Attainment of therapeutic fluoride levels in serum without major side effects using a slow‐release preparation of sodium fluoride in postmenopausal osteoporosis

The bioavailability, biochemical effects, and safety of a slow‐release preparation of sodium fluoride were examined. In 8 normal volunteers, a single administration of slow‐release sodium fluoride (25 mg) caused a slow rise and gradual decline in serum fluoride concentration, thus avoiding sharp peaks produced by a rapid‐release preparation. In 37 patients with postmenopausal osteoporosis, serum fluoride concentration was kept within the “therapeutic window” (95‐100 ng/ml) during long‐term intermittent sodium fluoride (slow‐release) therapy (25 mg twice/day, given for 3 months in each 5‐month cycle over five cycles). Serum fluoride was also kept within the therapeutic window in 64 patients who took sodium fluoride (slow release) continuously over 12 months. Serum osteocalcin concentration increased progressively during fluoride treatment (correlation coefficient of 0.88, p < .001 for the relationship between serum osteocalcin and duration of therapy). Side effects to slow‐release sodium fluoride therapy, assessed in 101 patients at two study sites, were minor and included diarrhea in 2 patients, nausea in 2 patients, abdominal pain and cramping in 2 patients, foot pain in 2 patients, and joint pain in 6 patients. Thus, slow‐release sodium fluoride confers desired level of fluoride in serum, while providing safety of usage.