Fluoride bioavailability from slow-release sodium fluoride given with calcium citrate.

Clinical pharmacology of slow-release sodium fluoride given with calcium citrate was examined in acute and long-term studies. Following a single oral administration of 50 mg slow-release sodium fluoride, a peak serum fluoride concentration (Cmax) of 184 ng/ml was reached in 2 h; thereafter, serum fluoride concentration declined with a T1/2 of 5.9 h. The concurrent administration of calcium citrate (400 mg calcium) gave an equivalent Tmax (time required to attain Cmax) and T1/2, but a lower Cmax of 135 ng/ml. The coadministration of a meal with fluoride also reduced Cmax but increased Tmax. The area under the serum concentration curve of slow-release sodium fluoride was reduced 17-27% by a meal or calcium citrate. Thus, calcium citrate reduced fluoride absorption and peak fluoride concentration in serum of slow-release sodium fluoride but did not affect the time required to reach peak concentration or the rate of subsequent decline. The effect of a meal was similar, except for a longer period required to reach peak serum concentration. During long-term administration of 25 mg slow-release sodium fluoride coadministered with 400 mg calcium as calcium citrate on a twice daily schedule, the trough level of serum fluoride could be kept between 95 and 190 ng/ml, believed to be the therapeutic window.

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 less than .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.

Safe and effective treatment of osteoporosis with intermittent slow release sodium fluoride: augmentation of vertebral bone mass and inhibition of fractures.

The value of intermittent slow release sodium fluoride treatment in the management of osteoporosis was studied by a comprehensive metabolic and clinical assessment during a long term trial. Its effect was compared with that of a large dose of 1,25-dihydroxyvitamin D [1,25-(OH)2D] given for a short period preceding each fluoride treatment period in another group of randomly selected patients. The 24 patients in group I (3 idiopathic and 21 postmenopausal) received cyclic treatment in repeated 5-month cycles; each cycle was initiated by 1,25-(OH)2D (2 micrograms/day) for 2 weeks, followed for 3 months by sodium fluoride (slow release, 25 mg twice daily) with 25-hydroxyvitamin D (50 micrograms twice weekly) and calcium supplements (to bring total calcium intake to 1500 mg/day), and was concluded by 6 weeks of 25-hydroxyvitamin D and calcium supplementation without sodium fluoride. The 21 patients in group II (3 idiopathic and 18 postmenopausal) received the same treatment, except for the omission of 1,25-(OH)2D. In both groups, the serum fluoride level was maintained within 5-10 mumol/L (95-190 ng/mL) during fluoride treatment, and serum osteocalcin concentrations correlated positively with the duration of treatment. However, vertebral bone mineral content (L2-L4) did not increase significantly in group I, whereas it rose significantly in group II (fractional change, +0.031/2.4 yr in group I vs. + 0.118/2.9 yr in group II; P less than 0.005). Although bone histomorphometric analyses disclosed overall improvement in both groups, only group II had significant increases in the mineral apposition rate [0.5 +/- 0.2 (+/- SE) to 1.4 +/- 0.2 micron/day; P less than 0.05] and the adjusted apposition rate (0.2 +/- 0.1 to 0.7 +/- 0.1 micron/day; P = 0.04). The vertebral fracture rate significantly declined in both groups, but more so in group II. Excluding the first year of treatment, the fracture rate during treatment in group II of 0.03/patient yr was significantly lower than that of 0.28/patient yr in group I (P less than 0.05). The treatment was well tolerated in both groups; only 16% of patients had either gastrointestinal or rheumatic complications. We conclude that intermittent sodium fluoride treatment without 1,25-(OH)2D provides safe and effective treatment of osteoporosis, marked by formation of new adequately mineralized bone, a rise in vertebral bone mass, and reduced frequency of vertebral fractures. The addition of 1,25-(OH)2D treatment before initiation of each fluoride phase yielded a less favorable response.