Determination of aminoglutethimide and N-acetylaminoglutethimide in human plasma by reversed-phase liquid chromatography.

A liquid chromatography method for the determination of aminoglutethimide and N-acetylaminoglutethimide in human plasma is described. The assay involved precipitation of the plasma proteins using a mixture of acetonitrile and perchloric acid, without an extraction procedure. The supernatant was subjected to chromatography on a 3-micrometers ODS Hypersil column eluted isocratically with 11% acetonitrile in 100 mM ammonium formate buffer, pH 3.5. The absorbance was routinely recorded at 242 nm. The standard curves were linear in the range of 0.1-100 micrograms/ml, and the lower detection limit was approximately 0.1 microgram/ml for aminoglutethimide and its plasma metabolite N-acetylaminoglutethimide. The precision of the method, given as the coefficient of variation, was 3.9%. With this method, it was determined that aminoglutethimide and N-acetylaminoglutethimide were present in the plasma of patients receiving single-dose or continuous treatment with aminoglutethimide for breast cancer. No N-formylaminoglutethimide or nitroglutethimide could be demonstrated in the plasma from these patients. Interference from several drugs commonly given to patients with breast cancer was ruled out.