Tibolone Stops Bone Loss, Reduces Hot Flashes.

WASHINGTON -- The synthetic steroid tibolone is proving to prevent bone loss and to combat hot flashes and vaginal dryness as effectively as hormone replacement therapy in clinical trials, researchers reported at an international symposium on women's health and menopause.

Tibolone is not yet commercially available in the United States but has been used to treat menopausal symptoms in Europe and Asia for the past 20 years. The drug is currently under review by the Food and Drug Administration and will be sold under the trade name Xyvion if it is approved for use in the United States, according to the manufacturer, Organon Inc., West Orange, NJ.

Tibolone has been studied extensively in the United States in recent years, and the results of a dose-finding clinical trial involving 40 American medical centers show that even relatively low doses clearly prevent bone loss in the early postmenopausal period, said Dr. J. Christopher Gallagher, professor of internal medicine and endocrinology at Creighton University, Omaha, Neb.

The trial involved 770 healthy women with an average age of 52 years who had no clinical or radiologic evidence of osteoporosis and who had experienced menopause a mean of 2.5 years earlier. The women were randomly assigned to receive a placebo (150 subjects) or daily treatment with 0.3 mg (153 subjects), 0.625 mg (158 subjects), 1.25 mg (154 subjects), or 2.5 mg of tibolone (155 subjects). The standard dose given to women in Europe is 2.5 mg.

Bone mineral density (BMD) at the lumbar spine, as measured by dual-energy x-ray absorptiometry, clearly increased with the three higher dose levels of tibolone and showed no change at the lowest dose level. In contrast, spinal BMD significantly decreased in women taking placebo.

The mean bone loss was -2.5% with placebo, and the mean bone gain was 2.4% with the highest dose of the drug, "so the net difference between high-dose tibolone and placebo was approximately 5%," said Dr. Gallagher, who has received research funding from Organon.

Bone mineral density at the hip showed a similar pattern, increasing by 2.2% with the highest dose of tibolone and decreasing by 2% with placebo, for a net difference of more than 4%. BMD measurements at the femoral trochanter followed the same pattern.