Trilostane, an orally active inhibitor of steroid biosynthesis.

Trilostane is a competitive inhibitor of 3beta-hydroxysteroid dehydrogenase. In vitro, the drug inhibits conversion of pregnenolone to progesterone but does not alter conversion of cholesterol to pregnenolone nor progesterone to corticoid hormones. When given orally to rats, trilostane inhibits corticosterone and aldosterone production and elevates circulating levels of pregnenolone at doses lower than those that produce adrenal hypertrophy or inhibit gonadal steroidogenesis.