Why does RIA prefer prednisone to other forms of corticosteroid like dexamethasone?
Prednisone is the preferred corticosteroid for several reasons. First, it is highly bound to the blood protein albumin. This complex is large and has difficulty crossing the placenta. In addition, an enzyme in the placenta, beta-2-dehydrogenase, inactivates any free prednisone that does get across the placenta. The fetal liver is unable to reactivate the prednisone until about week 30 of gestation. At that time, the active steroid may help increase surfactant production, which helps to mature the fetal lungs.
