Droloxifene, a new antiestrogen. Hormonal influences in postmenopausal breast cancer patients.

Hormonal influences and pharmacokinetic aspects of the new antiestrogen droloxifene (3-hydroxytamoxifen) have been studied in a total of 148 postmenopausal patients with breast cancer. A negligible decrease in the gonadotropins LH and FSH was observed in patients treated with 20 mg (34 patients) and 40 mg (43 patients) of droloxifene (once daily). Serum concentrations of the gonadotropins obviously decreased (71 patients) with the highest dose of droloxifene (100 mg, once daily) given in this study. Sex hormone binding globulin rose only marginally in the 20- and 40-mg dose group. However, with 100 mg of droloxifene, a moderate increase was found, indicating some estrogenicity at higher doses. Rapid pharmacokinetic characteristics have been confirmed. The time to peak concentration ranges from 2 to 4 h, and the terminal half life is about 24 h, allowing interesting new schedules in endocrine therapy.