Impact of vitamin D dose on biochemical parameters in patients with secondary hyperparathyroidism receiving cinacalcet.
OBJECTIVE
The calcimimetic cinacalcet (Mimpara/Sensipar) simultaneously lowers parathyroid hormone (PTH), phosphorus (P) and calcium (Ca) levels in patients with secondary hyperparathyroidism. The OPTIMA study demonstrated that cinacalcet and adjusted doses of vitamin D maximized control of these parameters. This post-hoc analysis of OPTIMA data assessed the impact of reducing or increasing the dose of concomitant vitamin D on PTH, P and Ca in patients receiving cinacalcet.


METHODS
Dialysis patients with mean baseline intact PTH (iPTH) 300-800 pg/ml (31.8-84.8 pM) received doses of cinacalcet titrated to achieve an iPTH of 150-300 pg/ml (15.9-31.8 pM). The dose of vitamin D could then be decreased to further reduce serum P or Ca, or increased/initiated to further decrease PTH levels if iPTH >300 pg/ml or to increase Ca if Ca <8.0 mg/dl (2.0 mM).


RESULTS
Vitamin D dose was assessed for 345 patients during a 23-week period. A total of 91 and 129 patients had an increase or decrease in vitamin D dose, respectively. By study end, mean iPTH, P, and Ca were similar in both vitamin D groups, although there were differences in biochemical parameters between groups at the start of the study. There were statistically significant reductions from baseline to study end in iPTH and Ca in both groups (p < 0.001). Although P was significantly reduced by week 23 in the group in which vitamin D dose was decreased (p = 0.007), the reduction in P was less and did not achieve significance in the group in which vitamin D dose was increased (p = 0.71).


CONCLUSIONS
After initiating cinacalcet, the dose of vitamin D can be adjusted to maximize reductions in PTH, P and Ca; however, vitamin D-induced decreases in PTH need to be balanced with the diminished response in P and Ca.
Sheffield Kidney Institute, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK. martin.wilkie@sth.nhs.uk
Martin
M
Wilkie
Giuseppe
G
Pontoriero
Fernando
F
Macário
Magdi
M
Yaqoob
Koen
K
Bouman
Johann
J
Braun
Beat
B
von Albertini
Hans
H
Brink
Francisco
F
Maduell
Helmut
H
Graf
João M
JM
Frazão
Willem Jan
WJ
Bos
Vicente
V
Torregrosa
Heikki
H
Saha
Helmut
H
Reichel
Valter J
VJ
Zani
Dave
D
Carter
Piergiorgio
P
Messa
D000328:Adult; D002118:Calcium / Q000097:blood; D000069449:Cinacalcet; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000188:drug therapy / Q000209:etiology; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000188:drug therapy* / Q000209:etiology; D054559:Hyperphosphatemia / Q000188:drug therapy / Q000209:etiology; D007676:Kidney Failure, Chronic / Q000097:blood / Q000150:complications / Q000628:therapy; D008297:Male; D009281:Naphthalenes / Q000627:therapeutic use*; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000097:blood; D006435:Renal Dialysis; D014807:Vitamin D / Q000008:administration & dosage* / Q000494:pharmacology / Q000627:therapeutic use
D009281:Naphthalenes; D010281:Parathyroid Hormone; D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium; D000069449:Cinacalcet