Accepted answer
Five days at 2–8 °C is about 5 refrigerated days of equivalent exposure. 2–8 °C is the condition the rule of thumb is anchored to, so it is the baseline rather than a multiplier: everything else in this thread is quoted relative to it. At 5 equivalent days a test is more likely to reassure you than to tell you something, which is a legitimate reason to run it and a poor reason to expect a finding. Either way, record the five days and the temperature now, while you still know them; an excursion you did not write down is an excursion you cannot interpret later.
Start with the physical state, because it changes the answer completely and is the first thing to establish.
A pack that arrived hard tells you about the last day of transit only, since it will have melted and, if the ambient dropped, partially refrozen.
Reported and extrapolated stability by condition
| State | Condition | Usable window | Basis |
|---|
| Lyophilised solid | −20 °C, sealed, dry | 24–36 months | Supplier guidance |
| Lyophilised solid | 2–8 °C, sealed | 12–24 months | Supplier guidance |
| Lyophilised solid | 25 °C, sealed | 4–8 weeks | Extrapolated (Arrhenius) |
| Lyophilised solid | 40 °C, sealed | 1–2 weeks | Extrapolated |
| Solution, preserved | 2–8 °C | 28 days | USP microbiological convention |
| Solution, preserved | 25 °C | 3–7 days | Extrapolated |
| Solution, unpreserved | 2–8 °C | 24 hours | USP microbiological convention |
Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.
Arrhenius behaviour means the degradation rate roughly doubles per ten degrees. A week at thirty degrees is therefore a meaningful exposure for a solution and an immaterial one for a dry solid.
Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.
Nothing here is medical advice, and research-use compounds are not approved for human use.
The domestic leg is the part you control. Refrigerate it promptly.
4Worth adding that residual moisture predicts this better than any printed date. – Dr_Ilse_Vandenberg 23 days ago add a comment