Efficacy and safety of oral tibolone 1.25 or 2.5 mg/day vs. placebo in postmenopausal women.

Background: tibolone at usual doses of 2.5 mg/day in postmenopausal women has been shown to improve climacteric complaints, without affecting endometrial thickness and lipid profile or blood glucose. However, the potentially similar efficacy, but better tolerability, of a low dose of this drug (1.25 mg) has never been established.

Methods: 162 healthy, non-obese, post-menopausal women, aged 40-65 years, with an intact uterus were enrolled in a national, single centre, randomised, double blind, placebo controlled, parallel group trial. After 1 week of runin, patients were treated for 24 weeks with placebo, tibolone 1.25 mg or 2.5 mg/day. During the study laboratory tests, endometrial ultrasound scans and mammography were performed. Occurrence of menopausal signs and symptoms, including vaginal bleeding, and quality of sexual life were also checked.

Results: in the 120 patients terminating the study without major protocol violations, climacteric symptoms were similarly improved by tibolone 1.25 and 2.5 mg (78% and 90% reduction at week 24 for hot flushes, 36% and 34% for sweating episodes and 44% and 51% for vaginal dryness), but not by placebo. Benefits occurred earlier in the group treated with tibolone 2.5 mg. Quality of sexual life was almost invariably improved by tibolone as compared to placebo, but improvement occurred earlier in the tibolone 1.25 mg group. Severity of vaginal bleeding was not different between placebo and active treatment groups, except at week 12 when was higher. At the end of treatment vaginal bleeding occurred in 15% of patients treated with placebo, 14% treated with tibolone 1.25 mg and 12% treated with tibolone 2.5 mg. Endometrial thickness and breast density were not changed by treatment, as well as FSH, 17-beta-estradiol, total cholesterol, HDL and LDL cholesterol, triglycerides and blood glucose. Adverse events were reported by 14.7%, 26.7% and 24.4% of patients treated with placebo, tibolone 1.25 mg and tibolone 2.5 mg/day, respectively.

Conclusions: tibolone at doses of 1.25 or 2.5 mg/day given for 24 weeks to postmenopausal women displayed similar efficacy and safety profiles, though were more effective than placebo. Tibolone 1.25 mg induced a more gradual relief from climacteric symptoms and a more prompt improvement of sexual function.