Cystone will be used in proven cystine and calcium stone forming adults who are not pregnant. Subjects must have a measurable stone by CT. The first phase is a double blind, randomized, placebo controlled cross-over of Cystone and placebo for 6 weeks each separated by a 1 week washout. Entry, 6 and 12 week 24 hour urine supersaturations or cystine, pH and sodium determinations will be collected. Then all patients enter an open label phase of 46 weeks, ensuring a 52-week total exposure to Cystone during the 59 week study. Baseline and 1 year stone quantification CT scans will be performed. End points will be changes in urine chemistry/supersaturation and stone burden. Stone burden was measured by CT, quantitatively for stone density and volume. All CT images were also reviewed in a blinded fashion by a radiologist to score each kidney as increased, no change or decreased stone burden.
Statistics and Randomization: Randomization was accomplished using a table provided by the department of statistics to the study coordinator who was blinded as to whether the patients received placebo or Cystone®. Biochemical and supersaturation results were analyzed via a matched pair analysis using the JMP software package (SAS Instituted, Inc.); P values < 0.05 were deemed significant.
- Written informed consent In the cystine arm, all patients will have the diagnosis of cystinuria, made on the basis of a 24-hour urine cystine containing more than 1500 umol of cystine, or a stone compositional analysis of cystine
- Presence of an existing cystine stone in one or both kidneys In the calcium arm, all patients will have a history of a calcium stone as determined by laboratory analysis.
- Medically effective birth control if fertile female
- Able to comply with protocol
- Subjects under age 18 years
- Obstructing stones
- Urinary Tract Infection that cannot be cleared with single course of antibiotic
- Subjects who decline to provide informed consent
Patients who choose to participate in this research study will begin by having an x-ray (CT scan) of their kidneys, giving a blood sample in the amount of approximately two teaspoons, and submitting two 24-hour urines collected while they are eating their typical diet and drinking their usual beverages. These studies would normally be done as part of a standard kidney stone evaluation. Then, the calcium-containing kidney stone formers and the cystine kidney stone formers will be randomly assigned to take either Cystone in the amount of 3 tablets two times daily or an identical placebo (inactive pill) for six weeks. The group you start in will be determined by chance (as in the flip of a coin). At the end of the first six weeks, two more 24-hour urines are collected on usual diet and fluids. These can be collected at home and mailed to Mayo Clinic laboratories or returned in person. Next, the patients who were taking Cystone will cross over to placebo and the patients taking placebo will switch to Cystone for another six weeks. Neither the researchers nor the patients will know which pills are Cystone and which are placebo. At the end of the second six-week period, two more 24-hour urine samples are collected on the patient?s usual diet and fluid consumption. These may also be returned to Mayo Clinic laboratories by mail or delivered in person. After this, all patients will receive Cystone in the same dose as before for 46 consecutive weeks. At the end of 46 weeks, each patient must return to Mayo Clinic for a repeat CT scan, a repeat blood sample of approximately 2 teaspoons, and two repeat 24-hour urine collections on usual diet and fluid consumption, as would be done at a standard one-year kidney stone follow-up appointment that was not part of a research study. Thus, each patient who enrolls in this research study will be assured of receiving 52 weeks of Cystone and six weeks of placebo treatment. At the end of the study, you must return any unused Cystone.
You will be in the study for 58 weeks plus a one-week period of time off treatment (washout) between the six-week placebo and six-week Cystone treatment periods to allow the medication to leave your body.
Last updated: 06/12/2012
NCT ID: NCT00381849