Allopurinol

Trade Names:Aloprim- Powder for injection, lyophilized 500 mg

Trade Names:Zyloprim- Tablets 100 mg- Tablets 300 mg

Pharmacology

Inhibits xanthine oxidase, the enzyme responsible for conversion of hypoxanthine to xanthine and then to uric acid.

Pharmacokinetics

Absorption

About 90% absorbed from GI tract. T _max is 1.5 h (allopurinol) and 4.5 h (oxipurinol). C _max is 3 mcg/mL (allopurinol 300 mg) and 6.5 mcg/mL (oxipurinol).

Metabolism

Rapidly oxidized to oxipurinol.

Elimination

About 20% is excreted in the feces. Allopurinol is essentially cleared by glomerular filtration, whereas oxipurinol is reabsorbed in the kidney tubules. T _1/2 , plasma is about 1 to 2 h (allopurinol) and about 15 h (oxipurinol).

Onset

Uric acid decreases in about 2 to 3 days.

Peak

May require a week or more of treatment.

Duration

Xanthine oxidase inhibition is maintained over 24 h; however, uric acid levels may not return to pretreatment levels until 7 to 10 days following cessation of therapy.

Indications and Usage

Treatment of primary or secondary gout, hyperuricemia resulting from chemotherapy for malignancies, recurrent calcium oxalate renal calculi.

Management of patients with leukemia, lymphoma, and solid tumor malignancies when concurrently receiving cancer therapy that causes elevations of serum and urinary uric acid levels. Use injection in patients who cannot tolerate oral therapy.

Unlabeled Uses

Prevention of fluorouracil-induced stomatitis and fluorouracil-induced granulocyte suppression.

Contraindications

Standard considerations.

Dosage and Administration

PO 100 to 800 mg/day. For amounts over 300 mg, give divided doses.

PO 300 mg/day.

PO 150 mg/day.

PO 600 to 800 mg/day for 2 to 3 days.

PO 100 mg/day, increased by 100 mg at weekly intervals until adequate response is achieved or max recommended dose (800 mg/day) is reached.

IV 200 to 400 mg/m ² /day (max 600 mg/day).

IV Starting dose 200 mg/m ² /day.

200 mg/day.

No more than 100 mg/day.

100 mg/day at extended intervals.

Alternatively, for CrCl greater than 50 mL/min, use 75% of usual daily dose; CrCl 10 to 50 mL/min, use 50% of usual daily dose; CrCl less than 10 mL/min, use 25% of usual daily dose.

200 mg/day.

100 mg/day.

100 mg/day at extended intervals.

Alternatively, for CrCl greater than 50 mL/min, use 75% of usual daily dose; CrCl 10 to 50 mL/min, use 50% of usual daily dose; CrCl less than 10 mL/min, use 25% of usual daily dose.

PO/IV Administer 50% of supplemental dose after dialysis. For continuous renal replacement therapy, dose as for CrCl 10 to 50 mL/min.

Storage/Stability

Store reconstituted solution at 20° to 25°C; do not refrigerate or dilute product.

Store tablets in tightly closed container in cool location.

Store unreconstituted powder at room temperature.

Drug Interactions

May lessen effectiveness of allopurinol.

May increase incidence of ampicillin-induced skin rash.

May enhance bone marrow suppression.

Theophylline Cl may be decreased, leading to toxicity.

Toxicity of these drugs may be increased.

amikacin; amphotericin B; carmustine; cefotaxime; chlorpromazine; cimetidine; clindamycin; cytarabine; dacarbazine; daunorubicin; diphenhydramine; doxorubicin; doxycycline; droperidol; floxuridine; gentamicin; haloperidol; hydroxyzine; idarubicin; imipenem plus cilastatin; mechlorethamine; meperidine; metoclopramide; methylprednisolone sodium succinate; minocycline; nalbuphine; netilmicin; ondansetron; prochlorperazine edisylate; promethazine; sodium bicarbonate; streptozocin; tobramycin; vinorelbine tartrate.

Laboratory Test Interactions

None well documented.

Adverse Reactions

CNS

Drowsiness; generalized seizure (injectable); headache; neuritis; paresthesias; peripheral neuropathy.

Dermatologic

Allergic vasculitis; alopecia; ecchymosis; skin rash. Allergic reactions may be severe and sometimes fatal.

EENT

Epistaxis; myopathy; taste disturbance.

GI

Abdominal pain; diarrhea; dyspepsia; gastritis; granulomatous changes; nausea; vomiting.

Genitourinary

Renal failure; uremia.

Hematologic

Bone marrow depression; eosinophilia; leukocytosis; leukopenia; thrombocytopenia.

Hepatic

Cholestatic jaundice; elevated liver enzymes; hepatic necrosis; hepatitis; reversible hepatomegaly.

Other

Acute gouty attacks; arthralgia; fever; myopathy; necrotizing angiitis.

Precautions

Pregnancy

Category C .

Lactation

Excreted in breast milk.

Children

Allopurinol is rarely indicated for use in children, except for hyperuricemia resulting from malignancy or with certain rare inborn errors of purine metabolism.

Hypersensitivity

Discontinue drug at first appearance of skin rash or other signs of allergic reaction. Rash may be followed by more severe hypersensitivity reactions and, rarely, death.

Renal Function

Reduced dose is given in patients with this condition. Drug may exacerbate renal failure in certain patients.

Acute gouty attacks

May occur during initial stages of therapy.

Bone marrow depression

Reported in patients given allopurinol.

Patient Information

• Encourage patient to focus on weight loss or control.
• Tell patient to avoid purine-rich foods (eg, organ meats).
• Caution patient to avoid excessive intake of alcohol.
• Explain that gouty attacks may not end for 2 to 6 wk after beginning therapy.
• Instruct patient to stop taking medication and notify health care provider if rash or flu-like symptoms develop.
• Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.

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