Does a phase-change pack hold a liraglutide shipment for forty-two days in transit?

Details up front: liraglutide · forty-two days.

I would rather understand the derivation than memorise the outcome.

Two people I asked gave two answers that differ by a factor of ten, which is suggestive.

What is the general form of this calculation?

42 days is 1008 hours, and phase-change shippers are qualified in hours: 96 and 120 are the common ratings. So 1008 hours is 10.5 times a 96-hour qualification and 8.4 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 888 to 912 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 1008 hours of data instead of an argument.

The relevant physics is latent heat: a phase-change pack holds temperature only while it is changing phase, and once it has melted it is a warm mass.

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.

Degradation pathway by condition

On the detail: 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.

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.

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

edited 22 May 2026 by Dr_Yusuf_Adeyemi — added the placebo-arm figures