Most modern steroid enemas are foam based - as the likelihood of someone with colitis being able to retain a water based enema is quite low. These act topically applying the steroid directly to the colon - with only small amounts being absorbed into the bloodstream. This makes side effects less likely. The downside is that they can only reach the descending colon and rectum - so for those with extensive colitis oral steroids may be needed. A combination of Entocort and steroid enemas can provide topical treatment to the majority of the colon - again minimizing side effects. As the two main steroid enemas differ quite greatly I will cover them separately.
Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandrosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.