Pharmacologic Class: Xanthine oxidase inhibitor
ACTIONS AND USES: Allopurinol is an older drug used to control the hyperuricemia that causes severe gout and to reduce the risk of acute gout attacks. It is also approved to prevent recurrent kidney stones in patients with elevated uric acid levels. It may be used prophylactically to reduce the severity of the hyperuricemia associated with antineoplastic and radiation therapies, both of which increase serum uric acid levels by promoting nucleic acid degradation. This drug takes 1 to 3 weeks to bring serum uric acid levels to within the normal range. Allopurinol is available by the PO and IV routes. IV administration is usually reserved for patients with high uric acid levels resulting from cancer chemotherapy.
ADMINISTRATION ALERTS: Give with or after meals. Tablets may be crushed and mixed with food or fluids. Pregnancy category C.
ADVERSE EFFECTS: The most frequent and serious adverse effects are dermatologic and include micropapular rash and rare cases of fatal toxic epidermal necrolysis and Stevens–Johnson syndrome. A rare, sometimes fatal, hypersensitivity syndrome may occur and includes a skin rash, fever, hepatitis, leukocytosis, and progressive renal failure. Other possible adverse effects include drowsiness, headache, vertigo, nausea, vomiting, abdominal discomfort, malaise, diarrhea, retinopathy, and thrombocytopenia.
Contraindications: Contraindications include hypersensitivity to allopurinol and idiopathic hemochromatosis. Use cautiously in patients with impaired hepatic or renal function, history of peptic ulcers, lower GI tract disease, bone marrow depression, and pregnancy.
INTERACTIONS Drug–Drug: Alcohol may inhibit the renal excretion of uric acid. Ampicillin and amoxicillin may increase the risk of skin rashes. An enhanced anticoagulant effect may be seen with the use of warfarin, and toxicity risks increase for azathioprine, mercaptopurine, cyclophosphamide, and cyclosporine. The risk of ototoxicity is increased when allopurinol is used with thiazides and angiotensin-converting enzyme (ACE) inhibitors. Aluminum antacids taken concurrently with allopurinol may decrease its effects. An increased effect may be seen with phenytoin and anticancer drugs, necessitating the need for altered doses of these medications.
RELATED;
1. GOUT
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