Effect of aminoglutethimide on antipyrine, theophylline, and digitoxin disposition in breast cancer.

The influence of aminoglutethimide (AG) on antipyrine, theophylline, and digitoxin kinetics was examined. Antipyrine was given as a single test dose before and after 3 mo of AG treatment, whereas theophylline and digitoxin kinetics were investigated at steady state in patients receiving these drugs therapeutically before and after AG therapy. During AG treatment, mean clearance rates for antipyrine, theophylline, and digitoxin increased by 81%, 32%, and 109%. Together with earlier reports of effects of AG on warfarin and dexamethasone disposition and on its own metabolism, these findings indicate that AG is a potent inducer of drug metabolizing microsomal monooxygenases of the liver. Since many drugs known to be metabolized by this enzyme system are frequently used for concomitant conditions in patients with breast cancer, interactions with AG are to be expected.