Does a phase-change pack hold a dulaglutide shipment for fourteen days in transit?

Details up front: dulaglutide · fourteen days.

I have worked this out and I would like someone to find the error, because I suspect there is one.

My working so far, for the record, is below, and I am fairly sure the error is in the unit conversion rather than the algebra.

How many significant figures are actually justified here?

14 days is 336 hours, and phase-change shippers are qualified in hours: 96 and 120 are the common ratings. So 336 hours is 3.5 times a 96-hour qualification and 2.8 times a 120-hour one. Past its rated duration a phase-change pack is not partial protection — it is thermal mass that has finished changing phase, after which the payload tracks ambient. On that reading the last 216 to 240 hours are room-temperature storage in a box. The qualification also assumes a stated ambient profile, and a lane that sits on an apron in August is not the profile the figure was measured against. If you want what happened rather than what was rated, a single-use electronic logger costs less than the assay you would otherwise run afterwards and answers it with 336 hours of data instead of an argument.

Start with the physical state, because it changes the answer completely and is the first thing to establish.

Asking a supplier to hold a shipment during a heatwave is reasonable and the better ones agree; the cost is a week and the benefit is a shorter warm exposure for anything in solution.

Reported and extrapolated stability by condition

Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.

Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.

Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.

Reconstituted material has a genuine cold-chain requirement and it starts the moment water is added.

Buy a logger if you actually want to know. Everything else is inference.

Answering this needs the transit duration and the ambient temperature, and then the arithmetic is straightforward.

A single phase-change pack in a thin-walled box holds below ten degrees for roughly one to two days at twenty-five degrees ambient, and under a day at thirty-five. On a nine-to-fourteen-day lane the material is at ambient for most of the journey whatever was packed with it.

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.

Solid-state stability of lyophilised peptides at ambient temperature is documented in formulation studies with residual moisture as the dominant variable.

The caveat is that a warm transit is survivable for a solid and materially different for a solution.

The domestic leg is the part you control. Refrigerate it promptly.

The short version: a spent cold pack on arrival is expected, the solid does not mind, and the pack was never going to last twelve days.

That is the argument for shipping lyophilised rather than for shipping colder. A dry powder with low residual moisture is stable at ambient for months; the pathways that matter need water.

A single-use temperature logger costs a few pounds, records the whole journey and converts an argument into a record. If the history matters, this is the answer.

Nothing here is medical advice, and research-use compounds are not approved for human use.

A liquefied pack is expected. It is not evidence of a problem.

The honest answer is that the cold pack is doing much less than people think and that shipping lyophilised is what actually protects the material.

Once the parcel arrives, the domestic leg is the controllable part: get it into the refrigerator promptly rather than leaving it in a warm hallway for a day.

Single-use temperature loggers are standard practice in supply chains where temperature genuinely matters and are inexpensive at parcel scale.

A cold pack tells you nothing about the eleven days before the last one.

Lyophilised tolerates the lane. That is the answer for almost every order.

edited 6 Apr 2025 by deamidation_watch — added the placebo-arm figures

On the detail: the domestic leg after arrival is the part most often left in a warm hallway and least often worried about.

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.

Phase-change pack hold time is a function of mass, latent heat and insulation, and published figures for small parcels are on the order of one to two days.

The caveat is that "within specification" and "unchanged" are different claims. A vial can lose a few per cent of content and still be usable for its purpose while no longer matching its certificate.

Solutions are a different question and deserve the worry the solids get.

edited 22 Apr 2025 by esben_lykke — updated for the 2026 guidance change