Effect of long-term treatment with strontium ranelate on bone strontium content.
OBJECTIVE
To investigate the kinetics and magnitude of human bone strontium uptake and retention during and after long-time treatment with strontium ranelate (SrR).


METHODS
Bone strontium was measured by a novel DPA method developed by us. 32 osteoporotic female patients volunteered to participate in a 3 years open study of the effect on bone Sr. The group was treated with 2 g SrR/day, 17 of the group had received active treatment for 4-5 years before the study. DXA BMD measurements and DPA measurements of the relative bone strontium hydroxy apatite termed %Sr (SrHA/(CaHA+SrHA)) were done simultaneously ultra-distally (UD) on the non-dominant radius every six months during the study and three and six months after treatment stop.


RESULTS
The highest relative Sr content was found in patients who had been treated for 7-8 years. The variability was pronounced; a mean of 1.1 % Sr was measured at the end of treatment. No effect was demonstrated on distal radius relative bone Ca hydroxy apatite. Bone strontium uptake and retention data were compatible with a power function model. Withdrawal of SrR resulted in a decline in bone Sr, but 73 %Sr and 67 %Sr, respectively remained in UD-radius three and six months after drug withdrawal.


CONCLUSIONS
The rise in bone Sr content measured by DPA as well as BMD measured by DXA was most marked initially. After the treatment was stopped bone Sr decreased rapidly only during the first months. In UD-radius the apparent BMD corrected for the influence of %Sr measured by DPA showed a slight decline like in an untreated population. Strontium containing drugs may influence DXA bone mineral measurements several years after treatment withdrawal. According to the power function model the skeletal retention three and six months after stopping the treatment would average 66% and 58%, respectively after three years of treatment, and 76% and 70%, respectively after eight years of treatment. However, individual predictions are uncertain due to large inter-individual variations, and the values cannot be extrapolated to other bone sites.
Bone Unit, Department of Clinical Physiology, Hillerød Hospital, DK-3400 Hillerød, Denmark.
Olaf
O
Bärenholdt
Niels
N
Kolthoff
Stig Pors
SP
Nielsen
D015502:Absorptiometry, Photon; D000369:Aged, 80 and over; D015519:Bone Density / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D006801:Humans; D009942:Organometallic Compounds / Q000494:pharmacology*; D011884:Radius / Q000187:drug effects / Q000378:metabolism; D013324:Strontium / Q000378:metabolism*; D013876:Thiophenes / Q000494:pharmacology*; D013997:Time Factors
D009942:Organometallic Compounds; D013876:Thiophenes; C081587:strontium ranelate; D013324:Strontium