Pharma Retention Sample Quantity Calculator
Retention samples are kept so that the batch can be examined later if there is a complaint or a suspected defect. Their number and the time you keep them drive storage space. This calculator estimates both from your test volume, batch rate and shelf life.
Your numbers
All tests in the finished product specification, including a sterility test where applicable, once.
EU Annex 19 says at least twice the quantity needed for the full analytical control. Check your local rule.
EU Annex 19 asks for at least one year after expiry for finished product samples.
Your results
Planning estimate. Confirm quantity and period against the regulation that applies to your market, such as EU GMP Annex 19, and your own procedure. Samples destroyed after the retention period reduce the steady state count once the first cycle is complete.
Samples in store vs shelf life
Sweeps Shelf life from 6 to 60, holding your other inputs fixed.
Track retention samples by batch
Want retention locations and destruction dates linked to batches in your ERP? Ask for an expert review.
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How to use the calculator
Enter the number of units needed for one full analysis, the multiplier your rule requires, batches per year, shelf life, and extra years after expiry. Read the units per batch, years held, and steady state samples in store. Divide by units per box to plan shelves in the controlled storage room. The chart shows how storage grows with shelf life so you can see the cost of a longer expiry date.
- Use units of the finished pack, not bulk
- Add separate runs for each strength and pack size
- Retain starting materials too where your rules require it
The rule and the maths
EU GMP Annex 19 on reference and retention samples says that a retention sample of finished product should be at least twice the quantity needed to carry out all tests in the marketing authorisation, with exceptions, and kept for at least one year after expiry of the batch. In the US, 21 CFR 211.170 requires reserve samples at least twice the quantity needed for all authorised tests except sterility and pyrogen, kept for one year after expiry. The formula here is units per batch times batches per year times years held.
Reading the result and mistakes
With the defaults, each batch keeps 120 units for four years, and 24 batches per year gives about 11,520 units in store at steady state. Mistakes include forgetting that storage conditions must match the label, leaving damaged boxes in place, and ignoring the stock of retained samples of active ingredients. Also make sure the retention room is covered by temperature monitoring and access control, and that sample destruction is documented.
- Store in the same pack type as marketed
- Record destruction dates once the period ends
- Review sample inventory with a periodic physical check
Frequently Asked Questions
Is the multiplier always two?
Two times the full analytical quantity is the common rule in the EU and US, but exceptions exist, such as for sterility testing and for very small batches. Check the rule that applies to each product and market.
How long must retention samples be kept?
For finished product, EU Annex 19 says at least one year after expiry. In the US it is one year after expiry for drugs with an expiry date, with longer periods for some products. Always apply the longer of your applicable rules.
Do I keep samples of every batch?
Generally yes, one set per batch of finished product, and for each packaging site. Some products and contract arrangements have specific rules, so confirm in your quality agreement and procedures.
Can I destroy samples after testing?
Retention samples are not for routine testing. If used for an investigation, record the quantity taken and make sure enough remains. Destroy them only after the full retention period under a documented procedure.
If retention samples are tracked on paper and you would like batch, location and destruction dates managed in the ERP or QMS, Netray can help set that up.
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