Effect of age on the disposition of sodium fluoride.

Sodium fluoride (NaF) is used in the treatment of axial osteoporosis and so is mostly given to old patients. Since its pharmacokinetics has not been studied in the elderly, the pharmacokinetics of an enteric-coated tablet containing 50 mg NaF has been investigated in 15 aged inpatients (aged 65 to 75 y) and 12 young healthy volunteers (aged 21 to 26 y). The serum AUC of fluoride was 1.7-time higher in older than in younger subjects. There was a strong inverse correlation between the AUC and either body surface area (BSA) or glomerular filtration rate (GFR), both of which were very much lower in the elderly. This concluded that if efficacy or safety are related to the bioavailability of fluoride, it may be valuable to adjust the dosage of fluoride accordingly to the GFR and BSA.