Effect of low-dose transdermal E2/NETA on the reduction of postmenopausal bone loss in women

OBJECTIVE: To assess the efficacy of a continuous-combined transdermal patch (estradiol/ norethisterone acetate [E(2)/NETA] 25/125; Estragest TTS, Novartis, Basel, Switzerland) in the reduction of bone loss in postmenopausal women. DESIGN: In a 96-week, double-blind, randomized, multicenter, parallel study, 124 healthy women with an intact uterus more than 4 years after menopause received either transdermal continuous-combined E(2)/NETA (0.025/0.125 mg/day) or placebo patch for 24 treatment cycles; diet was normalized for calcium intake. Lumbar spine bone mineral density (BMD) ranged from 0.969 to 0.805 g/cm2 with a mean annual BMD decrement ranging from 3% to 8% within the last 24 months. BMD at lumbar spine L(2)-L(4) (postero-anterior) and femur were assessed by dual energy x-ray absorptiometry after 6, 12, and 24 cycles. Efficacy variables included measurement of biochemical markers of bone turnover (3, 6, 12, and 24 months). RESULTS: BMD at lumbar spine was significantly higher at all time points in the E(2)/NETA group than in the placebo group (P < 0.0001). Significant increases in BMD (P < 0.0008) from baseline were observed at all sites after 24 months in the E(2)/NETA group compared with placebo, which demonstrated a decrease from baseline. At endpoint, statistically significant decrements in the values of bone remodeling markers were observed (P < 0.05) with E(2)/NETA. CONCLUSIONS: E(2)/NETA 25/125 Estragest TTS was more effective than placebo in reducing the activation frequency of bone remodeling and in preventing bone loss at the spine and hip. Effects on the hip were similar to those observed for higher doses of estrogen.