Why does compounded cagrilintide potency vary between pharmacies?

Costs, fees and monitoring all included, I am trying to compare like with like.

I can predict the outcome but I cannot explain it, which means I will get the next case wrong.

I would like to know how confident the field actually is about this.

So what is the mechanism, and how well established is it?

Model the cost across the whole route, including the parts that are not the drug: consultation fees, laboratory monitoring, shipping, and the tests you will pay for yourself.

503A and 503B differ in what they are permitted to do and what they must demonstrate. A 503A pharmacy compounds against individual prescriptions, is exempt from current good manufacturing practice requirements, and is regulated primarily at state level with USP chapter compliance as the operative standard. A 503B outsourcing facility registers federally, must comply with cGMP, may prepare without patient-specific prescriptions, and is subject to FDA inspection. The practical consequence is that a 503B preparation carries release testing and a 503A preparation generally does not.

Features of a defensible telehealth intake: a real history including contraindications and family history, a recorded weight and height rather than a self-attested figure, baseline laboratory work or a documented reason for its absence, a named prescriber you can identify and verify, a titration plan, and a mechanism for reporting adverse events that reaches a clinician. A checkbox intake that issues a prescription in four minutes has none of these.

FDA drug shortage list status is published and is the operative fact for whether compounding a copy of an approved drug is permitted under the relevant statutory exemptions; the status changes, and the change has downstream consequences for supply.

Model twelve months, not one. The fee structures are designed to be compared monthly.

Prior authorisation is an adjudication against written criteria, and the criteria are usually obtainable. Requesting them before submitting is the single highest-yield step in the process.

Denials come in two flavours and it is worth identifying which you have. A criteria denial means the submission did not evidence something the criteria require, and it is fixed by supplying the evidence. A formulary exclusion means the plan does not cover the drug at any level for any indication, and no amount of clinical documentation changes it — the route there is a formulary exception request or an employer-level appeal.

Twelve-month cost modelling, laid out: take the monthly product cost, add consultation or subscription fees, add laboratory monitoring at your chosen interval, add shipping, and then adjust the product cost for actual delivered content and dead-space loss. The route that looks cheapest per vial frequently is not cheapest per twelve months, because the fee structure and the monitoring dominate at lower product costs.

Worth noting that regulatory status in this area has changed repeatedly over the past three years, so any answer including a date should be checked against the current position.

Verify accreditation on the accreditor’s register rather than on the pharmacy’s website. It takes a minute.

edited 14 May 2026 by Dr_Tomas_Kral — added the citation requested in comments

Mechanically, potency variation between compounders is a manufacturing-control question rather than an integrity question, and it is the predictable consequence of preparing a potent peptide by hand at small scale.

What a payer wants in a prior authorisation is documentation mapped to their own written criteria, in their own terms: a diagnosis code, a documented body mass index or comorbidity meeting their threshold, a record of a supervised lifestyle intervention over their specified duration, and documentation of any step-therapy agent tried and its outcome. A clinical narrative that does not map onto those fields will be denied by someone who never reads the narrative.

More usefully, the salt-form point: the statutory pathway for compounding a copy of an approved drug during a shortage applies to the same active moiety as the approved product. A preparation described as a salt form — "semaglutide sodium", "semaglutide acetate" — is describing a different chemical entity from the approved base, and the description is usually there to construct an argument that it is not a copy. Whatever the legal merits, it means what is in the vial is not what was studied.

USP General Chapter <797> on sterile preparation compounding sets the microbiological risk categories and default beyond-use dates that most compounded beyond-use dating in this space derives from.

Keep every document. The appeal you might need in six months is built from records you have to have kept now.

A defensible telehealth encounter has identifiable features, and the absence of those features is the most useful signal available to a prospective patient.

A beyond-use date for a compounded multi-dose preparation is set under USP chapter provisions on the basis of microbiological risk category and, where available, supporting stability data. In practice most beyond-use dates in this space are default values from the risk-category table rather than the output of a stability study, and the two should not be read as equivalent claims.

The limitation of cost modelling is that it assumes a stable price environment, and the price environment in this category has been anything but stable.

If the intake did not ask about contraindications, that tells you what kind of service it is.

It helps to be literal here: the distinction that governs most of this is between a preparation made for an identified patient against a prescription and a preparation made in bulk for office stock, and the two sit under different statutory provisions with different testing obligations.

The internal-then-external appeal path is worth pursuing further than most people do, because the external reviewer is not the plan. Internal appeals are adjudicated by the entity that issued the denial; external review is conducted by an independent organisation against the same criteria, and it overturns a non-trivial fraction of denials.

The statutory basis for the 503A/503B distinction is sections 503A and 503B of the US Federal Food, Drug, and Cosmetic Act as amended by the Drug Quality and Security Act of 2013, and the FDA’s guidance documents on each are the authoritative description of what is permitted.

The caveat is jurisdictional. Almost everything in this area is specific to a country and often to a sub-national jurisdiction, and a confident answer that does not name a jurisdiction should be treated as describing somewhere else.

Ask for the written criteria before you submit. Everything else in the process is easier once you have them.