How 503A and 503B Work in California: Shipping Compounded Drugs to a Clinic, Secondary Facilities, and Why 503B Does Not Convert to 503A

The Short Version

Federal law gives compounders two lanes. Section 503A covers a pharmacy compounding for an identified patient on a prescription. Section 503B covers an FDA-registered outsourcing facility that can make larger batches, including stock for clinics to use in the office. California adds its own licenses on top of both, including a license for out-of-state outsourcing facilities that ship into the state. One idea circulates that a 503B product can be turned into a 503A product just for California. That does not work in California or anywhere else. What does exist is a supply model in which a licensed pharmacy buys 503B product and dispenses it, unaltered, on a prescription for a named patient. Here is how the pieces fit, what is allowed, and where the open questions are.

503A and 503B Under Federal Law

• 503A: the patient-specific lane: a drug compounded by a licensed pharmacist or physician, in a state-licensed pharmacy or federal facility, for an identified individual patient on a valid prescription. Limited anticipatory compounding is allowed based on a history of orders. These drugs are exempt from FDA approval, current good manufacturing practice (cGMP) and adequate-directions labeling, and are overseen mainly by state boards. FDA's position is that 503A office stock needs a patient-specific prescription received before the product leaves the pharmacy.
• 503B: the outsourcing-facility lane: a facility that voluntarily registers with FDA as an outsourcing facility and compounds sterile drugs at that address, under a licensed pharmacist. It need not be a licensed pharmacy and may or may not get patient-specific prescriptions. Its drugs are exempt from approval and adequate-directions labeling, but not from cGMP, and FDA inspects on a risk basis. Labels must say the drug is compounded and not for resale, plus Office Use Only when there is no patient prescription.
• The key difference for a clinic: FDA says hospitals, clinics and practitioners can obtain non-patient-specific stock from a 503B outsourcing facility, while 503A pharmacies cannot supply office stock without a patient-specific prescription in hand.

What California Adds

California licenses compounding more tightly than federal law does, and the statute text is in the California Business and Professions Code, which the State Board of Pharmacy publishes in its lawbook.

• Outsourcing facility (BPC 4034 and 4129): California defines an outsourcing facility as an FDA 503B-registered facility doing business within or into California that is licensed by the Board. An FDA-registered outsourcer needs a concurrent California license if it compounds for non-patient-specific distribution within or into California.
• Nonresident outsourcing facility (BPC 4129.2): an out-of-state outsourcer compounding for use in California needs this license. It is renewed annually, is not transferable, requires compliance with the Board's regulations and federal cGMP, and involves a Board inspection at the facility's cost before issuance and at least annually. The Board reviews the facility's compounding policies, recent inspection and accreditation reports, and its list of products reported to FDA. If FDA cancels or suspends the facility's registration, the California license is cancelled by operation of law.
• Sterile compounding pharmacy (BPC 4127): required for any pharmacy compounding sterile drugs, and issued only to a pharmacy that already holds a pharmacy license. A location licensed as a sterile compounding pharmacy cannot also hold an outsourcing facility license (BPC 4129(b)).
• Nonresident sterile compounding pharmacy (BPC 4127.2) and nonresident pharmacy (BPC 4112): an out-of-state pharmacy shipping sterile compounded drugs into California needs the nonresident sterile compounding license, and any out-of-state pharmacy shipping dangerous drugs into the state against a prescription needs a nonresident pharmacy license.
• Scale: Board materials from late 2025 counted 92 FDA-registered outsourcing facilities, of which 3 were California-based and 20 were out-of-state facilities holding a California license.

Office Use vs. Patient-Specific in California

California law lets a pharmacist furnish a reasonable quantity of compounded drug product to a prescriber for office use (BPC 4052(a)(1)). That is state authority, and it does not override FDA's position that 503A office stock is not exempt without a patient-specific prescription. California's own compounding regulations also treat compounding as pursuant to a patient-specific prescription unless the rules say otherwise, with limited anticipatory batches allowed only for identified patient populations with a documented prescription history. Rewritten compounding rules took effect on October 1, 2025. The practical lane for true clinic stock is product from a licensed 503B outsourcing facility, labeled as such. An older California Attorney General opinion read office use broadly, but it construed a predecessor statute and should not be treated as a safe harbor.

What a California Clinic May Do With the Stock

Receiving product is only half of it. California limits what a prescriber may do with drugs once they arrive.

• Prescriber dispensing (BPC 4170): a prescriber may dispense only if the patient is the prescriber's own, the drug is necessary for the condition, the prescriber keeps no pharmacy, labeling and recordkeeping rules are followed, a written prescription is offered, and the patient is told in writing that they may fill it at a pharmacy. Nurse practitioners and physician assistants working under protocol have a narrower hand-over exception for patients of the supervising physician.
• Administering vs. dispensing: using a drug in the office is different from dispensing it, but we did not find a Medical Board or Board of Pharmacy statement that draws the line for med spa stock, so have counsel confirm how your clinic's workflow is characterized.
• Who may order (BPC 4059.5): dangerous drugs may be delivered only to Board-licensed entities, manufacturers, ultimate users, or named prescribers. A management company is not on that list, so the physician or another licensed entity must be the purchaser. An MSO should not buy, hold or resell drug inventory.

