Allopurinol

Allopurinol: Uses, Dosage and Side Effects

Overview

Its action depends on preventing the conversion of hypoxanthine to xanthine and of xanthine to uric acid, xanthine oxidase inhibition reduces the production of uric acid.

Uses of Allopurinol

• Treatment and prevention of canine hyperuricosuric, calcium oxalate urolithiasis and recurring uric acid uroliths.
• To treat leishmaniosis in conjunction with miltefosine or meglumine antimonite.
• In patients with compromised renal function, use with caution.

Dose of Allopurinol in Dogs and Cats

Cats:

• 10-20 mg/kg orally q12-24h has been demonstrated to be beneficial for treating leishmaniosis (although experience is limited in this species).

Dogs 

uric acid urolithiasis:

• Dissolution: 10 mg/kg or 15 mg/kg orally every eight hours or every 12 hours for up to 4 weeks.
• Prevention: 10-15 mg/kg PO every 24 hours.

Leishmaniosis: 10 mg/kg orally every 12 hours for at least 6–12 months, with meglumine antimonate for 1–2 months, or miltefosine for 1 month (NB: this does not completely cure the parasite).

Side Effects of Allopurinol in Dogs and Cats

• Increasing the risk of developing xanthine urolithiasis, especially if used for a long time and not fed a purine-restricted diet.

Contraindications of Allopurinol in Dogs and Cats

Allopurinol is contraindicated in patients with previous hypersensitivity reactions and should be used with caution in patients with hepatic or renal dysfunction.

Some Notes:

• In humans, allopurinol may enhance the effects of azathioprine and theophylline
• It is recommended to avoid administering Allopurinol with these drugs due to the occurrence of interactions between each other:
  • Aluminum hydroxide:  decreases absorption of allopurinol.
  • Cyclophosphamide: increase the risk for bone marrow suppression.
  • Cyclosporines: increase in cyclosporine concentration may occur.
  • Uricosuric agents ( probenecid, sulfinpyrazone):  increase the renal excretion of oxypurinol and thereby reduce xanthine oxidase inhibition.
  • Urinary acidifiers (Eg, ammonium chloride, methionine):  reduce the solubility of uric acid in the urine and induce urolithiasis.