Determining Oral Phosphate Tolerance Across the Spectrum of Glomerular Filtration Rate

Over 20 million people in North America (including 2 million Canadians) have chronic kidney disease. These individuals die from diseases of the heart and blood vessels more often than they need dialysis. This is due to hardening of the arteries caused by calcium deposits inside the blood vessel walls. These deposits damage the vessels, causing them to lose flexibility. This makes them unable to respond to the changing demands of the body, and eventually leads to blockages such as stroke and ultimately death.

High levels of phosphate in the blood have been consistently linked to the development of calcium deposits inside blood vessel walls. The kidney is the only organ in the body that can eliminate phosphate that is not required by the body. As kidney function becomes worse, body levels of phosphate increase. However, investigators do not know the time point in the course of kidney disease that problems begin in the way phosphate is eliminated into the urine by the kidneys. Investigators will test the response of the kidneys to a phosphate challenge taken by mouth in subjects who are having accurate measures of kidney function performed by a method called 'inulin clearance'.

The investigators believe that the results of this study will provide important information identifying when investigators should be concerned about body levels of phosphate increasing. This information may lead to changes in the way investigators treat patients by reducing the levels of phosphate in the diet at a much earlier time point then is presently recommended.

Study Overview

• Status: Completed
• Conditions: Chronic Kidney Disease
• Intervention / Treatment: Drug: Phoslax

Detailed Description

Fractional excretion of phosphate will be measured pre- and 60 minutes and 120 minutes following an oral challenge of 500 mg of oral phosphate in a group of patients with gold standard measures of glomerular filtration rate.

• Study Type: Interventional
• Enrollment (Actual): 78
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Kingston, Ontario, Canada, K7L 3N6
      • Kingston General Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• stable chronic kidney disease

Exclusion Criteria:

• unable/unwilling to give informed consent;
• pregnant or breast-feeding;
• known allergy to shellfish, iodine or inulin;
• have evidence of impaired bladder emptying defined as a post-void residual of greater than 20 ml.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Phosphate; 500 mg of oral phosphate is administered after an overnight fast.	Drug: Phoslax; Oral sodium phosphate solution (monobasic sodium phosphate 2.4 g and dibasic sodium phosphate 0.9g / 5 mL).; Other Names: Sodium Phosphate

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fractional excretion of phosphate	Fractional excretion of phosphate will be measured at baseline and at 1 and 2 hours following a standardized oral phosphate challenge	Change in fractional excretion of phosphate at 1 and 2 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fibroblast growth factor-23	Biomarker of phosphate homeostasis	Change in level of fibroblast growth factor 23 at 2 hours
Vitamin D	Biomarker of phosphate homeostasis	Change in level of vitamin D and vitamin D metabolites at 2 hours
klotho	Biomarker of phosphate homeostasis	Change in level of circulation kloth at 2 hours

Collaborators and Investigators

• Sponsor: Dr. Rachel Holden
• Investigators: Study Chair: Rachel M Holden, MD, Queen's University

Study record dates

Study Major Dates

• Study Start: January 1, 2013
• Primary Completion (Actual): April 18, 2018
• Study Completion (Actual): April 18, 2018

Study Registration Dates

• First Submitted: January 16, 2013
• First Submitted That Met QC Criteria: February 2, 2016
• First Posted (Estimate): February 3, 2016

Study Record Updates

• Last Update Posted (Actual): July 5, 2022
• Last Update Submitted That Met QC Criteria: June 29, 2022
• Last Verified: June 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Urologic Diseases; Renal Insufficiency; Kidney Diseases; Renal Insufficiency, Chronic
• Other Study ID Numbers: Holden/White; Queen's University (Other Identifier: Queen's University)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No