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Chronotherapy of high-dose 1,25-dihydroxyvitamin D3 in hemodialysis patients with secondary hyperparathyroidism: a
S Tsuruoka1, K Sugimoto, M Ohmori
1Department of Clinical Pharmacology, Jichi Medical School, Minamikawachi, and Moka Hospital, Tochigi, Japan. tsuru@jichi.ac.jp
Background:
A high-dose oral intermittent vitamin D (pulse therapy) is widely used for the treatment of secondary hyperparathyroidism associated with kidney failure. However, hypercalcemia by vitamin D sometimes interrupts this treatment. Because serum calcium concentration possesses a circadian rhythm, a chronopharmacologic approach of vitamin D may have merit for avoidance of adverse reactions.
Methods:
Six female secondary hyperparathyroidism patients receiving maintenance hemodialysis received a single oral dose of 2 microg 1,25-dihydroxyvitamin D3 at either 8 AM or 8 PM in a crossover design. Serum concentrations of ionized and total calcium, phosphate, and vitamin D3 were determined for a 48-hour period after administration. We also measured serum intact parathyroid hormone before and 48 hours after dosing as an index for efficacy.
Results:
A single oral administration of the drug caused an increase in concentration of ionized calcium, serum calcium, and phosphate. However, the area under concentration-time curve from zero to 48 hours [AUC(0-48)] and peak concentration of these variables were markedly lower after dosing at 8 PM. Pre-dose concentrations of these variables were lower at night. The AUC(0-48) of serum vitamin D3 of the morning and night trials did not differ significantly. Reduction of intact parathyroid hormone concentration was also similar between the two trials.
Conclusion:
The administration of vitamin D3 at night may reduce the occurrence of hypercalcemia and hyperphosphatemia in patients with secondary hyperparathyroidism, whereas the pharmacokinetics and intact parathyroid hormone-lowering effect of the drug does not vary with dosing time.
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