What is buffer stock in clinical trials?
Buffer stock (or safety stock) in clinical trials is investigational product held above the forecasted demand to absorb uncertainty — faster-than-expected enrollment, shipment delays, temperature excursions, or damaged kits. It is typically expressed as a percentage of forecast demand or as months of forward coverage at a depot or site.
Buffer stock exists because a clinical supply chain cannot run lean the way a commercial one can. A stockout at a site is not a lost sale — it can mean a missed dose for an enrolled patient, a protocol deviation, or a site that stops screening. Sponsors therefore deliberately hold more inventory than the forecast strictly requires.
The trade-off is waste. Investigational product is expensive, often has limited shelf life, and overage that expires at a depot is written off. Setting buffer levels is a judgment call that weighs enrollment uncertainty, lead times for resupply, shelf life, and the clinical consequence of a stockout — and the right answer usually differs by depot, by study phase, and over the life of the trial.
In practice, buffer policy should be revisited as part of the monthly planning cycle: early in a study, when enrollment is most uncertain, buffers are typically generous; as enrollment completes and the remaining demand becomes predictable, carrying the same buffer just creates expiry risk.
How TrialSupply handles this
TrialSupply's supply planning applies buffer stock policies on top of the demand forecast when calculating supply requirements, so planners can see forecast demand, buffer, and resulting inventory position by month in one planning book — and adjust buffer assumptions as trial uncertainty changes.