Llach F, Hervas J, Cerezo S
The importance of dosing intravenous calcitriol in dialysis
patients with severe hyperparathyroidism
Am J Kidney Dis
(Nov) 26:845-851 1995
These investigators studied the response of 10 dialysis patients
with very severe hyperparathyroidism (intact-PTH = 1826 +/- 146 pg/ml;
normals < 65). They used very high doses of calcitriol (up to 6.0 mcg
IV three
times a week) and achieved striking results (mean PTH at end of study was
211 +/- 48). Initial vitamin D dose was determined by the height of
the initial
PTH level and subsequent dose adjustments were made based on the PTH
response. If PTH did not decline
after 1 to 2 weeks, the dose of calcitriol was increased. When PTH declined
by 25-30%, the calcitriol dose was decreased. By the end of the study
(48 weeks) PTH was
down approximately 90% while the calcitriol dose remained at 1.2 mcg after
each dialysis. The authors noted hyperphospahtemia and hypercalcemia
rarely and attributed this to careful diet monitoring, low calcium
dialysate (2.5 mEq/L) and use of calcium acetate. They contrasted their
results
to that of Rao Sudhaker, et al (study in press) in which phosphate
control was not so good and in which the PTH response was much poorer.
Comment: This last point is both the strength and weakness
of the study. Much
recent data confirm the necessity for good phosphate control to achieve
PTH control. The unresolved question is how to achieve this.
For many patients in this state, such good phosphate control is not
possible (that is why they got into trouble in the first place) and
hyperphosphatemia limits the use of calcitriol therapy.
If phosphate can be controlled as well as
Llach et al have done in this study, most of us should see similar
responses. In my own experience, this degree of control
is very difficult to achieve in most such patients.
(Sherrard)
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