Thiola EC represents several modifications of Thiola that promise better, more efficacious therapy of cystinuria. First, pill size has changed from 100 mg to 300 mg, meaning that typical pill burden will be reduced from, on average, 10 pills per day to 3-5 pills per day. This change will be welcomed by patients whose fluid intake and administration of potassium citrate are daily impositions. Second, the preparation is now enteric-coated, formulated to offer delayed release of active tiopronin. Lastly, Thiola EC can be taken with food which is an improvement to the inconvenient dosing regimen of Thiola, which can only be taken one hour before, or two hours after meals. These changes may affect compliance and side effect profiles compared to those of Thiola. In combination with potassium citrate or other alkali preparations, adverse GI effects are relatively common in actively-treated patients with cystinuria. It is possible that GI side effects may be reduced by Thiola EC.

Inclusion Criteria:

1. 18 years of age or older
2. Patients with cystinuria and a history of kidney stones
3. Taking Thiola EC
4. Willing and able to provide consent

Exclusion Criteria:

1. Unable to sign informed consent.

Patients with cystinuria on Thiola EC.

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices) will be shared upon reasonable request.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data, researchers who provide a methodologically sound proposal, and investigators whose proposed use of the data has been approved by an independent review committee ("learned intermediary") identified for this purpose will have access to the data upon reasonable request. Requests should be directed to david.goldfarb@nyulangone.org. To gain access, data requestors will need to sign a data access agreement.