Aminoglutethimide reduces the production of D5-pregnenolone and blocks several other steps in steroid synthesis, including the C-11, C-18, and C-21 hydroxylations and the hydroxylations required for the aromatization of androgens to estrogens, mediated through the binding of aminoglutethimide to cytochrome P-450 complexes. Specifically, the drug binds to and inhibits aromatase which is essential for the generation of estrogens from androstenedione and testosterone. A decrease in adrenal secretion of cortisol is followed by an increased secretion of pituitary adrenocorticotropic hormone (ACTH), which will overcome the blockade of adrenocortical steroid synthesis by aminoglutethimide. The compensatory increase in ACTH secretion can be suppressed by the simultaneous administration of hydrocortisone. Since aminoglutethimide increases the rate of metabolism of dexamethasone but not that of hydrocortisone, the latter is preferred as the adrenal glucocorticoid replacement. Although aminoglutethimide inhibits the synthesis of thyroxine by the thyroid gland, the compensatory increase in thyroid-stimulating hormone (TSH) is frequently of sufficient magnitude to overcome the inhibition of thyroid synthesis due to aminoglutethimide. In spite of an increase in TSH, aminoglutethimide has not been associated with increased prolactin secretion.
Aminoglutethimide inhibits the enzymatic conversion of cholesterol to D5-pregnenolone, resulting in a decrease in the production of adrenal glucocorticoids, mineralocorticoids, estrogens, and androgens.
Hepatic. 34-54% of the administered dose is excreted in the urine as unchanged drug during the first 48 hours, and an additional fraction as an N-acetyl derivative.
Oral LD50s (mg/kg): rats, 1800; dogs, >100. Intravenous LD50s (mg/kg): rats, 156; dogs, >100. Symptoms of overdose include respiratory depression, hypoventilation, hypotension, hypovolemic shock due to dehydration, somnolence, lethargy, coma, ataxia, dizziness, fatigue, nausea, and vomiting.