Lack of effect of ipriflavone on osteoclast motility and bone resorption in in vitro and ex vivo studies.

Using in vitro and ex vivo experimental procedures specifically designed to visualize pharmacological effects on parameters of bone resorption, studies were performed to elucidate whether ipriflavone's reported effect in osteoporosis is due to an effect on the motility and resorptive activity of osteoclasts, as has been shown to be the case with salmon calcitonin. Concentrations of ipriflavone used were higher by a factor of > 100 than peak blood levels measured in patients given standard therapeutic doses. Despite this, neither quantitative nor qualitative changes were observed in the motility of isolated rat osteoclasts or in their resorptive activity when incubated with bone slices. The conclusion is that ipriflavone does not possess antiosteoclastic and antiresorptive activity of the type documented for salmon calcitonin in the models employed and that further investigation of its mode of action is therefore necessary.