Would you re-test orforglipron after two weeks at 40 °C, or accept the original certificate?

Setup, so nobody has to ask: orforglipron · two weeks · 40 °C.

I am trying to build something sustainable rather than something thorough that I will abandon.

I have already decided the broad direction; this is about the specifics.

What should I decide now, and what should I defer?

two weeks is 14 days, and at 40 °C the ten-degree rule of thumb makes that roughly 158 refrigerated days of equivalent exposure. 40 °C is 35 kelvin above the 5 °C middle of a 2–8 °C refrigerator. The ten-degree rule of thumb — degradation rate roughly doubling per 10 K — makes that about 11 times the refrigerated rate, which is an order-of-magnitude statement and not a shelf life. Compare that against what the certificate covers, which is the material as it left the laboratory on the date of analysis and nothing after it. That is short enough that a re-test is a stability study rather than a safety check — worth doing if you will publish the result, hard to justify if you will only reassure yourself. If you do re-test, send it for content as well as purity; the 14 days will have moved one of them further than the other.

Start from the question: how many vials from this lot do I need to test to claim that the lot meets specification, and the answer depends on both the lot size and the acceptable risk.

Under AQL sampling plans, testing two vials from a fifty-vial lot gives you an operating characteristic curve that tells you what risks you are accepting.

Acceptance Sampling by Attributes defines the number of samples you need from a lot to claim a specified quality level at a specified risk — it is in ANSI standard Z1.4.

Published data on lot homogeneity from manufacturers who sample multiple vials consistently find variation below the published specifications, suggesting the sampling plans work.

Assume segregation is possible, and design your sampling to catch it if it exists.

edited 16 Apr 2026 by esben_lykke — updated for the 2026 guidance change

A certificate that reports one test result on one vial extrapolates to claim that all two hundred vials in the lot are identical, which is an assumption worth questioning.

If the lot was manufactured in multiple batches, testing vials from each batch separately establishes whether batch-to-batch variation is acceptable.

Testing a vial that has been open in the lab for three months is testing aged material, not the fresh lot, and the result should be explicitly noted as a retest.

Sampling plans for pharmaceutical manufacturing are defined in ISO 2859 and ANSI Z1.4, and they are based on statistical sampling theory.

I would treat a "complies with" statement without sampling details as a claim rather than as evidence.

The practical summary: a lot number without a sampling statement is a lot number without meaning.

If a lot has visibly segregated — some vials showing different appearance — then sampling the top and bottom of the shipment is worth doing.

If the entire lot failed qualification, a retest on a different vial is sometimes done, but reporting a retest result under the same lot number is misleading.

It helps to be literal here: for a quantitative result like content, the acceptable range determines how many vials you need to test to establish the lot complies.

Lyophilised peptide homogeneity studies show that vial-to-vial variation is usually small but occasionally large, depending on the distribution in the freeze-dryer.

The caveat is that sampling is a trade-off between cost and confidence, and neither test nor assumption is cost-free.

If testing multiple vials, state how many you tested and why you chose those vials.

Specifically, the failure mode here is publishing a result that applies to the tested vial alone while implying it applies to the entire lot.

A statement that "lot 20260412 complies with specifications" is meaningless without stating which vials from the lot were tested and how many there were.

The ICH Q3A and Q3B thresholds for reporting, identification and qualification of impurities are the framework the pharmaceutical industry works to, and they are worth reading even though nothing in the research-grade supply chain is obliged to meet them, because they tell you which numbers a competent analyst would consider worth reporting at all.

If you only pay for one test, pay for quantified content. Purity is the number everyone quotes and content is the number that changes what you do.

More usefully, two vials tested from a lot of ten is very different from two vials tested from a lot of ten thousand, and most certificates do not state the lot size.

If you have reason to suspect inhomogeneity — different appearance in different vials, or a long or warm shipment — testing more vials is the diagnostic move.

In practice: ask for the chromatogram, check the method section, check the lot number against the vial, and set your accept threshold before you see the result rather than after.