Differential effects of paricalcitol and calcitriol on intestinal calcium absorption in hemodialysis patients.
OBJECTIVE
Increased parathyroid activity associated with chronic kidney disease is often managed with calcitriol, which can elevate serum calcium (Ca) by increasing bone resorption and intestinal absorption, whereas paricalcitol promotes less bone resorption. This study compared intestinal Ca absorption in hemodialysis patients treated with calcitriol versus paricalcitol (dose ratio 1:3).


METHODS
Patients (n = 22) aged > or =20 years, on maintenance hemodialysis for > or =2 months with intact parathyroid hormone (iPTH) levels of >200 pg/ml were enrolled in a single-center, double-blind, active-controlled, randomized, crossover trial. Mean fractional intestinal Ca absorption (+/-SE) was measured by the single-tracer method ((42)Ca) and evaluated with an analysis of variance crossover model.


RESULTS
Mean fractional intestinal Ca absorption was significantly lower after paricalcitol (0.135 +/- 0.006) versus calcitriol treatment (0.158 +/- 0.006, p = 0.022), a 0.023 difference in absolute Ca absorption fraction. Overall Ca absorption was low in the study population, indicating that regulation of Ca absorption may be dysfunctional. There were no significant differences in serum PTH, Ca, phosphorus (P), or Ca x P.


CONCLUSIONS
Overall, paricalcitol-treated patients absorbed approximately 14% less Ca compared with calcitriol-treated patients with similar effects on PTH. In hemodialysis patients, paricalcitol may provide a benefit by lowering the Ca available for removal by dialysis and/or for deposit in bone or soft tissues.
Lund
Richard J
RJ
Department of Medicine, Creighton University, 3316 Dodge Street, Omaha, NE 68154, USA. RLund@creighton.edu
Andress
Dennis L
DL
Amdahl
Michael
M
Williams
Laura A
LA
Heaney
Robert P
RP
D000328:Adult; D002117:Calcitriol / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D018592:Cross-Over Studies; D004872:Ergocalciferols / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D006801:Humans; D007422:Intestines / Q000187:drug effects; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D006435:Renal Dialysis; D016896:Treatment Outcome
D004872:Ergocalciferols; D010281:Parathyroid Hormone; D010758:Phosphorus; C084656:paricalcitol; D002117:Calcitriol; D002118:Calcium