Breast cancer pills. Box and blister packs of Orimeten pills used in the treatment of breast cancer. Each pill contains 250 milligrams of the drug aminoglutethimide. This drug inactivates the enzyme aromatase, which is involved in the production of oestrogens (female sex hormones). Breast cancers are stimulated to grow by the presence of oestrogens in the blood, and a lack of them inhibits the growth of the tumour. Orimeten has also been used to treat prostate cancer. It has numerous side-effects, including drowsiness, nausea and insomnia, and its use has now been largely superceded by drugs such as tamoxifen.