Abstract
The protein binding rate of the active vitamine D3, calcitriol, was evaluated using sera from 6 normal healthy subjects (HS) and 6 patients with chronic renal failure (CRF).
The binding rates of calcitriol at a concentration of 50pg/ml were 97.93±0.18%, 98.03±0.25% and 97.30±0.19% for sera from HS, patients receiving conservative treatment (ND) and those receiving hemodialysis (HD), respectively. The binding rates at a concentration of 200pg/ml were 96.11±0.56%, 96.28±0.42% and 95.11±0.89% for sera from HS, ND and HD patients, respectively. Thus, the protein binding rate of calcitriol was somewhat lower at a concentration of 200pg/ml than at 50pg/ml in all subject groups. However, no significant difference was seen in the protein binding rate between the two concentrations in any of the subject groups.
The binding rates of calcitriol at a concentration of 50pg/ml were 97.30±0.19% and 97.27±0.59% for sera before and after HD, respectively. At a concentration of 200pg/ml, rates were 95.11±0.89% and 95.10±0.47% for sera before and after HD, respectively. There were no significant differences among these values.
In evaluating the metabolic fate of drugs, careful consideration should be given to changes in their protein binding rate. However, our results showed little difference in the protein binding rate of calcitriol between HS and CRF patients, suggesting that the total calcitriol concentration can be used as an indicater in evaluating the disposition of calcitriol in CRF patients, without considering changes in its protein binding rate.
