Chris and Carol, I found the information specific to hydrocortisone (cortef, etc.) at: www.emedline.com/lexicomp/datasets/anes_f/html/chapter/mono/fc063400.htm There is a good chart showing the biologic half-lives for all of the glucocorticoids at:: www.uspharmacist.com/NewLook/CE/glucocort/lesson.htm The initial dose of hydrocortisone will have an impact on the amount remaining after one half-life. I remember reading, at site that discussed the use of high steroid doses, that it takes about 3 days for 250 mg of hydrocortisone to clear from the body. The dose of hydrocortisone that your children were taking may not have been enough to last them the necessary 12 hours. I also found the following at: www.aafp.org/afp/990301ap/1190.html "Hydrocortisone is preferred over other glucocorticoids because it is short acting and can be given in pulses that mimic natural cortisol secretion. Equivalent dosages of prednisone or dexamethasone can be used to simplify dosing regimens in noncompliant patients; however, hydrocortisone is more physiologically similar to cortisol and has a lower potential for growth suppression in children." You might be interested to learn that I was one of the first CAH patients at NY Hospital's Department of Pediatric Endocrinology. I had been going there long before Dr. New arrived on the scene. Of course I taught her everything she knows. I'm quite proud of how she turned out. Joan