Metyrapone (trade name Metopirone) is a drug used in the diagnosis of adrenal insufficiency and occasionally in the treatment of Cushing's syndrome (hypercortisolism). Metopirone, metyrapone USP, is an inhibitor of endogenous adrenal corticosteroid synthesis, available as 250-mg capsules for oral administration. The pharmacological effect of Metopirone is to reduce cortisol and corticosterone production by inhibiting the 11-β-hydroxylation reaction in the adrenal cortex. Removal of the strong inhibitory feedback mechanism exerted by cortisol results in an increase in adrenocorticotropic hormone (ACTH) production by the pituitary. With continued blockade of the enzymatic steps leading to production of cortisol and corticosterone, there is a marked increase in adrenocortical secretion of their immediate precursors, 11-desoxycortisol and desoxycorticosterone, which are weak suppressors of ACTH release, and a corresponding elevation of these steroids in the plasma and of their metabolites in the urine. These metabolites are readily determined by measuring urinary 17-hydroxycorticosteroids (17-OHCS) or 17-ketogenic steroids (17-KGS). Because of these actions, Metopirone is used as a diagnostic test, with urinary 17-OHCS measured as an index of pituitary ACTH responsiveness. Metopirone may also suppress biosynthesis of aldosterone, resulting in a mild natriuresis.

(R)-Aminoglutethimide is R-isomer of racemate anti-steroid drug Aminoglutethimide, marketed by Novartis for the treatment of Cushing syndrome and other conditions. (R)-Aminoglutethimide was shown to more active than (S)-isomer in inhibiting corticosteroid release in rats, more potent in inhibiting aromatization of testosterone by human placental microsomes. (R)-Aminoglutethimide was investigated in a clinical trial against breast cancer, where it was found to enhance the clearance rate of plasma estrone sulfate.

(S)-Aminoglutethimide is S-isomer of racemate anti-steroid drug Aminoglutethimide, marketed by Novartis for the treatment of Cushing syndrome and other conditions. (S)-Aminoglutethimide was shown to less active than (R)-isomer in inhibiting corticosteroid release in rats, less potent in inhibiting aromatization of testosterone by human placental microsomes.