Allopurinol

Allopurinol, sold under the brand name Zyloprim among others, is a medication used to decrease high blood uric acid levels. It is specifically used to prevent gout, prevent specific types of kidney stones and for the high uric acid levels that can occur with chemotherapy. It is taken by mouth or injected into a vein. Allopurinol, sold under the brand name Zyloprim among others, is a medication used to decrease high blood uric acid levels. It is specifically used to prevent gout, prevent specific types of kidney stones and for the high uric acid levels that can occur with chemotherapy. It is taken by mouth or injected into a vein. Common side effects when used by mouth include itchiness and rash. Common side effects when used by injection include vomiting and kidney problems. While not recommended historically, starting allopurinol during an attack of gout appears to be safe. In those already on the medication, it should be continued even during an acute gout attack. While use during pregnancy does not appear to result in harm, this use has not been well studied. Allopurinol is in the xanthine oxidase inhibitor family of medications. Allopurinol was approved for medical use in the United States in 1966. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Allopurinol is available as a generic medication. The wholesale cost in the developing world is about US$0.81–3.42 per month. In the United States a month of treatment costs less than $25. In 2016 it was the 52nd most prescribed medication in the United States with more than 15 million prescriptions. Allopurinol is used to reduce urate formation in conditions where urate deposition has already occurred or is predictable. The specific diseases and conditions where it is used include gouty arthritis, skin tophi, kidney stones, idiopathic gout; uric acid lithiasis; acute uric acid nephropathy; neoplastic disease and myeloproliferative disease with high cell turnover rates, in which high urate levels occur either spontaneously, or after cytotoxic therapy; certain enzyme disorders which lead to overproduction of urate, for example: hypoxanthine-guanine phosphoribosyltransferase, including Lesch–Nyhan syndrome; glucose 6-phosphatase including glycogen storage disease; phosphoribosyl pyrophosphate synthetase, phosphoribosyl pyrophosphate amidotransferase; adenine phosphoribosyltransferase. It is also used to treat kidney stones caused by deficient activity of adenine phosphoribosyltransferase. Allopurinol was also commonly used to treat tumor lysis syndrome in chemotherapeutic treatments, as these regimens can rapidly produce severe acute hyperuricemia, although it has gradually been replaced by urate oxidase therapy. Intravenous formulations are used in this indication when people cannot take medicine by mouth. Allopurinol cotherapy is used to improve outcomes for people with inflammatory bowel disease and Crohn's disease who do not respond to thiopurine monotherapy. Cotherapy has also been shown to greatly improve hepatoxicity side effects in treatment of IBD. Cotherapy invariably requires dose reduction of the thiopurine, usually to one-third of the standard dose depending upon the patient's genetic status for thiopurine methyltransferase. Because allopurinol is not a uricosuric, it can be used in people with poor kidney function. However, allopurinol has two important disadvantages. First, its dosing is complex. Second, some patients are hypersensitive to the drug, therefore its use requires careful monitoring.