Fluoride treatment of osteoporosis: Cyclical non-blinded or continuous blinded studies?

Abstract

The future of sodium fluoride (NaF), the most potent osteoblast stimulator known to man, is in the balance. Of three recent randomized trials of continuous NaF only one found a significant invertebral fractures in the NaF group. When data from the first year were excluded, two of the studies (those with the largest numbers) showed a significantly reduced risk of vertebral fracture on NaF. The effect of NaF oncortical bone is poorly documented. Two studies have shown reduced forearm cortical bone density with continuous NaF. A further two (histomorphometric) studies have shown the development of increased cortical porosity on continuous NaF treatment. In one, this was selectively at the external cortex and was linearly correlated with cancellous volume increase. Our pilot study using NaF administeredcyclically has shown an encouraging (though non-significant) reduction in vertebral fracture rates (excluding year 1) and no fall in forearm cortical density. Another (US) cyclical study has shown no increase in cortical porosity. A current W. Australian randomized study of 50 patients is described where NaF dosage is varied proportional to the osteoblast response, and duration is dependent on densitometric and radiographic response. The future of NaF should involve cyclical administration, in cautious initial dosage (50–60 mg/day) of enteric-coated NaF, in conjunction with apotent inhibitor of resorption such as hormone replacement, bisphosphonates or calcitonin.