Allopurinol for Dogs - Uses, Dose and Side Effects

Josie F. Turner
By Josie F. Turner, Journalist specialized in Animal Welfare. Updated: February 16, 2020
Allopurinol for Dogs - Uses, Dose and Side Effects

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Allopurinol is a drug that is used in human medicine to reduce the level of uric acid in blood plasma and urine. Doing so inhibits the particular enzyme involved in its formation. In veterinary medicine, this is a drug which is used in combination with drugs such as miltefosine which is administered to treat leishmaniasis. This is especially the case with allopurinol for dogs.

If your veterinarian has prescribed allopurinol for your dog, you may want to know a little more about it. While its uses and dose should be explained by the veterinarian, it is possible you may not be aware of its side effects. Keep reading to find out more.

  1. What is allopurinol and what is its uses?
  2. Alopurinol for dogs with leishmaniasis
  3. Allopurinol dose in dog
  4. Side effects of allopurinol in dogs
  5. Alternatives to allopurinol for dogs

What is allopurinol and what is its uses?

Allopurinol is an enzyme inhibitor. Specifically, it inhibits the enzyme which metabolizes the conversion of the purine base xanthine to uric acid. It is not used on its own, but is an adjunct treatment to the main drug which is a leishmanicide. This is usually miltefosine, a drug sold under the trade name Impavido among others. This works to remove all the parasites from the dog's tissues. This is why allopurinol is used to treat leishmaniasis, but it is not used on its own.

This drug is administered orally and its treatment can last between 6 months to a year. There are even case when treatment can last even longer. Regardless, a review and follow-up examination is required once treatment is established. This will take into account the severity of each case of parasitosis, as well as other factors which affect the clinical picture of the individual dog.

Allopurinol treatment should be customized to the specific patient. For example, a daily administration of miltefosine for approximately one month will be combined with a daily allopurinol treatment for about 8 months.

Alopurinol for dogs with leishmaniasis

As we have stated above, allopurinol is used in the treatment against leishmaniasis. This is a type of parasitic disease caused by the protozoa leishmania. This internal parasite is found in the Phlebotominae family of mosquitos which act as their vector. It is a zoonotic disease meaning it can be transferred to humans. it has a worldwide distribution, although it is more prevalent in certain regions. It is of a serious nature, so prevention is vital. Prevention methods include flea collars, vaccinations and deworming schedules.

Dogs infested with leishmania will show certain signs and symptoms, but diagnosis will need to be carried out by a veterinarian as it requires a laboratory diagnosis. It is a non-specific disease as it can display various symptoms which are shared by various other medical conditions. This is why it is always important to look at the context of the dog's symptoms, including the epidemiology of the disease in the dog's local area.

Some symptoms of leishmaniasis include:

  • Hair loss
  • Crusted sores
  • Hardened mucus membranes
  • Nodules
  • Suden weight loss
  • Anemia
  • Chronic diarrhea
  • Pneumonia

It is common that, in addition to leishmaniasis, the dog will suffer from other parasitic blood diseases. This is closely linked to the level of antiparasitic protection used in the dog. We should start treating the leishmaniasis only once we have the dog stabilized. If the dog has anemia, kidney failure, dermatitis or other problems related to the infestation, we need to ensure these are stable before removing the parasite itself. If we don't, the treatment can exacerbate them.

Miltefosine and other leishmanicidal drugs (those which eliminate the parasite) are intensified with the use of allopurinol in dogs. However, due to potentially adverse side effects of allopurinol, some veterinarians are looking for alternatives to this drug.

Allopurinol for Dogs - Uses, Dose and Side Effects - Alopurinol for dogs with leishmaniasis

Allopurinol dose in dog

The dose of allopurinol for dogs that is established for the treatment of leishmaniasis is 10 mg per kg of weight every 12 hours. This means the treatment will need to be administered twice daily.

The pharmacological availability of oral allopurinol are generally 100 mg and 300 mg allopurinol tablets,. Our veterinarian will work out how many pills we should administer according to the weight of our dog. Also, remember that it must be the specialist who determines the duration of the treatment. We should never stop treatment without the specific instruction of our veterinarian. Doing so may mean the parasites are not removed from the dog's tissues.

Side effects of allopurinol in dogs

There are two main side effects that allopurinol can cause in dogs that take it:

  • Xanthinuria: when purine bases are degraded by the corresponding enzyme, xanthine is created. In turn, this is transformed into uric acid. Allopurinol interferes with the transformation of xanthine into uric acid which must be eliminated by the urine. For this reason, an excess of xanthine may occur.
  • Urolithiasis: excess xanthine crystals can produce accumulations of organic matter and form uroliths (bladder stones). These uroliths are radiolucent. This means they are not observed with a simple x-ray and a contrast x-ray or ultrasound will be required to diagnose them.

The clinical signs that can be observed with these pathologies are:

Today we can find feed for dogs made specifically for the treatment of leishmaniasis. They are characterized by their low purine content, thus helping to prevent the formation of xanthine crystals. In addition, they present substances that help in the protection of the joints, skin and immunity.

Allopurinol for Dogs - Uses, Dose and Side Effects - Side effects of allopurinol in dogs

Alternatives to allopurinol for dogs

As we have mentioned in previous sections, the side effects of allopurinol have led many veterinarians to choose to look for alternatives to this drug. For this reason, a recent study confirms that impromune a nucleotide-based nutraceutical, is effective against the progress of leishmania and does not appear to generate unwanted effects.

This new trend in leishmaniasis treatment leads us better protecting our animals from dangerous parasitical disease. The main drawback is that it is a higher cost drug in respect to allopurinol. For this reason, it is possible your veterinarian will prescribe according to your financial standing.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Allopurinol for Dogs - Uses, Dose and Side Effects, we recommend you visit our Medicine category.


1. Segarra, S., et al. (2017). Randomized, Allopurinol-Controlled Trial of the Effects of Dietary Nucleotides and Active Hexose Correlated Compound in the Treatment of Canine Leishmaniosis. Veterinary Parasitology, 239, 50-56.

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1 comment
Darlene Colley
I have 18mo male German Shepherd that keeps getting severe UTI’s . My vets can’t figure out why. They told me I may have to put him down. HELP
Administrador AnimalWised
Hello Darlene,

We are so sorry to hear this. Unfortunately, we can't provide any diagnostic information. The veterinarian is a professional and their assessment needs to be respected. In saying that, if you feel like your dog isn't getting the right treatment, we recommend going to a different vet and getting a second opinion
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Allopurinol for Dogs - Uses, Dose and Side Effects