Tiopronin

What is tiopronin?

Tiopronin is a drug used to prevent and dissolve cystine bladder stones in dogs. It is added to the treatment plan when other methods of creating an alkaline urine are not completely effective, such as dietary changes and increased fluid intake.

There are no licensed veterinary versions of tiopronin available. Human formulations may be prescribed for off-label use (Thiola®, Thiola EC®). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet tiopronin?

• Tiopronin is given orally (by mouth) and comes in the form of tablets.
• Tiopronin may also be compounded into other forms.
• Measure liquid compounded forms of this medication carefully.
• Ideally, give this medication at the same time each day.
• Give at least 1 hour before meals or 2 hours after meals.
• If vomiting occurs when dosed on an empty stomach, give future doses with food or a treat.
• Give tiopronin, along with increased water intake and dietary alteration, in accordance with your veterinarian’s directions.

This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly, so laboratory tests may be needed to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects from tiopronin?

Tiopronin may cause the following side effects:

• Dry crusty nose
• Urine that has a sulfur smell (like rotten eggs)
• Aggression
• Lethargy
• Skin sensitivity
• Slow wound healing
• Raised, pimple-like lesions on the skin

Serious adverse reactions associated with this drug may occur without warning and could, in rare cases, lead to death. If any of the following signs develop, stop giving tiopronin and contact your veterinarian immediately:

• Pale gums (indication of anemia)
• Staggering
• Difficulty chewing
• Protein in the urine (noted through urine testing)
• Low platelet levels (noted through blood testing)
• Increased thirst or urination

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of the treatment and notify your veterinarian if you have any concerns.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in animals with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE tiopronin in:

• Cats
• Pets that are pregnant or nursing
• Pets with an allergy to it
• Pets with a urinary tract blockage
• Pets with a history of agranulocytosis (very low white blood cells), aplastic anemia (a form of low red blood cells), or thrombocytopenia (low platelets)

USE WITH CAUTION in:

• Pets with poor liver or kidney function
• Pets that are sensitive to penicillin drugs

Are there any drug interactions I should be aware of?

There are no known drug interactions for tiopronin; however there may be increased risks of adverse effects when it is used with drugs that can cause liver, kidney, or bone marrow damage. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Regular rechecks are recommended at specific intervals after starting the drug, including a physical exam, urine tests, blood tests, and imaging of the urinary tract (X-rays, ultrasound). Follow your veterinarian’s directions.
• Your veterinary team will measure the amount of urinary cystine excretion before initiation of therapy and yearly after that.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store tiopronin?

• Ensure tiopronin is tightly stored in its original container in a cool, dry place and protected from light.
• Store this medication at room temperature between 68°F and 77°F (20°C–25°C).
• Keep the container out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet’s weight and symptoms.