The Secondary-Facility Models That Exist

• An out-of-state 503B with a California nonresident license: lawful, with the licensing above. Product shipped to California physicians for office use must carry the 503B labeling.
• A California-licensed 503A pharmacy compounding its own product: dispensed to patients on a prescription for an identified patient, with a sterile compounding license if the pharmacy makes sterile products.
• A licensed pharmacy buying 503B product and dispensing it unaltered: sometimes called the 503B-to-503A model. The pharmacy buys finished product from an outsourcing facility and dispenses it on a patient-specific prescription. FDA's 2023 draft wholesaling guidance (still a draft) treats an outsourcer shipping to a state-licensed pharmacy that dispenses on a prescription as not wholesaling. Secondary analyses say the pharmacy may not alter, split or re-vial the product or pass it to another pharmacy or a physician's office, and the product remains an outsourcing-facility drug throughout, including on its label. We found no California Board statement approving or prohibiting the model, so treat it as an open question for counsel.
• A licensed wholesaler or third-party logistics warehouse: California licenses wholesalers and third-party logistics providers per place of business (BPC 4160 and 4161). FDA's draft says an outsourcer using a licensed 3PL that never takes ownership is generally not wholesaling, while a distributor that buys and resells 503B product is the prohibited model.
• Repackaging: California treats repackaging as manufacturing with narrow pharmacy exceptions, and FDA's position is that repackaged drugs lose the 503A and 503B exemptions. Treat any model that relabels or splits product as high risk.
• Drop-shipping: delivering to a patient requires a prescription for that patient. Delivering to a clinic is office stock and has to come from an outsourcing facility.

Why 503B Does Not Convert to 503A

FDA treats registration as an election. Once a facility registers as an outsourcing facility, its compounding at that facility is 503B, and its drugs are not eligible for the 503A exemptions even if 503A's conditions would otherwise be met. FDA expressly rejects separating the two by a curtain or by time of day. What federal guidance does allow is one owner running a completely separate 503A establishment, with its own rooms, equipment, supplies, entrances and permanent barriers, and labels that clearly say who compounded the drug. California adds that the same location cannot hold both a sterile compounding pharmacy license and an outsourcing license.

• Relabeling office stock as 503A: does not work. A 503A pharmacy needs a prescription for an identified patient before it dispenses.
• Turning unallocated 503B stock into patient-specific orders afterward: is not lawful. The prescription must exist and be valid before dispensing.
• The accurate version: a company can operate a licensed 503B facility, which can also fill patient-specific prescriptions under BPC 4129(e) while meeting pharmacy requirements, and separately a segregated, licensed 503A pharmacy compounding its own patient-specific products. Those are two different establishments with two sets of labels.

GLP-1s in California

Compounded GLP-1s carry their own rules. California's definition of a drug that is essentially a copy of a commercially available product is stricter than FDA's: it requires a pharmacist-documented, clinically significant difference for the identified patient, with a shortage exception. The rewritten rules took effect October 1, 2025, and secondary analysis reads them as aimed at GLP-1 compounders. Federally, FDA declared the tirzepatide and semaglutide shortages over in December 2024 and February 2025, and in April 2026 said neither drug is on the shortage list or the 503B bulks list. FDA proposed on April 30, 2026 to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list, and we did not find a final action. California AB 1990, which would add sourcing, testing and advertising rules for compounded GLP-1s, was reported held in Senate Appropriations in August 2026 and is not law.

What to Ask Your Supplier

• Which licenses do you hold for California?: a California nonresident outsourcing license for office stock, a California pharmacy or nonresident sterile compounding license for patient-specific product, and who the licensed entity is on every label.
• Is each shipment patient-specific or office use?: and does the label say so.
• What exactly is in the product, and where does it come from?: the facility, the bulk substance source and the lot.
• Who is the purchaser and the shipping address?: a licensed physician or entity, never an unlicensed management company.
• What are your recall and adverse-event procedures?: outsourcers licensed in California have short reporting windows.
• Do you ever repackage, split or relabel product?: and if so, under which license.

Claims to Avoid

Do not say that 503B product converts to 503A in California or that the two statuses are interchangeable. Do not call a compounded drug the same as, or generic for, a brand-name drug, or describe it as FDA-approved. Do not brand a compounded drug under the clinic's or the management company's name. Do not promise ready-to-use stock from any compounding pharmacy, claim California licensing is unnecessary, or imply the Board or FDA endorses a product. And do not have the management company purchase, hold or resell inventory.

Sources

• California State Board of Pharmacy: Pharmacy Law lawbook, Business and Professions Code and Title 16 regulations (pharmacy.ca.gov), and Board meeting materials from 2025 and 2026.
• FDA: Guidance on outsourcing facilities and on 503A and 503B (fda.gov), the Compounding and FDA Questions and Answers page, the 2023 draft guidance on wholesaling, and FDA's GLP-1 compounding statements and 2026 bulks-list proposal.
• Federal statute: 21 U.S.C. 353a and 353b (law.cornell.edu).
• Secondary analyses: Pharmacy Times on the 503B-to-503A model, and Frier Levitt on California's essentially-a-copy rules and the return of 503B GLP-1 compounding.

Disclaimer

This article is general educational information, not legal advice. Compounding and pharmacy licensing law is complex and changes, and the right arrangement depends on your specific products, suppliers and clinic structure. Confirm with a California pharmacy and health care regulatory attorney before sourcing or shipping compounded drugs.