Where a Compounded GLP-1's Active Ingredient Is Allowed to Come From

The short answer

Most writing about compounded medicine stops at the pharmacy. The rules do not. Federal law reaches one step further back, to the bulk drug substance the pharmacy starts with, and sets conditions on where that powder came from and what has to travel with it.

Those conditions are not a formality. They are part of what makes the compounding lawful in the first place, and a preparation made from a substance that fails them is not simply lower quality. It falls outside the exemption the pharmacy is relying on.

The conditions also differ depending on which kind of pharmacy is doing the work, and the difference is larger than most people expect.

The three-step test a state-licensed pharmacy applies

A pharmacy compounding under section 503A of the Federal Food, Drug, and Cosmetic Act may only use a bulk drug substance that clears one of three tests, taken in order.

The first is a monograph. If an applicable United States Pharmacopeia or National Formulary monograph exists for the substance, the substance must comply with it, and with the USP chapter on pharmacy compounding. A monograph is a published standard describing what the substance is and how it is identified and tested, so this step outsources the specification to an established reference rather than leaving it to the buyer.

The second applies only if no such monograph exists. In that case the substance must be a component of a drug approved by FDA. The logic is inherited: if the agency has already evaluated that ingredient inside an approved product, the compounder is not starting from nothing.

The third applies only if neither of the first two does. The substance must then appear on a list FDA develops through rulemaking, known as the 503A bulks list. This is the narrow door, and it is narrow on purpose.

Read the order carefully, because it is doing real work. A compounder does not get to choose the most convenient of the three. The steps are conditional on one another, and the third is available only when the first two are genuinely unavailable.

Two conditions that apply whichever step you land on

Two further requirements sit on top of all three, and these are the ones worth knowing as a reader.

The substance must have been manufactured by an establishment registered with FDA under section 510 of the Act. The statute is explicit that a foreign establishment counts, provided it is registered. So the rule is not that the powder has to be made domestically. It is that whoever made it has to be on FDA's register.

The substance must also be accompanied by valid certificates of analysis, one for each bulk drug substance. This is the requirement that most often gets described loosely, so it is worth stating exactly what it covers. The law attaches the certificate to the incoming raw material, and it is the supplier's document about the powder the pharmacy bought.

That is not the same thing as a test of the finished vial that ships to a patient, and the two documents are easy to conflate because both get called a certificate of analysis. A seller offering you a batch document for your own preparation is offering something the bulk-substance rule does not itself require. That can be a genuine courtesy. It is simply a different document from the one the statute is talking about.

FDA's own summary of this area adds a short instruction to compounders that reads like plain advice: know your bulks supplier.

An outsourcing facility faces a different test entirely

A facility registered under section 503B does not work through the monograph ladder for permission to use a substance at all. Its test has two doors, and only two.

The bulk drug substance must appear on a list identifying bulk drug substances for which there is a clinical need, known as the 503B bulks list. Or the drug product compounded from that substance must appear on FDA's drug shortage list at the time of compounding, distribution and dispensing.

Note how tightly the second door is worded. It is not enough for a shortage to have existed when the order was placed. The listing has to hold at compounding, at distribution and at dispensing, which is three separate moments rather than one.

The two conditions from the previous section still apply here. Bulk substances used by an outsourcing facility must also be accompanied by a valid certificate of analysis and must have been manufactured by an establishment registered under section 510. If an applicable USP or National Formulary monograph exists, the substance must comply with it.

This is why the shortage question and the ingredient question are the same question for a 503B facility, and why a change in a shortage listing reaches all the way back to what the facility is permitted to buy.

The interim policy, and why a list is not the whole map

Building the 503A bulks list has taken a long time, and FDA created an interim policy so that evaluation would not disrupt treatment in the meantime. It describes conditions under which the agency does not intend to act against state-licensed pharmacies, federal facilities and licensed physicians compounding from substances that could not otherwise be used. A parallel interim policy exists for outsourcing facilities.

The policy sorts nominated substances into three categories, and the categories carry very different meanings.

Category 1 substances may be eligible for the list, were nominated with enough supporting information for FDA to evaluate them, and do not appear on any other list. FDA does not intend to take action against a compounder for using them, provided the conditions in the guidance are met.

Category 2 is the one to read closely. These substances were also nominated with enough information to evaluate, and may also be eligible for the list. But FDA has identified significant safety risks relating to their use in compounding pending further evaluation, and therefore does not extend the category 1 policy to them. The agency publishes the safety information describing those risks, and says it would consider taking action against a compounder using them under its general enforcement policies.

Category 3 substances may be eligible but were nominated with insufficient supporting information for FDA to evaluate them. An absence of evaluation is not a finding, in either direction.

The practical lesson is that being off a list can mean several unrelated things. It can mean a substance was never nominated, or was nominated too thinly to assess, or was assessed and flagged for safety. Those are not the same situation, and a marketing page that says only that a substance is not prohibited has told you nothing about which one applies.

Two further limits on the finished preparation

The bulk-substance conditions govern the input. Two more conditions govern what may be made from it, and both are in the same section of law.

A compounder may not compound a drug product that appears on a list FDA publishes of drug products withdrawn or removed from the market because they, or components of them, were found unsafe or not effective. That list exists precisely so a withdrawn product cannot quietly reappear through a compounding pharmacy.

A compounder also may not compound regularly or in inordinate amounts any drug products that are essentially copies of a commercially available drug product. The statute carves out one situation: a change made for an identified individual patient that produces for that patient a significant difference, as determined by the prescribing practitioner.

That carve-out is narrow and specific, and it is worth noticing what it requires. A determination by the prescriber, for an identified patient, that the change makes a significant difference for that person. It is not a description of a product line.

What this lets you ask

Ask which entity manufactures the active ingredient, and whether it is registered with FDA under section 510. The question is answerable, and a program that has never considered it will sound like it.

Ask whether the pharmacy compounds under section 503A or as a registered outsourcing facility under section 503B, because the ingredient rules genuinely differ and the answer tells you which set applies.

Ask what document the seller means when it offers a certificate of analysis, and what it covers: the incoming bulk substance, or the finished preparation in your box. Both are real documents. They answer different questions.

A program that can name its pharmacy and describe its supply chain in these terms has told you how it operates. One that responds only that its ingredients are pharmaceutical grade has used a phrase that appears nowhere in the conditions above.