For Health Professionals

The role of Thiola^® in treatment

Thiola^® is indicated for the prevention of cystine (kidney) stone formation in patients with severe homozygous cystinuria with urinary cystine greater than 500 mg/day, who are resistant to treatment with conservative measures of high fluid intake, alkali and diet modification, or who have adverse reactions to d-penicillamine. The goal of therapy is to reduce urinary cystine concentration below its solubility limit.

Thiola^® is an active reducing agent that undergoes thiol-disulfide exchange with cystine to form a mixed disulfide of Thiola-cysteine. From this reaction, a water-soluble mixed disulfide is formed and the amount of sparingly soluble cystine is reduced.

The reduction in urinary cystine produced by Thiola^® is generally proportional to the dose. Thiola^® causes a sustained reduction in cystine excretion without apparent loss of effectiveness.

Therapeutic features

A limited study involving 66 cystinuric patients in the U.S. showed:

• With Thiola^®, fewer or less severe adverse reactions may be experienced.
• Thiola^® was effective in retarding the rate of new stone formation, causing a remission in 63-71% of patients and reduced individual stone formation in 81-94% of patients.
• Thiola^® was equally as effective as d-penicillamine in reducing cystine excretion. During long term treatment with Thiola^® (at 1000 mg/day) urinary cystine was maintained at 350-560 mg/day and urinary saturation of cystine was kept undersaturated.

About tiopronin

Tiopronin is N-(2-Mercaptopropionyl) glycine.

Tiopronin has the empirical formula C₅H₉NO₃S and a molecular weight of 163.20. In this drug product tiopronin exists as a dl racemic mixture. Tiopronin is a white crystalline powder which is freely soluble in water.

Thiola^® tablets are white, sugar coated tablets, each containing 100 mg of tiopronin and are taken orally.