The bisphosphonate ibandronate, given daily as well as discontinuously, decreases bone resorption and increases calcium retention as assessed by 45Ca kinetics in the intact rat.

The new bisphosphonate ibandronate was given at various doses and regimens to normal growing rats, and its effect on calcium metabolism investigated by means of 45Ca kinetics. The bisphosphonate began to inhibit bone resorption at a dose of 0.1 microgram P/kg, given daily. At higher doses intestinal calcium absorption, calciuria and calcium balance were also increased, calcemia being decreased. There was no difference in effect when the same amount of compound was given either daily for 10 days or all at once. Furthermore, the effect of a high dose of 100 micrograms P/kg was present 1 month after a single administration, whereas a dose 10 times lower was no longer effective. These results suggest that ibandronate may be effective in humans for decreasing bone resorption and increasing calcium balance in osteoporosis, when given either daily or discontinuously.