allopurinol is a prescription medication usedto treat gout, high levels of uric acid, and kidney stones. allopurinol belongs to a groupof drugs call xanthine oxidase inhibitors, which work by decreasing uric acid in thebody. high levels of uric acid may lead to gout attacks or kidney stones. this medicationcomes in tablet form and is taken once a day or in divided doses, with food and water.it is also in an injectable form to be given into the vein (iv) by healthcare professional.common side effects of allopurinol include diarrhea, nausea, and rash. allopurinol canalso cause drowsiness. do not drive or operate heavy machinery until you know how allopurinolaffects you. take this medication only as directed. for more information, download therxwiki mobile app.