A drug that inhibits the production of CORTISOL in the adrenal cortex, resulting in an increase in ACTH (ADRENOCORTICOTROPHIC HORMONE) production and thus (completing the feedback control cycle) greater synthesis of the chemical precursors of cortisol. Metyrapone is used in diagnosis and treatment of patients with CUSHING'S SYNDROME (a condition caused by excess amounts of corticosteroid hormones in the body) where surgery is not possible. It also has a use in resistant oedema due to increased aldosterone secretion in cirrhosis, nephrotic syndrome, and congestive heart failure.