Thiola (Tiopronin): 100 mg Tablets

Tiopronin (Thiola)


Highlights of Prescribing Information

  • Drug for prevention (& treatment) of cystine urolithiasis
  • Cautions: Agranulocytosis, aplastic anemia, thrombocytopenia or other significant hematologic abnormality, impaired renal or hepatic function, or sensitivity to either tiopronin or penicillamine
  • Adverse Effects: Coombs’-positive regenerative sphero-cyte anemia, aggressiveness, proteinuria, thrombocytopenia, elevations in liver enzymes, dermatologic effects, & myopathy

What Is Drug Used For?

Tiopronin is indicated for the prevention of cystine urolithiasis in patients where dietary therapy combined with urinary alkalinization is not completely effective. It may also be useful in combination with urine alkalinization to dissolve stones.

Pharmacology / Actions

Tiopronin is considered an antiurolithic agent. It undergoes thioldisulfide exchange with cystine (cysteine-cysteine disulfide) to form tiopronin-cystine disulfide. This complex is more water-soluble and is readily excreted thereby preventing cystine calculi from forming.


Tiopronin has a rapid onset of action and in humans, up to 48% of a dose is found in the urine within 4 hours of dosing. Tiopronin has a relatively short duration of action and its effect in humans disappears in about 10 hours. Elimination is primarily via renal routes.

Before you take Drug

Contraindications / Precautions / Warnings

Tiopronin’s risks versus its benefits should be considered before using in patients with agranulocytosis, aplastic anemia, thrombocytopenia or other significant hematologic abnormality, impaired renal or hepatic function, or sensitivity to either tiopronin or penicillamine.

Adverse Effects

There is limited information available on the adverse effect profile of tiopronin in dogs. While tiopronin is thought to have fewer adverse effects than penicillamine in humans, it has been associated with Coombs’-positive regenerative spherocyte anemia in dogs. Should this effect occur, the drug should be discontinued and appropriate treatment started (corticosteroids, blood component therapy as needed). Other adverse effects noted in dogs include aggressiveness, proteinuria, thrombocytopenia, elevations in liver enzymes, dermatologic effects, and myopathy.

Adverse effects noted in humans that occur more frequently include dermatologic effects (ecchymosis, itching, rashes, mouth ulcers, jaundice) and GI distress; less frequently allergic reactions (specifically adenopathy), arthralgias, dyspnea, fever, hematologic abnormalities, edema, and nephrotic syndrome have been noted.

Reproductive / Nursing Safety

There is limited information on the reproductive safety of tiopronin. Skeletal defects, cleft palates and increased resorptions were noted when rats were given 10 times the human dose of penicillamine and, therefore, may also be of concern with tiopronin. Other animal studies have suggested that tiopronin may affect fetus viability at high doses. In humans, the FDA categorizes this drug as category C for use during pregnancy (Animal studies have shown an adverse effect on the fetus, hut there are no adequate studies in humans; or there are no animal reproduction studies and no adequate studies in humans.)

Because tiopronin may be excreted in milk, at present it is not recommended for use in nursing animals.

Overdosage / Acute Toxicity

There is little information available. It is suggested to contact an animal poison control center for further information in the event of an overdose situation.

Drug Interactions

Potentially use of tiopronin with other drugs causing nephrotoxicity, hepatotoxicity, or bone marrow depression could cause additive toxic effects. Clinical significance is not clear.

How to use Drug

Drug dosage for dogs:

For treatment or prevention of recurrence of cystine urinary calculi:

  1. a) In conjunction with an alkalinizing, protein and sodium restricted diet (), 30-40 mg/kg PO divided into two daily doses. ()
  2. b) Treatment: 20 mg/kg PO twice daily for 1-3 months; relatively high incidence of adverse effects;

Prevention: 15 mg/kg PO twice daily. ()


■ Efficacy (stone size)

■ CBC with platelets

■ Liver enzymes

■ Urinalyses including urine pH

Client Information

■ Clients should be counseled on the importance of adequate compliance with this drug to maximize efficacy and detailed on the clinical signs to watch for regarding adverse effects.

Chemistry / Synonyms

A sulfhydryl compound related to penicillamine, tiopronin has a molecular weight of 163.2. It occurs as a white crystalline powder which is freely soluble in water.

Tiopronin may also be known as: SF 522, N-(2-Mercaptopropionyl)-glycine (MPG), 2-MPG, thiopronine, Acadione, Captimer, Epatiol, Mucolysin, Mucosyt, Sutilan, Thiola, Thiosol, or Tioglis.

Storage / Stability

Store tablets at room temperature in tight containers.

Dosage Forms / Regulatory Status

Veterinary-Labeled Products: None

Human-Labeled Products:

Tiopronin Tablets: 100 mg; Thiola (Mission); (Rx)


Selections from the book: “Plumb’s Veterinary Drug Handbook. Sixth Edition”. 2008