Absolute bioavailability of fluoride from disodium monofluorophosphate and enteric-coated sodium fluoride tablets

Abstract

Objectives: The absolute bioavailability and other pharmacokinetic parameters of two fluoride formulations were investigated in 13 healthy volunteers, aged 61–70 years.

Methods:

The following formulations were administered, under fasting conditions, in a single-dose three-way cross-over design: tablets of 76 mg disodium monofluoro phosphate (MFP, equivalent to 10.0 mg F⁻ ion), enteric-coated (e.c.) tablets of 25 mg sodium fluoride (NaF_or, equivalent of 11.3 mg F⁻ ion), and an isoosmotic aqueous injection solution (4 ml) of 22.1 mg sodium fluoride (NaF_iv, equivalent of 10.0 mg F⁻ ion). There was a wash-out period of at least one week between each administration. Blood was sampled before and during a 24-hour period after administration. For F⁻ excretion urine was sampled 48 hours before (baseline) and over the 48 hours after the adminstration.

Results:

The mean t_1/2 values of the three formulations were 8.3, 8.7 and 8.3 h for MFP, NaF_or and NaF_iv respectively, and were not significant different. Mean C_max after MFP was significantly higher than after NaF_or [344 vs 142 μg⋅l⁻¹]. Mean t_max for MFP was shorter than for NaF_or [1.1 vs 4.6 h]. MFP had significantly higher bioavailability [102.8%] than NaF_or [64.2%].

Conclusion:

The MFP formulation showed higher bioavailability with smaller variation than the NaF_or formulation. MFP is preferable, therefore, for fluoride therapy in clinical practice, and changing from NaF_or to MFP will require adjustment of the dose.