The purpose of this study is to determine the minimum effective dose of the cysteine binding thiol drug (CBTD) Tiopronin on urine cystine capacity, which is a measure of cystine solubility in the urine, in patients with cystinuria to evaluate the effect of escalating doses of cystine binding thiol drugs on the cystine capacity of the urine. The overall goal will be to help guide therapy and ultimately minimize unnecessary side effects caused by larger dosages.

Cystinuria is a rare genetic disease that can lead to significant morbidity in affected patients due to the recurrent nature of the disease. This study will follow the levels of urine cystine capacity in order to help guide treatment and to use lower than usually prescribed Tiopronin doses to decrease the potential side effects while maintaining therapeutic benefit. This will increase adherence with the medications by decreasing the burden of the large number of pills that need to be taken daily.

Inclusion Criteria:

• Patients with a confirmed laboratory diagnosis of cystinuria who meet the following criteria: (1) stone analysis demonstrating cystine as a component, or (2) increased urinary cystine excretion (>250mg/24hrs in adults).
• A medical regimen that includes Tiopronin.
• Willing to use a medically accepted form of birth control, if female and of child bearing- potential
• Ability to reliably urinate in a collection vessel and measure urine volume.
• Ability to give informed consent.
• Documentation of a stable complete blood count (CBC) and urinalysis (UA) in the six month period prior to the date of enrollment.
• Enrollment in Rare Kidney Stone Consortium (RKSC) Protocol 6401 (Cystinuria Registry)

Exclusion Criteria:

• Women who are pregnant, breastfeeding, or trying to become pregnant
• Patients with renal colic
• Patients who are scheduled to undergo a surgical procedure
• Inability to give informed consent

All of the individual participant data collected during the trial, after deidentification. Researchers who provide a methodologically sound proposal.

Beginning 9 months and ending 36 months following article publication.

Proposals may be submitted up to 36 months following article publication. After 36 months the data will be available in our University's data warehouse but without investigator support other than deposited metadata. Information regarding submitting requests and accessing data may be found at (Link to be provided

Multiple efforts to contact the PI/study team for the relevant data have failed. Therefore, per intervention data are not available to be reported for this assessment.

30 days

Multiple efforts to contact the PI/study team for the relevant data have failed. Therefore, per dose level data are not available to be reported for this assessment.