The effect of prior bisphosphonate exposure on the treatment response to teriparatide in clinical practice

Our objective was to determine the effect of prior bisphosphonate exposure on the treatment response to teriparatide. All patients started on teriparatide in our hospital are entered into a database. All patients who had at least 12 months' treatment were identified. Patients were divided into two groups depending on whether or not they had prior bisphosphonate exposure, and the response to teriparatide was compared using procollagen of type 1 N-terminal propeptide (P1NP) and bone mineral density (BMD). Fifty-two patients had been treated for at least 12 months, 38 with prior bisphosphonate exposure and 14 without. The mean duration of bisphosphonate treatment was 67 months, discontinued a mean of 1 month previously. P1NP increased significantly at 3 and 6 months in both groups. However, those without previous bisphosphonate treatment had a higher baseline P1NP (49 vs. 30 microg/L, P<0.01), and this remained higher at 3 months (109 vs. 71 microg/L, P=0.10) and 6 months (183 vs. 126 microg/L, P=0.06), although the difference was not significant. In the prior bisphosphonate and bisphosphonate naive groups, respectively, the change in spinal BMD was 9.0% and 7.8% (P=0.54) at 12 months and 9.8% and 6.1% (P=0.30) at 18 months. The respective change in hip BMD was 1.0% and -0.3% (P=0.36) at 12 months and 2.8% and 1.3% (P=0.44) at 18 months. There was a trend toward a smaller but still significant increase in P1NP in response to teriparatide in bisphosphonate-treated patients. Although this suggests a blunting of the anabolic effects, in our clinic population this did not result in a reduction in BMD gain.