Buffering effects of calcium carbonate as clarified by sevelamer hydrochloride monotherapy.

This study was undertaken to examine the necessity of taking into account the acid-base balance to ensure safe switching from calcium carbonate to sevelamer hydrochloride in hemodialysis patients. Forty-two hemodialysis patients were divided into two groups: the sevelamer hydrochloride therapy group (n = 18; "monotherapy group") and the combined calcium carbonate plus sevelamer hydrochloride therapy group (n = 24; "combined therapy group"). Observation was continued for six months. Subsequently, treatment with calcium carbonate was resumed in the monotherapy group at a dose level equal to that used before the start of study, and the combined therapy group continued to receive combined calcium carbonate + sevelamer hydrochloride therapy for another six months. The monotherapy group showed marked metabolic acidosis (HCO(3)(-) level from 20.2 +/- 2.4 mmol/L to 17.7 +/- 0.5 mmol/L). While the acidosis also became worse in the combined therapy group, the decrease in serum HCO(3)(-) level was smaller in this group than in the monotherapy group. The monotherapy group showed rapid recovery from acidosis following resumption of calcium carbonate administration (HCO(3)(-) level from 17.7 +/- 0.5 mmol/L to 20.6 +/- 0.7 mmol/L). We analyzed the cause of acidosis by the Stewart-Figge approach, and it was found to be attributable to the elevation of the serum Cl(-) level. The results suggest that treatment with calcium carbonate shows some buffering effects. Calcium carbonate acts as a potent alkalizing agent. We therefore consider it advisable to use sevelamer hydrochloride in combination with calcium carbonate in hemodialysis patients.

[Treatment with phosphate binder (sevelamer hydrochloride, calcium carbonate) based on PTH].

When sevelamer hydrochloride is used as a phosphate binder instead of the more common calcium carbonate, the PTH rises. This has been observed in many cases and makes it more difficult for practical use. However, considering the calcium load, the excessive dosing of calcium carbonate must be avoided. With that in mind, we divided the i-PTH in groups of 100 pg/mL and tested the changes in i-PTH value, P value, the adjusted Ca value, and the product of Ca and P before and after a dosage of sevelamer hydrochloride. When the average i-PTH was under 100mg/mL 6 months before dosing, the sevelamer hydrochloride single dosage group showed an early rise in i-PTH after dosing, maintaining a higher level than the calcium carbonate combined dosage group. Therefore, it was concluded that the use of sevelamer hydrochloride alone as a phosphate binder is best. On the other hand, the group with an average i-PTH over 100 pg/mL 6 months before dosing showed a rise of i-PTH that went over the K/DOQI guideline with a single dosing of sevelamer hydrochloride. Therefore, we concluded that using both sevelamer hydrochloride and calcium carbonate for phosphate binder is best.

[Relationship between serum calcium level and PTH concentration proved with sevelamer hydrochloride].

About a dialysis patient's calcium-phosphate (Ca.P) metabolism, in general good control is obtained by use of sevelamer hydrochloride. As for this, what is significantly depended on not only lower P concentration but also lower Ca concentration by the change to sevelamer hydrochloride from calcium carbonate. However, by one side, much rises of i-PTH are observed by most patients with change to sevelamer hydrochloride. In this examination, Deltai-PTH was intentionally correlated with Delta calcium concentration but there was no correlation in i-PTH and Ca concentration.