Journal of Clinical Endocrinology & Metabolism, Vol 69, 932-938, Copyright © 1989 by Endocrine Society

ARTICLES

The response of vertebral bone mineral density during the treatment of osteoporosis with sodium fluoride

AB Hodsman and DJ Drost
Department of Medicine, St Joseph's Health Centre, London, Ontario, Canada.

Forty-eight female patients with postmenopausal osteoporotic vertebral compression fractures were treated with sodium fluoride and calcium supplements; their response to treatment was documented by sequential measurements of vertebral and forearm bone mineral density (BMD). During treatment 25 patients developed significant side-effects due to fluoride, and ultimately, 18 patients (37%) were intolerant of the drug after 17.3 +/- 7.3 (+/- SD) months. The remaining patients were followed for 29.4 +/- 9.6 months. By linear regression analysis, 69% of patients had a positive slope of vertebral BMD vs. time of greater than 0.0017 g/cm2.month (range, 0.0017-0.01) and were classified as treatment responders. The increment in vertebral BMD above the baseline value over time was described by the relationship delta BMD (g/cm2.month) = 0.042 + 0.0053 x months, equivalent to a rate of 8.4%/yr. Because the rates of increasing BMD were very variable, it was difficult to determine in individual patients the point at which a positive response to treatment had occurred; by calculating the 95% confidence target BMD by which the BMD must rise above the initial value before discounting the imprecision of the measurements (0.062 g/cm2), only 70% of responders were identified by 12 months. The total cumulative dose of sodium fluoride (31.3 +/- 16.4 g) was significantly higher in patients classified as responders than in the nonresponders (20.6 +/- 13.4 g; P less than 0.05), probably because of differences in side-effects between the two groups. In contrast, forearm BMD fell significantly in the responders by an average of 7.7%/yr, suggesting the possibility of a preferential improvement in axial bone density at the expense of cortical bone. Thus, the majority of patients treated with fluoride respond with increasing vertebral BMD, but it may take 12- 24 months to identify these individually.