Effects of intravenous and oral dexamethasone on selected lymphocyte subpopulations in normal subjects.

Our studies describe the effects of 1 mg oral (PO) and intravenous (IV) administration of dexamethasone (DEX) on certain subpopulations of circulating lymphocytes in normal subjects. We compared the outcomes of PO and IV DEX administration because of individual differences in gastro-intestinal absorption of DEX and the issue of noncompliance in patients undergoing the dexamethasone suppression test (DST). Both routes of DEX administration were equally effective in suppressing plasma cortisol levels below 5 micrograms/dl, the customary criterion level. Both routes of DEX administration also significantly decreased the percent and absolute number of CD4+ cells, the CD4+/CD8+ ratio, and the percent and absolute number of virgin, but not of memory, CD4+ cells.