David, my son uses the Medtronic Paradigm 712 pump. He changes the tubing (site) every 4 days. The hydrocortisone we use, Efcortisol comes in an ampoule and used here in the UK for the emergency injection kits and is very stable. Professor Hindmarsh of course had this tested in the labs too. The pump is programmed to automatically change the doses at specific times which are all programmed into the pump, so you never have to change the doses unless you want to switch to double or triple dose which is very easy to do, as again these rates are programmed in. There is even a remote control for the pump. The doses we use are worked out to suit the way my son metabolises the hydrocortisone and to mimic the circadian rhythm, there was a lot of blood testing done to tailor this, and then Professor Hindmarsh used his formula to work out the doses and times. The pump slowly infuses the hydrocortisone so you do not get the peaks and troughs as you do with the tablets, except where you want them, and at the dose you need.
KathyG