Mineral density gain in vertebrae of osteoporotic women on oral pamidronate reverts a year after treatment discontinuance.

Long-term treatment with 200 mg dry weight/day of pamidronate (APD) by oral route has been proposed to increase bone mineral density (BMD) in postmenopausal osteoporotic women. However, there is widespread concern over the possibility of bone metabolism "freezing" by protracted use of medication liable to inhibit bone resorption. Accordingly, an open population of 39 osteoporotic women was studied in order to determine BMD variations in lumbar vertebrae and femoral neck and to confirm whether given APD doses increase bone mineralization. A parallel group of osteoporotic women was likewise evaluated to determine the potential reversibility of such effect on discontinuing treatment. Results were beneficial at both skeletal sites in subjects on APD therapy, disclosing at 18 months treatment 9.0% mean peak mineral gain versus basal status at lumbar spine. In the few responders completing 4 years of treatment, mean differences versus basal status were +4.9% in vertebrae and +6.2% at femoral neck. In lumbar vertebrae there was a rapid trend in mineral gain up to 18 months on treatment, which declined thereafter to a quarter of its early rate. Concurrently, in the group of 21 baseline-matched women, effects were evaluated after discontinuing daily APD administration one year (n = 11) or two years (n = 7) later. In both subgroups, there was a loss in lumbar (-7.1% and -9.8% respectively; p<0.01) and femoral neck BMD (-2.2% and -4.2% respectively; p: n.s.) on performing measurement one year after APD withdrawal. Furthermore, after three years treatment and subsequent discontinuance, three patients presented bone loss in lumbar vertebrae and minimal changes at femoral neck one year after APD withdrawal. Therefore, APD induces moderate BMD gain which proves reversible on discontinuing therapy, so that it seems unlikely that this compound should "freeze" bone metabolism to a significant extent. However, the precise degree of such reversibility requires evaluation in larger series.