Allopurinol

Urate urolithiasis in dogs (especially Dalmatians); hyperuricemia; leishmaniasis in dogs (extralabel); xanthine oxidase inhibitor. Xanthine oxidase inhibitor. Mechanism: allopurinol (and its active metabolite oxipurinol) competitively inhibits xanthine oxidase, reducing conversion of hypoxanthine and xanthine to uric acid. Decreases uric acid production and plasma/urine urate levels. Also has immunomodulatory effects relevant to Leishmania treatment. Key information Store at room temperature. Do not use in Dalmatians — may precipitate xanthine urolithiasis. Increase water intake. Drug interaction: potentiates azathioprine — reduce azathioprine dose by 75% if used concurrently. Renal dosage adjustment required.

Oral tablets: Administer orally. May be given with food to improve compliance and reduce GI upset. Administer with food to reduce GI adverse effects. to reduce GI irritation. Ensure adequate water intake throughout therapy. Tablets may be crushed and mixed with food if needed. If a dose is missed Administer as soon as you remember. If it is almost time for the next scheduled dose, skip the missed dose and resume the normal schedule. Never double up doses to make up for a missed one.

GI: vomiting, diarrhea, anorexia. Dermatologic: skin rash, pruritus (discontinue if severe — hypersensitivity). Rare: hepatotoxicity (monitor liver enzymes). Xanthine urolithiasis (in Dalmatians — predisposed due to uric acid metabolism; allopurinol shifts to xanthine stones). Drug interaction: potentiates azathioprine/6-MP toxicity.

For animals Reduce dose or extend interval in renal impairment. — drug and metabolite accumulate in renal impairment; reduce dose. Monitor liver enzymes with prolonged use. Dalmatian dogs: may shift from urate to xanthine uroliths — monitor urine for xanthine crystals. Critical interaction: potentiates azathioprine and 6-mercaptopurine toxicity (myelosuppression) — reduce azathioprine dose to 25% when used concurrently. For people handling this medication Wash hands thoroughly with soap and water after handling. Avoid contact with eyes; if contact occurs, flush with water for 15 minutes and seek medical attention. Keep out of reach of children. If accidental ingestion occurs, contact Poison Control (1-800-222-1222). Keep out of reach of children. Pregnant women and women of childbearing age should avoid contact.

Contact your veterinarian. Allopurinol overdose causes GI signs and, in Dalmatians, xanthine crystals. Contact your veterinarian, a veterinary emergency clinic, or the ASPCA Animal Poison Control Center (888-426-4435) immediately. Do not induce vomiting unless specifically directed by a veterinary professional.