Potency retest & expiry dating for raw materialsRetest Date vs Expiry Date (ICH Q1A / Q7)

An expiry date is terminal. Past it, the material may not be used, full stop, regardless of what any test shows — it reflects a defined, data-supported point beyond which the manufacturer cannot claim the material still meets specification, typically because degradation is understood to be irreversible, monotonic, and unrehabilitated by mere confirmation of current quality. Finished drug product carries an expiry (shelf-life) date for this reason.

A retest date is different in kind. It marks the point by which a material must be re-examined — re-sampled and re-tested against its full specification, or against the subset of tests relevant to the material's known degradation pathway — before it can be used further. If the material still conforms, it can be released for continued use with a newly assigned retest date (or, per site policy, a defined maximum number of retest cycles or a hard-stop total shelf life). ICH Q7 §11.6 states this directly for APIs: materials held beyond an established period should be tested to confirm continued suitability.

A retest period is not an arbitrary administrative shelf number — it is a statistically derived conclusion from real stability data (long-term storage under labelled conditions, supplemented by accelerated and intermediate conditions per the ICH Q1A(R2) storage-condition matrix), extrapolated per ICH Q1E only as far as the data statistically support.

Requalification is a formal, documented event — not an ad hoc 're-run the assay and see' exercise. A defensible protocol specifies, in advance, what gets tested, how the material is sampled, and what criteria govern the outcome.

1. Sampling — pull from a statistically representative set of containers per the site's sampling plan (not just the top container in the pallet), following the same identity-confirmation steps as an initial receipt sample, since a lot can develop container-to-container heterogeneity over long storage.
2. Test panel — at minimum, potency/assay against specification; for materials known to be moisture-sensitive, a moisture re-check (LOD or Karl Fischer); for materials with known degradation pathways, a targeted impurity/degradation-product panel rather than a full release panel re-run, justified by the material's characterized stability profile.
3. Acceptance criteria — the same specification the material was originally released against, unless a science-based, approved alternative applies (e.g., an impurity limit that only becomes relevant after extended storage and is added specifically for requalification testing).
4. Retest interval assignment — the requalified retest date is typically set using the same interval logic as the original (e.g., another 12 or 24 months) unless site policy or stability data dictate a shorter interval for materials nearing the edge of their overall supported storage duration.
5. Cycle limits — many quality systems cap the number of times a given lot may be requalified (e.g., two extension cycles) or impose an absolute total-storage-time ceiling, because repeated retesting of the same container without evidence the underlying degradation model still holds becomes scientifically indefensible past a certain point.
6. Documentation — the requalification result, the new retest date, and (if changed) the new potency value must be recorded on the lot record with the same rigor as an original CoA disposition, including QA review and approval before the lot re-enters usable inventory.

Most actives do not degrade instantly at a cliff edge; they drift, typically following first-order or pseudo-first-order kinetics for a hydrolytically or oxidatively unstable molecule, or much more slowly and near-linearly for a chemically robust one. The retest date is set at the point where the manufacturer's stability model no longer confidently predicts the material remains within its assay specification without a fresh check.

Whatever the mechanism, the requalification assay result — not the original receipt CoA value — is the number that must drive every subsequent dispense calculation. A material that assayed at 99.8% on receipt and requalifies at 97.1% eighteen months later has a materially different potency factor, and every open recipe consuming that lot needs to reflect the new number, not the stale one.

A supplier's CoA typically states a retest date derived from the supplier's own stability data and labelled storage conditions (temperature, humidity, container/closure system). That date is only valid if the receiving site actually stores the material within those labelled conditions — a material rated for storage at controlled room temperature that spends time in an uncontrolled warehouse corner during a heat event has an unverified basis for its stated retest date, even if the calendar date hasn't been reached yet.

1. Verify the supplier's storage-condition claim matches the site's actual storage location and monitored temperature/humidity history for the full duration the lot has been on hand.
2. Treat any excursion outside labelled storage conditions as a trigger for an out-of-condition assessment — potentially an accelerated requalification — independent of the calendar retest date.
3. Do not extend a supplier-assigned retest date on the strength of the site's own data unless the site has performed (or has access to) stability data specifically supporting that extension; a site cannot unilaterally decide a supplier's material is good for longer without its own scientific basis.
4. Where a material is repackaged into smaller in-house containers, treat the repack as a new event: verify whether the supplier's original retest date and container/closure basis still apply to the new packaging, since a different container can have different moisture/oxygen barrier properties.

Requalification is only complete, from a dispensing-control standpoint, when the new assay value has actually propagated into the potency factor the dispensing system uses — not just filed in the lab's LIMS as a passed result.

1. Lab performs the requalification assay and records the result under the standard result-review/QA-approval workflow, exactly as for an original receipt assay.
2. The lot record's potency factor is recomputed from the new assay value (PF = reference potency ÷ new measured potency, on the correct basis — see potency factor for the anhydrous/as-is/marker/activity conventions).
3. The lot's retest date is updated to the new requalification-derived date, and the prior potency value and retest date are retained in the lot's change history for audit reconstruction.
4. Every open work order or dispense queue item referencing that lot is flagged for the operator/kiosk to recompute the adjusted dispense target using the new potency factor before any further weighing occurs against that lot.
5. If material from the lot was already dispensed under the old potency factor before requalification, that historical transaction is not retroactively altered — the batch record stands as executed — but the deviation/impact assessment for that batch should consider whether the old PF was still within tolerance of the new, requalified value.

The system-level controls that make requalification actually work in practice come down to a small set of blocking rules that must all be enforced consistently.

• Material dispensed after its retest date because the dispensing system only checked the date when the work order was created, not at the moment of weighing.
• Requalification performed and passed, but the potency factor on open work orders was never recomputed, so subsequent batches were charged on the pre-requalification value.
• Repeated requalification of the same lot with no documented scientific basis (no ongoing stability data, no cycle limit) for continuing to extend it.
• A material with a documented storage-condition excursion (temperature/humidity) still released for use on the strength of an unmodified original retest date.
• Repackaged material carrying forward the original supplier retest date with no assessment of whether the new container/closure system supports the same period.
• Retest date and expiry date used interchangeably in SOPs or batch records, leading operators to believe a past-expiry material could be 're-tested back into use.'
• Requalification protocol testing only potency, omitting a moisture or degradation-product check for a material whose known instability mechanism involves more than simple potency loss.