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Pharmacologic class: Xanthine oxidase inhibitor
Therapeutic class: Antigout drug
Pregnancy risk category C
Inhibits conversion of xanthine to uric acid and increases reutilization of hypoxanthine and xanthine for nucleic acid synthesis, thereby decreasing uric acid levels in both serum and urine
Powder for injection: 500-mg vial
Tablets: 100 mg, 300 mg
⊘Indications and dosages
➣ Gout in patients with frequent disabling attacks; gout resulting from hyperuricemia, acute or chronic leukemia, psoriasis, or multiple myeloma
Adults: 200 to 300 mg P.O. daily in mild cases or 400 to 600 mg P.O. daily in severe cases, to a maximum dosage of 800 mg/day; or 200 to 400 mg/m2/day I.V. as a single infusion or in equally divided doses q 6, 8, or 12 hours to a maximum dosage of 600 mg/day
Children ages 6 to 10: 300 mg P.O. daily
Children younger than age 6: 150 mg P.O. daily
➣ To prevent acute gout attacks Adults: 100 mg P.O. daily; increase by 100 mg at weekly intervals without exceeding maximum dosage of 800 mg, until uric acid level falls to 6 mg/dl or less
➣ Recurrent calcium oxalate calculi
Adults: 200 to 300 mg P.O. daily in single dose or divided doses
➣ To prevent uric acid nephropathy during cancer chemotherapy
Adults: 600 to 800 mg P.O. daily for 2 to 3 days, accompanied by high fluid intake
• Renal impairment
• Hematemesis caused by gastritis induced by nonsteroidal anti-inflammatory drugs
• Pain from acute pancreatitis
• Seizures refractory to standard therapy
• Hypersensitivity to drug
Use cautiously in:
• acute gout attack, renal insufficiency, dehydration
• pregnant or breastfeeding patients.
• Reconstitute single-dose vial with 25 ml sterile water for injection. Further dilute with normal saline solution or D5W to a concentration of 6 mg/ml or less.
• Infuse over 30 to 60 minutes.
• Don't mix I.V. form with other drugs or give through same I.V. port as drugs that may be incompatible.
• Divide oral doses larger than 300 mg.
• Give oral form with or right after meals.
• Don't give oral form with mineral water, orange juice, or caffeinated beverages.
CNS: drowsiness, dizziness, headache, peripheral neuropathy, neuritis, paresthesia
CV: hypersensitivity vasculitis, necrotizing vasculitis
EENT: retinopathy, cataract, epistaxis
GI: nausea, vomiting, diarrhea, abdominal pain, dyspepsia, gastritis
GU: exacerbation of gout and renal calculi, uremia, renal failure
Hematologic: eosinophilia, anemia, thrombocytopenia, bone marrow depression, agranulocytosis, leukocytosis, aplastic anemia, leukopenia
Hepatic: cholestatic jaundice, hepatomegaly, hepatitis, hepatic necrosis
Musculoskeletal: myopathy, joint pain
Skin: rash; alopecia; maculopapular, urticarial, or purpuric lesions; severe furunculosis of nose; ichthyosis; bruising; scaly or exfoliative erythema multiforme; toxic epidermal necrolysis
Other: abnormal taste, loss of taste, fever, chills
Drug-drug.Amoxicillin, ampicillin, bacampicillin: increased risk of rash
Anticoagulants (except warfarin): increased anticoagulant effect
Antineoplastics: increased risk of myelosuppression
Azathioprine, mercaptopurine: inhibition of allopurinol metabolism
Chlorpropamide: increased hypoglycemic effects
Diazoxide, diuretics, mecamylamine, pyrazinamide: increased uric acid levels
Ethacrynic acid, thiazide diuretics: increased risk of allopurinol toxicity
Uricosurics: increased uric acid excretion
Urine-acidifying drugs (ammonium chloride, ascorbic acid, potassium or sodium phosphate): increased risk of renal calculi
Xanthines: increased theophylline levels
Drug-diagnostic tests.Alanine aminotransferase, alanine phosphatase, aspartate aminotransferase, bilirubin, eosinophils: increased levels
Granulocytes, hemoglobin, platelets, white blood cells: decreased levels
Drug-food.Caffeine-containing beverages and foods, mineral water, orange juice: decreased drug absorption, increased uric acid level
Drug-behaviors.Alcohol use: increased uric acid level
• Assess fluid intake and output. Intake should be sufficient to yield daily output of at least 2 L of slightly alkaline urine.
• Monitor uric acid level to help evaluate drug efficacy.
☞ Instruct patient to promptly report painful urination, bloody urine, rash, eye irritation, or swelling of lips and mouth.
• Tell patient to take drug with food or milk, exactly as prescribed.
• Explain that gout attacks may not ease significantly until 2 to 6 weeks of therapy.
• Caution patient to avoid driving and other hazardous tasks until he knows how drug affects concentration and alertness.
• Advise patient to avoid alcohol, caffeine-containing beverages and foods, mineral water, and orange juice during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, and behaviors mentioned above.