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

Abstract

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: We measured 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. In patients treated with alendronate or raloxifene, adding teriparatide results in a greater bone mineral density response, and appears to be at least as safe as switching to teriparatide.