacy compounding".^[1] The USP chapters on nonsterile and sterile compounding reach a 503A pharmacy through that statutory reference and through state board rules that adopt them. FDA puts the quality contrast plainly: drugs compounded in outsourcing facilities "are subject to current good manufacturing practice (CGMP) requirements. By contrast, drugs compounded by a licensed pharmacist in a state-licensed pharmacy or federal facility, or by a physician, in accordance with the conditions of section 503A of the FD&C Act, are not."^[5]

Section 503B grants exemptions from section 502(f)(1) (adequate directions for use), section 505 (new drug approval) and section 582 (supply chain security), and leaves section 501(a)(2)(B) in place, so CGMP applies to every outsourcing facility.^[2] FDA’s guidance on how it intends to apply the CGMP regulations to outsourcing facilities is a revised draft under docket FDA-2014-D-0779, and the agency describes it as reflecting "how CGMP requirements should be applied in light of the size and scope of an outsourcing facility’s operations".^[11] The compounding literature gives this CGMP exemption as the structural reason quality testing varies across 503A preparations.^[12]

Bulk substances follow two different lists

A 503A compounder may use a bulk drug substance only if it has a USP or NF monograph, is a component of an FDA-approved drug, or appears on the 503A bulks list that FDA develops by rulemaking, and in every case the substance must come from an establishment registered with FDA under section 510 with a valid certificate of analysis.^[1][13] The sibling page on the 503A bulks list and its categories sets out the codified list, the interim categories and the 2026 peptide changes in detail. A 503B facility may use a bulk substance only if it appears on the 503B bulks list, which FDA builds around "clinical need", or if the compounded drug is on the drug shortage list at the time of compounding, distribution and dispensing.^[2][14] As of 7 November 2026 the 503B list page, last updated 21 August 2023, names five substances for which FDA found a clinical need, all for topical or oral use, and 22 substances for which it did not.^[14]

Labels and adverse event reports are statutory on the 503B side

Section 503B(a)(10) prescribes the label. It must include "the statement ‘This is a compounded drug.’ or a reasonable comparable alternative statement", the name, address and phone number of the outsourcing facility, the lot or batch number, the established name, dosage form and strength, the quantity, the date compounded, the expiration date, storage and handling instructions, the National Drug Code if available, "the statement ‘Not for resale’", and, for drugs not dispensed on a patient prescription, "Office Use Only", together with a list of active and inactive ingredients.^[2] The container must carry the MedWatch web address and telephone number "to facilitate adverse event reporting", and outsourcing facilities "shall submit adverse event reports to the Secretary" in the content and format of 21 CFR 310.305.^[2]

Section 503A contains no corresponding label or adverse event paragraph. A 503A label follows state pharmacy law, and the exemption from section 502(f)(1) means the federal adequate-directions requirement does not apply to the prescription label.^[1] For a practice, the visible result is simple: a vial from an outsourcing facility carries a facility name, a lot and a compounded-drug statement, while a 503A dispensing label carries the patient’s name and the prescriber’s.

Interstate shipping turns on the MOU for 503A and on the wholesaling ban for 503B

A 503A drug qualifies for the exemption only if it is compounded in a state that has signed a memorandum of understanding with FDA addressing "the distribution of inordinate amounts of compounded drug products interstate", or, in a state that has not, if the compounder ships out of state "in quantities that do not exceed 5 percent of the total prescription orders dispensed or distributed".^[1] FDA published a standard MOU in October 2020, was sued, and after a 2021 remand announced notice-and-comment rulemaking; it describes the 2020 MOU as "suspended" and states that it does not intend to enforce the 5 percent limit until a final rule takes effect and an updated MOU is published.^[15] As of 7 November 2026 that remains the live position on FDA’s MOU page.^[15]

Section 503B has no distribution percentage. Its constraint runs the other way: the drug "will not be sold or transferred by an entity other than the outsourcing facility that compounded such drug", which the statute expressly says "does not prohibit administration of a drug in a health care setting or dispensing a drug pursuant to a prescription".^[2] A practice may buy from an outsourcing facility in another state for administration in its own office; it may not resell what it bought. The health-system demand this created, and the uncertainty the unfinished 503B bulks list introduced, are described in the sector commentary.^[16]

Which route fits a patient-specific peptide or hormone order

A prescription written for a named patient, for a strength, combination or dosage form that an approved product does not supply, is the case section 503A was written for, and the statute’s own definition of "essentially a copy" turns on "a change, made for an identified individual patient, which produces for that patient a significant difference, as determined by the prescribing practitioner".^[1] ExaVeyra’s compounded preparations reach a practice this way, through a licensed 503A pharmacy partner on patient-specific prescriptions, with a certificate of analysis available for each lot.^[13]

Stock for in-office administration without a prescription in hand is the case section 503B was written for, or an FDA-approved product. A practice choosing an outsourcing facility can check FDA’s weekly updated registered facility table for the entry’s registration dates, last inspection and any Form 483 or recall; as of 7 November 2026 the 29 October 2026 update listed roughly one hundred facilities.^[10]

• Patient-specific peptide or hormone prescription: section 503A; the practice holds the prescription and the dispensing record, and may request the lot’s certificate of analysis.^[1][13]
• Office stock for in-office administration: section 503B or an approved product; the practice holds the invoice, the lot and the "Office Use Only" label.^[2]
• Either route: the bulk substance came from a registered establishment with a valid certificate of analysis, and the drug is not on the withdrawn list in 21 CFR 216.24.^[1][2]

The controlled-substance overlay applies on both routes

Neither section 503A nor section 503B displaces the Controlled Substances Act. When a compounded preparation contains a scheduled substance, the dispensing pharmacy or outsourcing facility acts under its own DEA registration, and the prescription for a controlled substance must still be issued for a legitimate medical purpose by a practitioner acting in the usual course of practice, which in the compounding context means a patient-specific order. For ExaVeyra’s supply, the 503A pharmacy partner dispenses any controlled substance under its own DEA registration against a patient-specific prescription, and the practitioner decides the mode of evaluation.

This article summarizes publicly available federal regulation for licensed practitioner education. It is not legal advice, medical advice, or regulatory guidance, and it does not establish that any particular product or practice is compliant. Confirm current federal and state obligations with qualified counsel.