Transfer of Metyrapone and Its Metabolite, rac-Metyrapol, Into Breast Milk

Abstract

Metyrapone, an inhibitor of corticosteroid biosynthesis, is used in the diagnosis and treatment of adrenocortical hyperfunction. The authors describe the excretion of metyrapone and its metabolite, rac-metyrapol, in milk from a lactating woman requiring metyrapone treatment (250 mg 4 times daily). At steady state, the average concentrations in milk and absolute and relative infant doses were 11 µg/L, 1.7 µg/kg/d, and 0.02%, respectively, for metyrapone, and 48.5 µg/L, 7.3 µg/kg/d, and 0.08%, respectively, for rac- metyrapol . The findings suggest that maternal metyrapone use during breastfeeding is extremely unlikely to be a significant risk for the breastfed infant. J Hum Lact. 25(4):451-454.