What makes a compounded drug's potency test result out of specification?

A potency or assay result is out of specification when it falls outside the acceptance range the compounder set for that preparation under USP or , or outside a range an applicable monograph establishes. The result does not need to show patient harm, only that the finished preparation's measured strength fell outside the limit the pharmacy had to test against before dispensing it.

Does a compounding pharmacy have to notify prescribers after a potency failure?

When a dispensed lot later tests out of specification, FDA and Missouri's board of pharmacy expect notice to the prescribers who received it, and to patients where the result could cause harm. Missouri's compounding rule writes that notice directly into its recall requirement. A pharmacy's own written quality procedure can create the same duty even where no statute names it by itself.

Can one potency failure lead to a state board or FDA investigation?

A single out-of-specification result rarely draws scrutiny by itself. FDA's 2026 warning letter to Boothwyn Pharmacy shows what happens when a pattern goes uninvestigated: inspectors reviewed 23 OOS investigation reports, nineteen of them still open at the time of the inspection, and built the agency's findings around that pattern rather than any one failed lot.

Potency Testing Failures and Out-of-Specification Results for Compounders

A finished-preparation assay that comes back outside its own acceptance range does not stay a laboratory problem for long. USP <795>'s quality control chapter requires a compounder to investigate any discrepancy in a finished preparation before it is dispensed to the patient. FDA's January 16, 2026 warning letter to Boothwyn Pharmacy, LLC shows what an unexamined pattern of failures looks like from the inspector's side of the table: between July 2024 and May 2025, the firm distributed drug products intended to be sterile that produced 9 lots with sterility failures and approximately 25 lots with potency failures, including a semaglutide injection released at 79.876 percent of its labeled strength and a tirzepatide injection at 86.779 percent.

Quarantine and the Out-of-Specification Investigation

An assay result is out of specification once it falls outside the range the compounder set for that preparation, and USP <795> treats the finding as a discrepancy the compounder must investigate rather than assume away. Where that duty runs depends on which side of the 503A/503B line the pharmacy sits on: an outsourcing facility is subject to the cGMP requirements in 21 CFR parts 210 and 211, including the quality assurance activities built around Section 211.192, while a 503A pharmacy compounding under a patient-specific prescription answers to its state board and to USP instead, with USP 797/800 covering the sterile-compounding version of the same quality control duty. Defending either posture sits inside the same compounding pharmacy defense practice that later handles the 483 response or the recall. FDA's inspectors at Boothwyn reviewed 23 OOS investigation reports and found that 19 remained open at the time of the inspection, with none documenting an attempt to reach an affected patient.

Notifying Prescribers Before the Board Does

A lot that already reached a patient by the time its assay result comes back raises a second question beyond the investigation itself: who gets told, and when. Boothwyn's own standard operating procedure required notifying patients and prescribers once a product's strength, sterility or potency was compromised, and FDA's letter found the firm's response did not address that failure at all. A beyond-use date assumes the labeled strength held for the life of the preparation; once an assay result shows it did not, the notice obligation attaches to every prescriber who received that lot, not only to the next one compounded.

The Recall Decision

A confirmed subpotent or superpotent result can make a lot adulterated, and a state board can write the recall trigger directly into its compounding rule. Missouri's compounding standard requires the pharmacy to notify the prescriber of the nature of the recall and the problem identified, extend that notice to patients if the preparation could cause harm, and report the recall to the board in writing within three business days. Boothwyn initiated its own recall of all in-expiry product carrying an OOS result on July 9, 2025, roughly a month after its inspection closed.

What the Inspection Record Shows

FDA's letter treats the gap between Boothwyn's written OOS procedure and what its records actually showed as the core violation, not any single failed lot. Section 501(a)(2)(A) of the Federal Food, Drug, and Cosmetic Act covers insanitary conditions and applies regardless of whether the pharmacy otherwise meets the conditions of 503A, and an open OOS file is exactly the kind of record scrutinized during an FDA Inspection of a Compounding Pharmacy: Scope, Records and Refusals. The same gap separates an FDA Form 483 Observations: The 15-Day Response from an FDA Form 483 Versus Warning Letter: What Each Means for a compounder with unresolved potency failures already on file.

A pharmacy's own written quality procedure becomes the standard investigators measure the pharmacy against once a lot fails.

Health Law Alliance's attorneys have overseen 2,000+ audits and handled 5,000+ matters, with 25+ years of experience.

It is critical that compounding pharmacies promptly retain experienced healthcare defense counsel once a finished-preparation result comes back out of specification. Early legal intervention can protect the pharmacy's rights, shape how the investigation and any recall notice get documented, avoid inadvertent admissions in a 483 response, preserve relevant defenses, and allow counsel to communicate with FDA or the state board on the pharmacy's behalf. Delaying legal representation can significantly affect the outcome of a matter and expose the pharmacy to unnecessary risk.

Health Law Alliance's 503A compounding pharmacy defense team represents compounders through the full life of a potency or assay failure, from the laboratory investigation and prescriber notice through any state board referral or FDA warning letter. If a finished-preparation test result has come back out of specification, contact us today for a free consultation.