Effect of Increasing Doses of Tiopronin on Cystine Capacity in Patients With Cystinuria
Effect of Increasing Doses of Tiopronin on Cystine Capacity in Patients With Cystinuria
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