Ipriflavone: pharmacological properties and usefulness in postmenopausal osteoporosis

Ipriflavone (IP) is an isoflavone derivative available in several countries for investigational and/or therapeutic use. Inhibition of bone resorption was demonstrated in several models, both in vitro and in vivo for IP and its metabolites. Their mechanisms of action on bone are not yet fully elucidated but some of them are widely accepted. IP does not possess, per se, any estrogenic activity. It appears that IP-related inhibition of bone resorption might be mediated by an indirect effect on osteoclast and related to an inhibition of recruitment and/or differentiation of pre-osteoclast, maybe through a modulation of osteoblast response to PTH. Clinical studies in Paget's disease of bone or primary hyperparathyroidism have confirmed preferential inhibition of bone resorption suggesting a clinical interest in postmenopausal osteoporosis. Preliminary (1 year) results of double blind placebo controlled studies designed in postmenopausal and senile osteoporosis confirm a reduction in bone turnover rate in patients treated with 600 mg/day of IP, resulting in a significant bone-sparing effect both at lumbar and radial levels. All clinical and pharmacological trials confirm a very good tolerance of IP with a frequency of adverse reactions equal to that observed during administration of a placebo. Providing ongoing studies will confirm the actual promising preliminary results, IP seems a very interesting new non hormonal approach for prevention and treatment of postmenopausal and senile osteoporosis.