By Rania Gollakner, BS, DVM, MPH

What is ponazuril?

Ponazuril (brand names: Toltrazuril sulfone®, Marquis®, Ponalrestat®) is an antiprotozoal medication 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, coccidia, and Neospora caninum.

While it is labeled for use in horses, it is also used in cats, dogs, rabbits, birds, and reptiles to treat protozoal parasites ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. 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 given?

Ponazuril is given by mouth in the form of a paste. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure doses carefully.

This medication should take effect within 1 to 2 days; however, effects may not be visibly obvious and therefore laboratory tests may need to be done to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are uncommon but may include soft stools. Serious side effects include mouth/nose blisters, skin rash/hives, diarrhea, or seizures. Dogs that are predisposed to dry eye (keratoconjunctivitis sicca) may develop the condition after using this medication; watch for red eyes, eye discharge, and squinting.

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?

Ponazuril should not be used in pets that are allergic to it. It should be used cautiously in pregnant or lactating pets as safety has not been established. Ponazuril should be cautiously in dogs with dry eye (keratoconjunctivitis sicca), and in dog breeds susceptible to the condition, 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 drug interactions reported at this time. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working.

How do I store ponazuril?

Store the paste at room temperature between 68°F and 77°F (20°C and 25°C) and 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.

Related Articles