Mifepristone: treatment of Cushing's syndrome

Mifepristone is a potent antagonist of glucocorticoid and progesterone receptors. It is the only drug administered to humans with these actions. Exploration of mifepristone in the treatment of Cushing's syndrome is in its infancy. The cases reviewed in this report comprise the entire medical literature. Development and availability of mifepristone has been severely restricted because of controversy surrounding its ability to function as an "abortion pill." As the political controversy abates, increasing studies of this drug may be anticipated in patients with glucocorticoid excess. Although the authors have highlighted therapeutic trials with the drug, they also note that diagnostic uses in cases of glucocorticoid excess may be of interest. Some cases of endogenous Cushing's syndrome are difficult to diagnosis and a glucocorticoid antagonist may be as useful as a glucocorticoid agonist (such as dexamethasone) in the dynamic evaluation of glandular function. In particular, mifepristone might be useful in distinguishing pituitary from occult ectopic ACTH-secreting tumors. One of the primary problems surrounding the use of mifepristone in cases of Cushing's syndrome is the long half-life of the drug and the necessity to titrate doses carefully in a manner that avoids signs and symptoms of glucocorticoid deficiency. Biochemical markers reflecting the "glucocorticoid status" of a patient would be useful for dose adjustment and monitoring and would improve the risk to benefit ratio for mifepristone treatment of Cushing's syndrome.