Tiopronin is used together with diet, fluids, and other medicines to help prevent kidney stones in adults and children weighing at least 44 pounds (20 kilograms).

Tiopronin is usually given after diet, increased fluid intake, or other medications have failed.

Tiopronin may also be used for purposes not listed in this medication guide.

You should not use tiopronin if you are allergic to it.

This medicine should not be given to a child who is unable to swallow a tablet.

Tell your doctor if you are pregnant. It is not known whether tiopronin will harm an unborn baby. However, having a kidney stone during pregnancy may cause complications such as low birth weight or premature birth. The benefit of preventing kidney stones may outweigh any risks to the baby.

You should not breastfeed while using tiopronin.

Use Thiola EC (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives, rash; fever, swollen glands, joint pain; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have signs of kidney problems--puffy eyes, swelling in your ankles or feet, weight gain, or urine that looks foamy.

Common side effects may include:

• nausea, diarrhea, vomiting;
• feeling tired;
• fever;
• muscle or joint pain;
• foamy urine;
• rash; or
• mouth sores.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Avoid drinking alcohol 2 hours before and 3 hours after taking tiopronin.