SODIUM FLUORIDE FOR OSTEOPOROSIS NEEDS ADDITIONAL STUDIES, FDA's

SODIUM FLUORIDE FOR OSTEOPOROSIS NEEDS ADDITIONAL STUDIES, FDA's Endocrinologic and Metabolic Drugs Advisory Committee recommended at its Oct. 12 meeting. The committee unanimously agreed that data presented from NIH-sponsored trials at the Mayo Clinic and the Henry Ford Hospital in Detroit "did not provide adequate evidence of safety and efficacy for long-term immediate-release sodium fluoride therapy in the treatment of postmenopausal osteoporosis." Although the clinical studies did not show a reduction in osteoporatic fractures, several committee members pointed out that the data indicated that fluoride may have a potential role in osteoporosis. For example, committee member Stephen Winters, MD, Pittsburgh's Montefiore Hospital, commented: "The data showing that fluoride increases bone density [is] very convincing and probably biologically important." The committee presented its request for additional data as a compromise between the potential usefulness of fluoride and the dearth of other osteoporosis therapies. Summarizing the committee consensus, Chairman Saul Genuth, MD, said, "if there was something else . . . on the horizon that was going to be very useful in the prevention or the reversal of osteoporosis, I would probably recommend that the FDA quietly forget about fluoride." However, Genuth continued, "I suspect that buried in the fluoride story there is some efficacy," and "because we don't have a better contender . . . I think the FDA should consider encouraging other studies." Genuth is director of the Radioimmunoassay Laboratory at the Mt. Sinai Hospital of Cleveland. Noting "the magnitude of the clinical problems in our aging population," committee member Susan Ratzan, MD, University of Connecticut, called for "more studies, both of the basic kind and larger, well-controlled multicenter trials." Other committee suggestions for future fluoride research included earlier intervention and/or prophylactic use in menopausal women, different formulations such as monoflorophosphate (MFP), and combination therapies with growth factors or steroids. The two studies presented at the meeting began in 1981 and were conducted under NIH grants. Both were randomized, double-blind, placebo-controlled studies examining the effectiveness of 70 mg immediate-release sodium fluoride daily in preventing vertebral fractures associated with osteoporosis in women aged 45 to 75. A noncommercial fluoride preparation supplied by NIH was used in each trial. According to the FDA overview, presented by the Metabolism and Endocrine Drug Products Division's Sam Dutta, the rationale for the protocol was based on previous studies showing that fluoride could increase bone density by promoting osteoblast activity. However, Dutta noted, some researchers felt that the bone formed by fluoride therapy displayed "defective mechanical properties" that might increase the rate of other fractures even if it reduced the risk of vertebral fracture. The 86-patient study at Henry Ford "was not able to show that the level of fracture occurrence was significantly different in the placebo and sodium fluoride groups . . . as assessed by measures of vertebral height, radiography and bone scan," concluded the Ford Hospital's Michael Kleerekoper, MD, who presented the results. The larger 135-patient Mayo Clinic trial detected a 15% decrease in the vertebral fracture rate in the fluoride group compared to placebo. However, Mayo researcher L. Joseph Melton, MD, stated that this result was "not statistically significant." In a development that Melton called "at the least, worrisome," the fluoride patients experienced an increased rate of non-vertebral fractures that was "two-fold, though not statistically significant." In conclusion, Melton stated, fluoride did show an ability to increase bone mass, but "overall fragility was increased and overall bone quality decreased . . . These two phenomena account for the failure of vertebral fractures to decrease, and for the increase in non-vertebral fractures."