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Allopurinol by Qualitest Pharmaceuticals, Inc.

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General Description:

This drug inhibits an enzyme resulting in a decrease in the amount of uric acid produced in the body. Allopurinol is available in tablets.

What is this drug?
  • A xanthine oxidase inhibitor
  • Given by mouth
Reasons for prescribing:
  • To prevent formation of urate bladder stones
  • An alternative treatment for Leishmania and Trypanosoma parasites
What dogs/cats should not take this medication?
  • Animals with liver or kidney disease
  • Animals that may be pregnant or nursing
  • Animals with a known hypersensitivity or allergy to this drug should not take this medication

Read and follow the prescription label carefully.

Give the exact amount prescribed and only as often as directed.

Give this medication for as long as your veterinarian directs. Do not skip doses or stop giving the medication without consulting your veterinarian.

Baseline blood work and urinalysis are recommended to assess your pet's general health before starting this drug.

Periodic blood work and follow-up urinalysis are required to monitor allopurinol's effect on the body as long-term therapy is often necessary.

Dose adjustments may be made based upon these results and an assessment of how your dog or cat is responding clinically.

Call ahead for refills.

Ideally, give medication at the same time(s) daily.

This medication is often given in conjunction with a low purine diet to avoid formation of other bladder stones.

What if a dose is missed?

If a dose is missed, give it as soon as you can. If it is time already for the next dose, skip the missed dose and go back to the normal schedule. Do not give two doses at the same time.

What to tell/ask a veterinarian before giving medication?

Talk to your veterinarian about:

  • When your pet will need to be rechecked
  • What tests may need to be performed prior to and during treatment with this drug
  • What are the risks and benefits of using this drug

Tell your veterinarian about:

  • If your pet has experienced side-effects on other drugs/products
  • If your pet has experienced digestive upset now or ever
  • If your pet has experienced liver or kidney disease now or ever
  • If your pet has experienced any other medical problems or allergies now or ever
  • All medicines and supplements that you are giving your pet or plan to give your pet, including those you can get without a prescription. Your veterinarian may want to check that all of your pet's medications can be given together.
  • If your pet is pregnant, nursing or if you plan to breed your pet
Storage and Warnings:

Allopurinol should be stored in a childproof container in a cool, dry place at room temperature away from heat and direct sunlight.

Keep this and all medication out of reach of children and pets.

Call your physician immediately if you accidentally take this product.

Potential side effects:

Chronic use of this medication without proper attention to diet can cause xanthine bladder stones and possible difficulty with urinating
This medication can affect the gastrointestinal system causing nausea, vomiting, cramping, and diarrhea
This medication can affect the liver
This medication can affect the skin causing hives, itchiness, or a rash
This medication can cause bone marrow suppression
If these symptoms persist or you notice anything else unusual, contact your veterinarian

Can this drug be given with other drugs?

Yes, but possible interactions may occur when giving allopurinol in conjunction with: certain diets, aminophylline, ammonium chloride, amoxicillin, ampicillin, azathioprine, cyclophosphamide, furosemide, methionine, theophylline, trimethoprim/sulfas, and oral anticoagulants like warfarin
Drugs other than those listed may also interact with allopurinol
Do not give new food or medications without first talking to your veterinarian
If your pet experiences any unusual reactions when taking multiple medications, contact your veterinarian


Contact your veterinarian immediately if your pet receives more than the prescribed amount.

What else should I know?

Notify your veterinarian if your animal's condition does not improve or worsens despite this treatment.

As with all prescribed medicines, allopurinol should only be given to the pet for which it was prescribed.

It should be given only for the condition for which it was prescribed.

This is just a summary of information about allopurinol. If you have any questions or concerns about allopurinol or the condition it was prescribed for, please contact your veterinarian.

(Aloprim, Zyloprim)

Common Drug Name

Common Brand Names
Aloprim and Zyloprim
Generic products are available.

Store at room temperature in a tight, light resistant, childproof container.

Allopurinol decreases the amount of uric acid produced in the body. It is often used in conjunction with a change in diet that is low in purines. The pet is usually on the medication for life.
Dogs: Allopurinol is used in the prevention of urate urinary (bladder) stones. It is also used in the treatment of infection with the blood parasites Leishmania and Trypanosoma sp.
Cats: Allopurinol is used in the prevention of urate urinary (bladder) stones. 
Birds and Reptiles: It is used in the treatment of gout.

Dose and Administration
Always follow the dosage instructions provided by your veterinarian.  If you have difficulty giving the medication, contact your veterinarian.
In mammals, dose is adjusted based on a 24-hour urine urate excretion test. Spot tests (single urine samples) are inaccurate. Consult with your veterinarian regarding the laboratory testing necessary during treatment with allopurinol.
Dogs and Cats: Usually given after a meal, unless directed otherwise by your veterinarian.
Birds and Reptiles: Usually given in the drinking water. Make fresh solutions daily. If you miss a dose, give it as soon as you remember. If it is almost time for the next dose, skip the one you missed and go back to the regular schedule. Do not give 2 doses at once.
This medication should only be given to the pet for whom it was prescribed.

Possible Side Effects
Side effects are rare in animals, but in humans may see nausea, cramping, vomiting, or diarrhea; bone marrow suppression, which could result in anemia, increased risk of infection, and bleeding problems; tiredness; skin rashes; liver damage; and vasculitis (inflammation of blood vessels). If given in excess, may see formation of other types of bladder stones.
Consult your veterinarian if you notice any of the above side effects.
Although rare, if your pet experiences an allergic reaction to the medication, signs may include facial swelling, hives, scratching, sudden onset of diarrhea, vomiting, shock, seizures, pale gums, cold limbs, or coma. If you observe any of these signs, contact your veterinarian immediately.

Not for use in animals hypersensitive (allergic) to allopurinol, or who have had a serious reaction to it.
Use with caution, lower doses, and intense The safety of this medication in breeding, pregnant, and lactating animals (female animals nursing their young) has not been determined.
With prolonged use, your veterinarian may decrease the dose to help prevent formation of other types of bladder stones.
Consult with your veterinarian regarding physical examinations and laboratory testing necessary prior to and during treatment with allopurinol.

Drug, Food, and Test Interactions
Consult your veterinarian before using allopurinol with vitamins, supplements, cyclophosphamide, probenecid, sulfinpyrazone, diuretics (e.g., furosemide, Salix, Lasix), aminophylline, theophylline, azathioprine, warfarin, mercaptopurine, trimethoprim/sulfamethoxazole, urine acidifiers (such as methionine and ammonium chloride), and with food meant to acidify the urine or with food high in purine.  
In humans, skin rashes were more common if given with amoxicillin or ampicillin. Low platelet counts have occurred when given with trimethoprim/sulfamethoxazole.

Signs of Toxicity/Overdose
Chronic overdoses cause the formation of different types of bladder stones and could cause difficulty urinating.  If you know or suspect your pet has had an overdose, or if you observe any of these signs in your pet, contact your veterinarian immediately.
Keep this and all other medications out of the reach of children and pets.
monitoring in animals with liver or kidney disease.

This information may not cover all possible uses, directions, side effects, precautions, allergic reactions, drug interactions, or withdrawal times.  Always consult your own veterinarian for specific advice concerning the treatment of your pet.


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