Clearance of 25-hydroxyvitamin D in Cystic Fibrosis

University of Washington10 enrolled

Overview

The goal of this study is to define 25(OH)D3 catabolism in CF patients using gold standard pharmacokinetics studies. Specifically, the investigators will evaluate the metabolic clearance of 25(OH)D3 among participants with CF and matched control subjects. The goal of this work is to provide the first comprehensive characterization of vitamin D metabolism in CF patients and promote novel hypotheses for subsequent studies.

Study Type

INTERVENTIONAL

Allocation

Purpose

DIAGNOSTIC

Masking

NONE

Enrollment

Conditions

Cystic Fibrosis

Interventions

d6-25-hydroxyvitamin D3DRUG

intravenous administration of stable isotope-labeled D6-25(OH)D3

Eligibility

Sex: ALLMin age: 18 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Age ≥ 18 years * Serum total 25(OH)D 10-50 ng/mL * Diagnosis of cystic fibrosis in accordance with CF Foundation Guidelines; OR, normal CONTROL Exclusion Criteria: * Primary hyperparathyroidism * Gastric bypass * Tuberculosis or sarcoidosis * Current pregnancy * Child-Pugh Class B or C cirrhosis (i.e. cirrhosis with ascites, hepatic encephalopathy, bilirubin \>=2 mg/dL, serum albumin \<=3.5 g/dL, or PT \>= 4 seconds) * History of kidney transplantation or end stage renal disease treated with dialysis * Use of vitamin D3 or vitamin D2 supplements exceeding a mean daily dose of 400 IU, within 3 months (wash-out allowed) * Use of 1,25(OH)2D3 or an analogue, calcimimetics, or medications known to induce CYP24A1 within 4 weeks (wash-out allowed) * Serum calcium \> 10.1 mg/dL * Hemoglobin \< 9 g/dL

Locations (1)

University of Washington

Seattle, Washington, United States

Outcomes

Primary Outcomes

Metabolic Clearance of D6-25(OH)D3

Metabolic clearance is calculated as the administered dose of 25(OH)D3 divided by the area under the plasma concentration-time curve (AUC). AUC is calculated using the linear trapezoidal method.

Time frame: 8 weeks

Secondary Outcomes

AUC of D6-25(OH)D3

AUC is calculated using the linear trapezoidal method.

Time frame: 8 weeks

Terminal Half-life of D6-25(OH)D3

Terminal half-life is equal to ln2/k, where k is the slope of the terminal regression line estimated using ≥3 plasma concentrations.

Time frame: 8 weeks

Volume of Distribution of D6-25(OH)D3

Volume of distribution in the central compartment is calculated as dose/C0, where dose is the administered dose of 25(OH)D3 and C0 is the initial (estimated) concentration of drug in plasma.

Time frame: 8 weeks

Data from ClinicalTrials.gov

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