Ponazuril or Toltrazuril

What is ponazuril or toltrazuril?

Ponazuril (brand name Marquis®) and toltrazuril (brand name BayCox®) are very similar antiprotozoal medications used to treat equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. It may also be used to treat other protozoal parasites such as Toxoplasma spp., Cystoisospora spp. (coccidia), and Neospora caninum.

While ponazuril is labeled for use in horses, ponazuril and toltrazuril are considered off label (extra-label) for treatment of protozoal parasites in cats, dogs, rabbits, birds, and reptiles. 

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 FDA or Health Canada. In these instances, follow your veterinarian’s directions and cautions very carefully, as their directions may be significantly different from those on the label.

How is ponazuril or toltrazuril given?

• Ponazuril is given by mouth, in the form of a paste, while toltrazuril is a liquid formulation given by mouth.
• Measure doses carefully.
• Both medications may be given with or without food.
• If vomiting occurs when dosed on an empty stomach, give future doses with food.

This medication should take effect within 1 to 2 days; however, effects may not be noted outwardly, and 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?

Ponazuril or toltrazuril may cause the following side effects:

• Soft stools

Serious adverse reactions may occur. If any of the following signs develop, stop giving ponazuril or toltrazuril and contact your veterinarian immediately:

• Mouth/nose blisters
• Skin rash/hives
• Diarrhea
• Seizures

Dogs may develop dry eye (keratoconjunctivitis sicca) after using this medication, if they are predisposed to it. Watch for red eyes, eye discharge, and squinting.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE ponazuril in:

• Pets that are allergic to it

USE WITH CAUTION in:

• Pregnant or lactating pets (safety has not been established)
• Dogs with dry eye (keratoconjunctivitis sicca)
• Dog breeds susceptible to dry eye (keratoconjunctivitis sicca), such as cocker spaniels, West Highland terriers, bulldogs, lhasa apsos, and shih tzus.

Are there any drug interactions I should be aware of?

There are no documented drug interactions for this medication. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• 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 ponazuril or toltrazuril?

• Store ponazuril or toltrazuril at room temperature between 68°F and 77°F (20°C and 25°C).
• Protect from light.

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.