Sevelamer and Secondary Hyperparathyroidism in Chronic Kidney Disease
NCT ID: NCT01191762
Last Updated: 2016-11-01
Study Results
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View full resultsBasic Information
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COMPLETED
PHASE3
30 participants
INTERVENTIONAL
2010-04-30
2013-04-30
Brief Summary
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Detailed Description
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We hypothesize that phosphate exerts its effect on \[PTH\] in the cortical distal nephron (CDN). Ordinarily, intestinal phosphate absorption does not fall in proportion to GFR as chronic kidney disease (CKD) progresses. Consequently, the concentration of phosphate increases in the cortical distal nephron (CDN), where PTH regulates tubular calcium reabsorption. We speculate that increased \[P\]cdn reduces the concentration of free calcium through complexation, and thereby necessitates high \[PTH\] for achievement of calcium reabsorption sufficient to maintain normocalcemia. We can show algebraically that \[P\]cdn is proportional to the ratio EP/Ccr, where EP is the urinary excretion rate of phosphate and Ccr is creatinine clearance, a surrogate for GFR. EP/Ccr can be calculated from measurements in aliquots of serum and urine as \[P\]u\[cr\]s/\[cr\]u. If our hypothesis is correct, we anticipate that \[PTH\] will be proportional to EP/Ccr in CKD, and that delta \[PTH\] will be proportional to delta EP/Ccr obtained with sequential determinations.
We will study 30 patients with CKD and a comparable number of controls. All subjects will have normocalcemia. Controls will be seen once for informed consent, and once in the fasting state between 8:00 a.m. and 10:00 a.m. for collection of urine and blood specimens.
Patients with CKD will be seen at five visits at intervals of four weeks. At the first visit, we will obtain informed consent and obtain a specimen for measurement of 25-hydroxyvitamin D (25OHD). At visits 2-5, we will obtain necessary specimens to measure concentrations of PTH, fibroblast growth factor 23 (FGF23), 25OHD, and 1,25-dihyroxyvitamin D (1,25(OH)2D). We will also measure ionized and ultrafilterable calcium, creatinine, and phosphorus in serum and calcium, phosphorus, and creatinine in urine. These measurements will enable us to follow the effects of interventions on hormone concentrations and parameters of calcium and phosphorus homeostasis.
At visit 2 we will prescribe vitamin D in accordance with \[25OHD\] obtained at visit 1. For \[25OHD\] \< 32 ng/mL, doses will be 50,000 units/d of D2 for one week, followed by 2000 mg/d of D2 for 3 weeks. For \[25OHD\] \> 32 ng/mL, the dose will be D3 2000 mg/d for four weeks. The purpose of this intervention is to minimize the likelihood that vitamin D insufficiency or deficiency contributes to SHPT.
At visit 3, we will instruct patients in a phosphate-restricted diet. At visit 4 we will quantify the metabolic effects of the diet, and will randomly assign patients to receive either placebo or sevelamer carbonate 800 mg tablets, 3 with each meal. At visit 5, we will quantify the effects of the two interventions on parameters of calcium and phosphate homeostasis and on hormone concentrations. We will view positive regressions of \[PTH\] on EP/Ccr and of ∆\[PTH\] on ∆EP/Ccr as evidence for our hypothesis.
Conditions
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Keywords
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Study Design
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RANDOMIZED
PARALLEL
TREATMENT
QUADRUPLE
Study Groups
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sevelamer carbonate
2400 mg (3 pills) with each meal
sevelamer carbonate
2400 mg with each meal for 4 weeks
placebo control
3 placebo tablets with each meal; tablets are identical to sevelamer carbonate 800 mg tablets.
placebo
3 tablets with each meal
Interventions
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sevelamer carbonate
2400 mg with each meal for 4 weeks
placebo
3 tablets with each meal
Other Intervention Names
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Eligibility Criteria
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Inclusion Criteria
* age at least 18 years
Exclusion Criteria
18 Years
120 Years
ALL
Yes
Sponsors
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Genzyme, a Sanofi Company
INDUSTRY
Kenneth R. Phelps, M.D.
INDIV
Responsible Party
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Kenneth R. Phelps, M.D.
Principal Investigator
Principal Investigators
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Kenneth R. Phelps, M.D.
Role: PRINCIPAL_INVESTIGATOR
Stratton VAMC, Albany, NY
Locations
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Stratton Veterans Affairs Medical Center
Albany, New York, United States
Countries
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References
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Natale P, Green SC, Ruospo M, Craig JC, Vecchio M, Elder GJ, Strippoli GF. Phosphate binders for preventing and treating chronic kidney disease-mineral and bone disorder (CKD-MBD). Cochrane Database Syst Rev. 2025 Jun 27;6(6):CD006023. doi: 10.1002/14651858.CD006023.pub4.
Phelps KR, Mason DL. Parathyroid Hormone, Fibroblast Growth Factor 23, and Parameters of Phosphate Reabsorption. Am J Nephrol. 2018;47(5):343-351. doi: 10.1159/000489270. Epub 2018 May 18.
Phelps KR, Mason DL, Stote KS. Phosphate homeostasis, parathyroid hormone, and fibroblast growth factor 23 in stages 3 and 4 chronic kidney disease. Clin Nephrol. 2016 May;85(5):251-61. doi: 10.5414/CN108686.
Phelps KR, Mason DL. Parameters of phosphorus homeostasis at normal and reduced GFR: theoretical considerations. Clin Nephrol. 2015 Mar;83(3):167-76. doi: 10.5414/cn108367.
Other Identifiers
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PhelpsK
Identifier Type: -
Identifier Source: org_study_id