Effects of Teriparatide in Postmenopausal Women With Osteoporosis on Prior Alendronate or Raloxifene: Differences Between Stopping and Continuing the Antiresorptive Agent

Abstract

A number of studies have investigated combined use of anabolic therapy with teriparatide (recombinant human parathyroid hormone [PTH]) and antiresorptive therapy (alendronate or raloxifene) in postmenopausal women at high-risk of fracture, but the benefits are unclear due to conflicting results. This randomized, open-label trial investigated the effects of switching to teriparatide (Switch group) or adding this anabolic (Add group) on bone turnover markers (BTMs) and bone mineral density (BMD) in 198 postmenopausal women with osteoporosis who had been on alendronate or raloxifene for 18 months. Increases in BTMs were less in the alendronate Add group compared to the Switch group at 6 months: median increases in BTMs from baseline in the Add versus Switch group were 64% versus 401% for PINP; 15 versus 71% in bone ALP; and 27% versus 250% in ss-CTX (all P < 0.001). Total hip BMD increased more at 6 months with alendronate, however, in the Add versus Switch group (1.4% vs.-0.8%; P < 0.01). At 18 months, increases in BMD with alendronate were higher in the Add versus Switch group in the lumbar spine (8.4% vs. 4.8%; P < 0.003) and total hip (3.2% vs. 0.9%; P < 0.02). With respect to the raloxifene stratum, BTM data at 6 months were similar to those of the alendronate stratum in 2 respects. First, increases in the BTMs of the raloxifene stratum were also smaller in the Add than in the Switch group (131% vs. 259% in the PINP, P < 0.001; 31% vs. 44% in bone ALP, P < 0.035; and 67% vs. 144% in the ss-CTX, P < 0.001). Second, the total hip BMD increase was greater in the Add group (1.8% vs. 0.5%; P = 0.028). In contrast to alendronate, no significant differences between the groups were found at 18 months in lumbar spine (9.2% vs. 8.1%) or total hip BMD (2.8% vs. 1.8%). The between-group differences in femoral neck BMD were not significant in either stratum at 6 or 18 months. Adverse reactions and overall safety were similar in both groups. These findings show that in women with osteoporosis, switching to teriparatide produces greater increases in BTMs than adding this anabolic agent to an antiresorptive, whereas adding confers greater increases in BMD.