Allopurinol
Allopurinol 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 orally (by mouth) or intravenously (injected into a vein).
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| Trade names | Zyloprim, Caplenal, Zyloric, others |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682673 |
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| Routes of administration | Oral, intravenous |
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| Bioavailability | 78±20% |
| Protein binding | Negligible |
| Metabolism | Liver (80% oxipurinol, 10% allopurinol ribosides) |
| Elimination half-life | 2 h (oxipurinol 18–30 h) |
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| ECHA InfoCard | 100.005.684 |
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| Formula | C5H4N4O |
| Molar mass | 136.114 g·mol−1 |
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Common side effects when used orally 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. Allopurinol is available as a generic medication. In 2021, it was the 40th most commonly prescribed medication in the United States, with more than 15 million prescriptions.