It means "as necessary" The label would say something like "Take as needed for adrenal insufficiency".  It’s likely the same thing as on a vial of solu-cortef which are usually written as PRN.  "Take as needed" is tough thing to argue with.

While I have always known about this this loophole in prescribing meds, it was only after I got sick a few weeks back that I revisited it.   My pharmacist was laughing when I came in with several different scripts for different dosages of prednisone--each for 5-10 pills, all written to take as needed.  I told him I was opening up a prednisone stand at the end of my driveway.

Betsy