The answer should really be Hospira water should be stored between 20-25c and not refrigerated. This is not a universal recommendation for ALL BAC water. I got an extreme amount of heat for saying this on STG where they are Hospira fanatics and won’t entertain any discussion of any other BAC water.
The reason Pfizer have set a 20-25c temp range is because they have received reports that their formulation (only Hospira, not all BAC water) suffers from a reversible precipitation of the benzyl alcohol at low temperatures. This is completely reversed when the water comes to room temperature and does not affect the efficacy of the benzyl alcohol. But to avoid any risk of people injecting precipitate if not leaving it come to room temp, and the fact that stability for 28 days is supported by data at room temperature, it is much easier to put a notice saying keep at room temp for 28 days to avoid any risk of injecting precipitate. If you are going over 28 days, which nearly everyone does then refrigeration starts to make more sense as it will further reduce microbial growth as the risk of that growth starts to rise. Whether it actually makes any practical difference to actual infections I am not sure. It probably depends how meticulous you are when you recon, how many times you spike the vial, and a bit of luck, all mixed with how long you extend the 28 day period. For most MDVs you’d be expecting to stab it 20-30 times but for peptides it’s probably closer to 10 and that reduces the risk quite a bit. Personally I’ve kept BAC in the fridge with no signs of precipitation at any time, but I always allow it to come to room temperature before I reconstitute and thoroughly inspect it beforehand.
