Serum ionic fluoride concentrations are significantly decreased after treatment with alendronate in patients with osteoporosis.

Background: We determined serum ionic fluoride (SIF) concentrations before and after treatment of osteoporosis with alendronate to clarify whether SIF concentrations directly reflect a change in bone metabolism.
Methods: A total of 45 postmenopausal women with primary osteoporosis who were treated with alendronate over a 6-month period were enrolled (mean age, 64.2 years). SIF concentrations were measured by the flow injection method with an ion-selective electrode. Concentrations of bone turnover markers (serum bone alkaline phosphatase, serum osteocalcin, serum type I collagen cross-linked N-telopeptide and urinary deoxypryridinoline) and lumbar spine BMD (LsBMD) were also measured. SIF, bone turnover markers and LsBMD before and after treatment were compared.
Results: Concentrations of SIF as well as concentrations of all bone turnover markers were significantly decreased after treatment: means (standard deviations) before and after treatment were 0.62 (0.13) and 0.32 (0.09) μmol/l, respectively (P<0.001) and the percent change was -46.3%. LsBMD was also significantly increased by 6.7% after treatment.
Conclusions: The reduction of SIF concentrations is probably caused by inhibition of bone resorption due to the action of alendronate. The findings suggest that SIF concentrations directly reflect a change in bone metabolism.
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