Effects of teriparatide in postmenopausal women with osteoporosis on prior alendronate or raloxifene: Differences between stopping and continuing the antiresorptive agent

Objective: The aim of the study was to assess adding vs. switching to teriparatide 20μg/d in patients on alendronate or raloxifene. Design: We conducted a randomized, open-label trial. Patients and Interventions: Postmenopausal women with osteoporosis on alendronate or raloxifene for at least 18 months added teriparatide (Add groups) or switched to teriparatide (Switch groups) for 18 months. Main Outcome Measures:Wemeasured bone turnover markers (BTM) and bone mineral density (BMD). Results: In the alendronate stratum, increases in BTM were smaller in the Add vs. Switch group [6-month PINP (64 vs. 401%); bone ALP (15 vs. 71%); βCTX (27 vs. 250%); all P < 0.001]. However, at 6 months, total hip BMD increased more in the Add vs. Switch group (1.4 vs. -0.8%; P = 0.002). In the Add vs. Switch group, 18-month BMD increments were higher in lumbar spine (8.4 vs. 4.8%; P = 0.003) and total hip (3.2 vs. 0.9%; P = 0.02), but not in femoral neck (2.7 vs. 2.3%; P = 0.75). In the raloxifene stratum, increases in BTM were also smaller in the Add vs. Switch group [6-month PINP (131 vs. 259%; P<0.001), bone ALP (31 vs. 44%; P=0.035), and βCTX (67 vs. 144%; P=0.001)]. At 6 months, total hip BMD increase was greater in the Add vs. Switch group (1.8 vs. 0.5%; P = 0.028). At 18 months, increases in lumbar spine (9.2 vs. 8.1%), total hip (2.8 vs. 1.8%), and femoral neck (3.8 vs. 2.2%) were not significantly different between groups. Conclusions: In women with osteoporosis treated with antiresorptives, greater bone turnover increases were achieved by switching to teriparatide, whereas greater BMD increases were achieved by adding teriparatide.