Introduction- EUROFORS was a two-year prospective, randomized trial of postmenopausal women with established osteoporosis, designed to investigate various sequential treatments after teriparatide 20 µg/day for one year. The present secondary analysis examined the effects of two years of open-label teriparatide in women previously treated with antiresorptive drugs for at least one year.

Methods- A subgroup of 245 women with osteoporosis who had two years of teriparatide treatment were stratified by prior predominant antiresorptive treatment into 4 groups: alendronate (n = 107), risedronate (n = 59), etidronate (n = 30), non-bisphosphonate (n = 49). Bone mineral density (BMD) at the lumbar spine and hip was determined after 6, 12, 18, and 24 months, and bone formation markers were measured after 1 and 6 months.

Results- Significant increases in bone formation markers occurred in all groups after 1 month of teriparatide treatment. Lumbar spine BMD increased at all visits, while a transient decrease in hip BMD, that was subsequently reversed, was observed in all groups. BMD responses were similar in all prior antiresorptive groups. Prior etidronate users showed a higher increase at the spine but not at the hip BMD. Duration of prior antiresorptive therapy and lag time between stopping prior therapy and starting teriparatide did not affect the BMD response at any skeletal site. Treatment emergent adverse events were similar to those reported in treatment naïve postmenopausal women with osteoporosis treated with teriparatide.

Conclusions- Teriparatide induces positive effects on BMD and markers of bone formation in postmenopausal women with established osteoporosis, regardless of prior long-term exposure to antiresorptive therapies.