Shelf life as a planning constraint

Every lot of drug substance, drug product, and finished product starts losing usable life the day it is made. For a supply planner, that turns inventory into a quantity with a deadline, and the plan has to respect both.

In the United States, each manufacturer’s stability testing program determines a product’s storage conditions and expiration dates¹. The expiry date on the label is fixed, but the shelf life actually available to the plan is shorter, because part of it is spent before a lot can ship and another part is promised to whoever receives it. This article looks at where shelf life goes, how to plan usable inventory by lot and by period, and how to account for retest dates and shelf-life extensions without counting on them too early.

01Shelf life is spent before it is used

A lot’s shelf life starts at manufacture, yet the lot cannot ship until release testing is complete and quality has released it. Packaging, labeling, and transit take more time. At the other end, customers, distributors, markets, and clinical sites often require a minimum remaining shelf life when the product arrives, so the last part of the shelf life is never available to sell.

In this example, a product with a 24-month shelf life has a nine-month window in which it can ship and still arrive with 12 months remaining. Every week of release or transit delay comes out of that window, which is why remaining shelf life has to be checked where the lot will be used, not when it is received into the warehouse.

02Usable inventory is a time-phased number

On-hand quantity tells you how much material you hold. It does not tell you how much of it can still meet demand in a given month. A lot that is fully usable for next month’s shipments may be unusable for orders due in six months, because by then it will no longer meet the remaining shelf life required.

Planning by lot solves this. For every lot and every period, the plan checks whether the lot will still meet the required remaining shelf life when the demand falls due. Once it no longer does, the lot leaves the plan for that demand, and any shortfall appears as a requirement in time to act. Lots are consumed first expiry, first out, so the oldest usable material is used before it ages out, and lots in quarantine or on quality hold stay out of the plan until they are released.

Requirements differ by channel, so the same lot can be usable for one demand and not another. A clinical site may accept a shorter remaining shelf life than a commercial distributor, and markets can set different thresholds. The plan should hold each requirement where it applies, rather than as a single number for the product.

03Batch size sets the write-off risk

Minimum batch and campaign sizes come from equipment, cost, and CDMO terms, and demand rarely fits them neatly. When one batch covers more months of demand than the product’s window to ship, the tail of that batch will expire. In the example above, a batch that covers 20 months of demand against a nine-month window puts more than half of it at risk before it is even made.

The exposure is greatest for low-volume, orphan, and early-launch products, where demand is still building and every batch is large relative to it. Planners can reduce it by comparing months of demand per batch with the window to ship before committing a campaign, splitting campaigns where the economics allow, and timing production so that release lands just ahead of need.

04Retest dates further up the bill of materials

For upstream materials, the date that matters is often a retest date rather than an expiry date. For active pharmaceutical ingredients, the common practice is to assign a retest date², after which the material is re-examined before it can be used. Many companies manage excipients and starting materials the same way under their own procedures.

A retest date is a planning event. If a lot will reach its retest date before it is consumed, the plan needs time and laboratory capacity to retest it, and a fallback in case it does not pass. Carrying retest dates alongside expiry dates at every level of the bill of materials keeps drug substance and raw material plans as dependable as the finished product plan.

05Plan for extensions without counting on them

Shelf life is often extended as real-time stability data accumulates, and that data sets the limit. Under the ICH Q1E guidance in force today, when long-term and accelerated data show little change and little variability, a proposed shelf life can be up to twice the period covered by long-term data, but no more than 12 months beyond it. For products stored refrigerated, the limit is one and a half times the period and no more than six months beyond it³. ICH is consolidating its stability guidelines, including Q1E, into a single revised Q1 guideline⁴, so confirm the current version before applying these limits.

Stability often outlasts the label. A 2006 analysis of the federal Shelf Life Extension Program, which tests stockpiled products held under controlled conditions, found that 88% of 3,005 lots across 122 products were extended by at least a year, with an average extension of 66 months⁵. More recent testing points the same way, within limits. A 2025 study of expired hospital products found that several, including naloxone and dexamethasone, still retained their labeled content within acceptable limits, while every epinephrine sample fell well short⁶.

Those results come from stockpiles and small hospital samples rather than commercial labeling, yet they show why an extension is worth planning for, and why only stability data can justify one.

Until new stability data supports an extension and it is reflected in the labeled expiry, treat it as a scenario. Run the plan with the extended shelf life to see which lots return to supply, which shortages disappear, and which planned orders could move later. Keep the live plan on the approved expiry, so purchasing and production decisions never depend on an extension that has not happened yet.

06What to expect from your planning system

Once a portfolio spans many lots, sites, and channels, shelf life is too detailed to manage reliably by hand. In every planning run, a planning system should be able to:

• Check the remaining shelf life of every lot in every period, against the requirement where the lot will be used.
• Consume lots first expiry, first out, and take them out of the plan before they fall short.
• Exclude lots in quarantine or on quality hold until they are released.
• Carry retest dates as well as expiry dates at every level of the bill of materials.
• Flag lots approaching expiry early enough to act on them.
• Test a shelf-life extension as a scenario without changing the live plan.

SCmple applies these checks in every planning run, highlights lots expiring within 90 days after each run, and lets your team test a shelf-life extension as a scenario before it is approved.

References

1. U.S. Code of Federal Regulations, 21 CFR 211.166, Stability testing. Electronic Code of Federal Regulations. ecfr.gov
2. International Council for Harmonisation. ICH Q7, Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, section 11.6, Expiry and Retest Dating. November 2000. ema.europa.eu
3. U.S. Food and Drug Administration. Q1E Evaluation of Stability Data, Guidance for Industry. June 2004. fda.gov
4. International Council for Harmonisation. ICH Q1, Stability Testing of Drug Substances and Drug Products, draft guideline (Step 2b), which will supersede Q1A to Q1F. European Medicines Agency, April 2025. ema.europa.eu
5. Lyon RC, Taylor JS, Porter DA, Prasanna HR, Hussain AS. Stability profiles of drug products extended beyond labeled expiration dates. Journal of Pharmaceutical Sciences, 2006. doi.org/10.1002/jps.20636
6. Aljohar H, Altoum GH, Alkarni SA, Alburaidi MM, Alhabardi S. Quality assessment of some specific drug products beyond expiration dates in Saudi Arabia. Saudi Pharmaceutical Journal, 2025;33(3):9. doi.org/10.1007/s44446-025-00016-4